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The resonantly-stabilized cyclopentadienyl radical (C 5 H 5) is a key species in the combustion and molecular growth kinetics of mono and poly-aromatic hydrocarbons (M/PAHs). At intermediate-to-low temperatures, the C 5 H 5 reaction with the hydroperoxyl radical (HO 2) strongly impacts the competition between oxidation to smaller products and growth to PAHs, precursors of soot. However, literature estimates for the HO 2 + C 5 H 5 reaction rate are inaccurate and inconsistent with recent theoretical calculations, thus generating discrepancies in global combustion kinetic models. In this work, we perform state-of-the-art theoretical calculations for the HO 2 + C 5 H 5 reaction including variable reaction coordinate transition state theory for barrierless channels, accurate thermochemistry, and multi-well master equation (ME) simulations. Contrary to previous studies, we predict that OH + 1,3-C 5 H 5 O is the main reaction channel. The new rate constants are introduced in two literature kinetic models exploiting our recently developed ME based lumping methodology and used to perform kinetic simulations of experimental data of MAHs oxidation. It is found that the resonantly-stabilized 1,3-C 5 H 5 O radical is the main C 5 H 5 O isomer, accumulating in relevant concentration in the system, and that the adopted lumping procedure is fully consistent with results obtained with detailed kinetics. The reactivity of C 5 H 5 O with OH and O 2 radicals is included in the kinetic mechanisms based on analogy rules. As a result, C 5 H 5 O mostly reacts with O 2 producing smaller C 3 /C 4 species and large amounts of C 5 H 4 O, suggesting that further investigations of the reactivity of both C 5 H 5 O and C 5 H 4 O with oxygenated radicals is necessary. Overall, this work presents new reliable rate constants for the HO 2 + C 5 H 5 reaction and provides indications for future investigations of relevant reactions in the sub-mechanisms of cyclopentadiene and MAH oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] Mononuclear [CpNd(BH 4) 2 L] borohydrides comprising L = 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me 3 tach) and L = 1,4,7-trimethyl-1,4,7-triazacyclononane (Me 3 tacn) were obtained and structurally characterized. Their catalytic activity in coordination–insertion ring-opening poly-merization of ε-caprolactone was studied. [ABSTRACT FROM AUTHOR]

• Metal-ligand bonding in lanthanide(III) complexes is ionic in nature • Quantitative calculations reveal that metal-ligand bonding in lanthanide-metallocene complexes has a very significant covalent contribution • Metal-ligand covalency in lanthanide metallocene complexes involves the vacant lanthanide 6 s , 5 d and 6 p shells [Display omitted] Metal-ligand bonding in bis(cyclopentadienyl) and bis(cyclobutadienyl) lutetium(iii) complexes was studied in a variety of geometries using density functional theory. Based on analysis of the orbitals, the Morokuma–Ziegler–Rauk extended transition state method and natural orbitals of the chemical valence, the bonding interaction is dominantly ionic with a very important covalent contribution. The relative contribution of covalency is so large that it should not be neglected even in qualitative treatments of the electronic structure. The covalency arises from electron donation from the ligand HOMOs and HOMO–1 orbitals to the vacant 5 d , 6 s and 6 p orbitals at the Lu 3 + ion. While 5 d and the 6 s orbitals play the most important part, the 6 p orbitals also make a comparable contribution. A similar bonding picture emerges both in realistic low-symmetry metallocenes and idealized high-symmetry geometries. The results put to question the common view of the metal–ligand bonding in lanthanide complexes as completely or almost completely of ionic character, and have implications in the design of crystal-fields in lanthanide complexes when targeting specific magnetic properties. [ABSTRACT FROM AUTHOR]

Diene and cyclopentadienyl rhodium halides are very often used as catalysts for various transformations. Herein we analyze the advantages and limitations of classical and more recent synthetic methods for the preparation of these catalysts with a focus on the compounds with chiral ligands. [ABSTRACT FROM AUTHOR]

Resonance-stabilized cyclopentadienyl radicals are important intermediate species in the combustion of transportation fuels. It not only serves as precursors for polycyclic aromatic hydrocarbon (PAH) formation, but also involves in the formation of fundamental PAH precursors such as propargyl and acetylene. In this work, the unimolecular reactions of the cyclopentadienyl radicals are theoretically studied based on high-level quantum chemistry and RRKM/master equation calculations. Stationary points on the potential energy surface (PES) are calculated at the CCSD(T)/CBS//M06–2X/6–311++(d,p) level of theory. The branching ratios of unimolecular reactions of the cyclopentadienyl radicals are analyzed for a broad temperature range from 500 to 2500 K and pressures from 0.01 to 100 atm. It is found that the isomerization reaction of the cyclopentadienyl radical via 1,2-hydrogen transfer dominates at low temperatures and high pressures, while the well-skipping decomposition reaction which forms propargyl and acetylene is important at high temperatures and low pressures. Both the decomposition reaction of the cyclopentadienyl radicals and its reverse reaction show pronounced pressure dependence, and their reaction rate constants are compared against available low-pressure experimental measurements and theoretical studies. The temperature- and pressure-dependent rate coefficients for important reactions involved on the C 5 H 5 PES are calculated and updated in a chemical kinetic model. Impacts of the unimolecular reactions of the cyclopentadienyl radicals on the PAH formation are explored by the numerical modeling of a low-pressure cyclopentene counterflow diffusion flame. [ABSTRACT FROM AUTHOR]

Resonance-stabilized radical chain (RSRC) reactions were recently proposed as alternative formation and growth pathways of polycyclic aromatic hydrocarbons (PAHs). In the present study, the growth of indene from the resonance-stabilized cyclopentadienyl radical following a series of RSRC sequences is investigated. Temperature- and pressure-dependent rate coefficients for acetylene addition reactions to the cyclopentadienyl, vinylcyclopentadienyl, cycloheptatrienyl, and benzyl radicals are determined based on high-level quantum chemistry and RRKM/master equation calculations. The acetylene addition to the resonance-stabilized cyclopentadienyl radical can generate resonance-stabilized vinylcyclopentadienyl, cycloheptatrienyl, and benzyl radicals. The formation reaction of cycloheptatrienyl has the highest rate constant compared to those of vinylcyclopentadienyl and benzyl. The acetylene addition to the above three resonance-stabilized C 7 H 7 isomers forms indene. It is found that the indene formation reaction from C 2 H 2 addition to benzyl has the highest rate constant, while that from C 2 H 2 addition to cycloheptatrienyl is the lowest. The impacts of the investigated reactions on indene formation are then numerically explored in both counterflow diffusion and laminar premixed flame configurations. Results indicate that the RSRC pathways via C 2 H 2 addition to vinylcyclopentadienyl and cycloheptatrienyl radicals have marginal contributions to indene formation. [ABSTRACT FROM AUTHOR]

• Ruthenium cationic complexes derived from diazafluorenone derivative ligands. • CpRu(II) complexes showed better antimicrobial and anticancer activity. • Complex 1 showed the highest cytotoxicity towards DL cell line. We have successfully synthesized a series of eight versatile, half-sandwich ruthenium(II) cationic complexes [(Cp/Ind)Ru(к2 (N∩N) L)(PPh 3)]PF 6 (1–8), where L represents a 4,5-diazafluorenone derivative ligand. These complexes were isolated as their hexafluorophosphate salts and subjected to thorough characterization using various spectroscopic techniques such as FT-IR, NMR, UV and Mass. Furthermore, single-crystal X-ray diffraction studies determined the molecular structures of representative complexes 1, 7 , and 8. We screened the synthesized complexes and ligands in vitro to assess their potential antibacterial activity against three bacterial strains: the Gram-positive Staphylococcus aureus , the Gram-negative Escherichia coli and Klebsiella pneumoniae. Remarkably, all the compounds exhibited potent antibacterial activity against the tested organisms. In addition, we conducted a cell viability assessment to evaluate the cytotoxicity of the free ligands. The results indicated that the ligands did not demonstrate statistically significant cytotoxicity. However, it is noteworthy that complex 1 displayed more pronounced cytotoxic effects on the DL cell line, followed by complexes 3, 5 , and 7. [Display omitted] [ABSTRACT FROM AUTHOR]

• Organometallic technetium complexes are water-stable and appropriate for bioorganometallics. • Low pressure carbonylation gives access to any class of organometallic compounds of Tc. • Tc-99 and Tc-99 m chemistry often runs "differently" due to kinetic dominance for the latter. • Side-on alkene and alkyne complexes of technetium await discovery. • Technetium and rhenium chemistry are different, distinctly in the high - but less in the low oxidation states. This account briefly summarizes the organometallic chemistry of technetium over the thirty years of experience made by the author and others. Earlier publications, many from the " Journal of Organometallic Chemistry ", are included as well for showing that a careful reading of the "old" literature may influence actual chemistry, challenges and concepts, and the author's own research in particular. It is shown that kinetic differences between 99Tc and 99mTc lead to complexes not immediately envisaged under specific reaction conditions, but very useful for ultimate application in molecular imaging and bioorganometallic chemistry. As with many other d-elements, most of the organometallic chemistry is based on a few starting materials, e.g. binary carbonyls such as Tc 2 (CO) 10 , which is hardly available nowadays for different reasons. Still, there are ways around it to get to the same compounds as when starting from Tc 2 (CO) 10. Organometallic technetium chemistry, a niche field, is still underdeveloped which is mirrored by the fact that some important core organometallics such as η2-alkene and η2-alkyne complexes, standard for other d-elements, are still missing. [Display omitted] [ABSTRACT FROM AUTHOR]

The reactivity of the yttrium trichloride complex [Cl 3 Y{(μ 3 -NH) 3 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)}] (2) with a variety of main-group metal cyclopentadienyl reagents [M(C 5 H 3 R1R2)] (M = Li, Na, K, Tl) or [Mg(C 5 H 5) 2 ] has been investigated. Treatment of 2 with one equivalent of [Na(C 5 H 5)] or [K(C 5 H 4 SiMe 3)] gives the monocyclopentadienyl derivatives [(η5-C 5 H 4 R)Cl 2 Y{(μ 3 -NH) 3 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)}] (R = H (3), SiMe 3 (4)). Analogous reaction of 2 with lithium [Li(C 5 H 3 R1R2)] or thallium [Tl(C 5 H 5)] reagents (1 or 2 equivalents) leads to complexes [(η5-C 5 H 3 R1R2) 2 Y(μ-Cl) 2 M{(μ 3 -NH) 3 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)}] (M = Li, R1 = R2 = H (5), R1 = H, R2 = SiMe 3 (6), R1 = R2 = SiMe 3 (7); M = Tl, R1 = R2 = H (8)). Complex 2 reacts with [Mg(C 5 H 5) 2 ] to yield the ionic compound [(μ-Cl) 3 Mg 2 {(μ 3 -NH) 3 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)} 2 ][{Y(η5-C 5 H 5) 2 Cl} 2 (μ-Cl)] (9). In contrast to the metathesis of chloride ligands, the reaction of 2 with the lithium indenyl derivative [Li(C 9 H 7)] at room temperature produces C 9 H 8 and the precipitation of [Li(μ-Cl) 3 Y{(μ 3 -N)(μ 3 -NH) 2 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)}] (10). Crystallization of 10 in pyridine affords the lithium-free [Cl 2 (py) 2 Y{(μ 3 -N)(μ 3 -NH) 2 Ti 3 (η5-C 5 Me 5) 3 (μ 3 -N)}] (11) complex. The X-ray crystal structures of 6 and 11 have been determined. Image 1 • Yttrium complexes with a tridentate imido-nitrido titanium metalloligand were synthesized. • Cyclopentadienyl derivatives were prepared by salt metathesis of chloride ligands bonded to yttrium. • Bis(cyclopentadienyl)magnesium gave a compound with a double-cube titanium-magnesium cation. • Indenyllithium led to deprotonation of a NH imido group and formation of a bridging nitrido ligand. [ABSTRACT FROM AUTHOR]

Highlights • The synthesis of [Ni(Cp)(X)(NHC)] and [Ni(Cp)(L)(NHC)]+ are summarized. • The stoichiometric reactions employing [Ni(Cp)(X)(NHC)] are presented. • The solid state structure of [Ni(Cp)(X)(NHC)] and [Ni(Cp)(L)(NHC)]+ is discussed. • Catalytic applications of [Ni(Cp)(X)(NHC)] and [Ni(Cp)(L)(NHC)]+ are also reviewed. Abstract Complexes [Ni(Cp)(X)(NHC)] and their ionic derivatives [Ni(Cp)(L)(NHC)]+ have attracted significant interest in recent years owing to their simple preparation, stability in the solid state, and versatile reactivity in both stoichiometric and catalytic reactions. In this review, the syntheses of the title complexes are comprehensively presented with respect to the scope of each ligand. The stoichiometric reactions involving [Ni(Cp)(X)(NHC)] as substrates, providing access to novel organometallics or inorganics, are also presented. Detailed discussion of the solid state structures of [Ni(Cp)(X)(NHC)] and [Ni(Cp)(L)(NHC)]+ based on the data deposited in Cambridge Structural Database is presented. It is shown on this basis that Ni2+ should be treated as four-coordinate with square planar coordination polyhedron. The second part of this review deals with the reported to date catalytic applications of [Ni(Cp)(X)(NHC)] in numerous reactions, such as Suzuki-Miyaura cross-coupling, Kumada-Tamao-Corriu cross-coupling, arylamination reactions, or polymerizations of olefins. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Trans-disubstituted diamido diamine cyclams support cationic zirconium complexes. • (Bn 2 Cyclam)ZrCl 2 reacts with silver salts to form either neutral or cationic species. • (Bn 2 Cyclam)Zr(C 6 F 5) 2 displays a fluxional behaviour in solution. • (Bn 2 Cyclam)ZrCl} 2 (k 2- N,N' -Bn 2 Cyclam) displays one terminal- and one bridging- cyclam. • [(ansa -η5:η5-Cp 2 CMe 2)ZrCl(HBn 2 Cyclam)] is the first mixed cyclam/cyclopentadienyl complex. Abstract (Bn 2 Cyclam)ZrCl 2 reacts with silver salts to form either neutral or cationic species depending on the nature of the counterion. The reaction of (Bn 2 Cyclam)ZrCl 2 with AgCF 3 COO affords (Bn 2 Cyclam)Zr(OCOCF 3) 2 while with AgPF 6 the cationic species [(Bn 2 Cyclam)ZrCl(CH 3 CN)]PF 6 is formed. Cations of formulas [(All 2 Cyclam)ZrX(L)]+ (X = Me, L = CD 2 Cl 2 ; X, L = η2-CH 2 Ph), [(MeAll 2 Cyclam)Zr(η2-CH 2 Ph)]+ and [(Bn 2 Cyclam)Zr(n Bu)(THF)]+ were prepared by abstraction of one alkyl ligand from (R 2 Cyclam)ZrX 2 (R = All, MeAll, Bn; X = Me, CH 2 Ph, n Bu) using B(C 6 F 5) 3 or [PhMe 2 NH][B(C 6 F 5) 4 ]. (Bn 2 Cyclam)Zr(C 6 F 5) 2 was obtained by reaction of (Bn 2 Cyclam)ZrCl 2 with 2 equiv. of MgBrC 6 F 5. The complex (Bn 2 Cyclam)ZrCl} 2 (k 2- N,N' -Bn 2 Cyclam) displaying a cyclam bridging ligand was obtained either from the 1:1 reaction of (Bn 2 Cyclam)ZrCl 2 with LiNiPr 2 and from the reaction of 2 equiv. of (Bn 2 Cyclam)ZrCl 2 with Li 2 (Bn 2 Cyclam).(THF) 2 in THF. The reaction of LiCpC(Me) 2 CpLi with (Bn 2 Cyclam)ZrCl 2 led to the formation of the mixed cyclam/cyclopentadienyl complex [(ansa -η5:η5-Cp 2 CMe 2)ZrCl(HBn 2 Cyclam)]. [ABSTRACT FROM AUTHOR]

Graphical abstract The first transition-metal η 5-tetramethyl(diphenylmethyl)cyclopentadienyl complex is prepared from [(η 5-C 5 Me 4 CF 3)Fe(CO) 2 Br] by a triple Lewis acid-mediated carbon–fluorine bond activation consisting of two defluorinative arylations and a hydrodefluorination. The work exposes an Achilles' Heel for the η 5-[(trifluoromethyl)tetramethylcyclopentadienyl)] (Cp∗CF3) ligand. Abstract The η 5-(trifluoromethyl)tetramethylcyclopentadienyl iron complex, [(η 5-C 5 Me 4 CF 3)Fe(CO) 2 Br] (2 - Cp∗CF3), undergoes reaction with benzene in the presence of AlCl 3 to give the first transition-metal η 5-tetramethyl(diphenylmethyl)cyclopentadienyl complex, [(η 5-C 5 Me 4 CHPh 2)Fe(CO) 3 ]PF 6 (3 - Cp∗CHPh2). This mechanistically complex, one-pot conversion involves a triple Lewis acid-mediated carbon–fluorine bond activation, including two defluorinative arylations and a hydrodefluorination. The structures of 2 - Cp∗CF3 and 3 - Cp∗CHPh2 are determined by X-ray crystallography and computation. This work exposes an Achilles' Heel for the η 5-[(trifluoromethyl)tetramethylcyclopentadienyl)] (Cp∗CF3) ligand. [ABSTRACT FROM AUTHOR]

Abstract The reaction of the nitrosyl complex [CpMo(CO) 2 (NO)] (Cp = η-C 5 H 5) with the nickel dithiolene complex [Ni(S 2 C 2 Ph 2) 2 ] produces the expected dimolybdenum complex [Mo 2 (NO) 2 (μ-S 2 C 2 Ph 2) 2 Cp 2 ], but only as a minor product (13% yield). The major product (41%) consists of two separable isomers of the tetranuclear complex [Mo 2 Ni 2 (NO) 2 (μ-S 2 C 2 Ph 2) 4 Cp 2 ], which comprises two CpMo(NO)Ni(S 2 C 2 Ph 2) 2 units joined through bridging sulfur atoms. The isomers differ in the orientation of one dimeric unit in relation to the other. All three compounds have been structurally characterised. Graphical abstract The nitrosyl complex [CpMo(CO) 2 (NO)] (Cp = η-C 5 H 5) reacts with the nickel dithiolene complex [Ni(S 2 C 2 Ph 2) 2 ] to give the expected dimolybdenum complex [Mo 2 (NO) 2 (μ-S 2 C 2 Ph 2) 2 Cp 2 ], but the major product consists of two separable isomers of the tetranuclear complex [Mo 2 Ni 2 (NO) 2 (μ-S 2 C 2 Ph 2) 4 Cp 2 ], which comprises two CpMo(NO)Ni(S 2 C 2 Ph 2) 2 units joined through bridging sulfur atoms. Image 1 Highlights • Dithiolene transfer reactions can provide useful routes to new dithiolene complexes. • The complex [Mo 2 (NO) 2 (μ-S 2 C 2 Ph 2) 2 Cp 2 ] is formed from [CpMo(CO) 2 NO] and [Ni(S 2 C 2 Ph 2) 2 ]. • Two isomers of [Mo 2 Ni 2 (NO) 2 (μ-S 2 C 2 Ph 2) 4 Cp 2 ] are also produced. • All three products have been crystallographically characterised. [ABSTRACT FROM AUTHOR]

Efforts to generate Ln 2+ precursors suitable for reduction to Ln 1+ compounds have provided the X-ray crystal structures of Cp″ 2 Sm, 1-Sm , and Cp tt 2 Ln, 2-Ln [Ln = Eu, Sm; Cp″ = C 5 H 3 (SiMe 3 ) 2 ; Cp tt = C 5 H 3 (CMe 3 ) 2 ], allowing direct comparisons of these similar cyclopentadienyl rings in Ln 2+ complexes. In the solid state, these complexes exhibit extensive intermolecular interactions. Bridging cyclopentadienyl ligands are found with both types of ligands and the Cp″ ligand engages in silyl-methyl-metal interactions. The compounds display bent metallocene structures with (ring centroid)–Ln–(ring centroid) angles ranging from 110.0° to 147.9°. Complex 2-Eu reacts with [HNEt 3 ][BPh 4 ] to form the mono(cyclopentadienyl) tetraphenylborate complex, ( η 5 -Cp tt )Eu( μ-η 6 : η 1 -Ph) 2 BPh 2 , 3-Eu , in which the Eu 2+ ion is coordinated by three carbocyclic ligands in a nearly trigonal planar geometry. [ABSTRACT FROM AUTHOR]

This work describes a procedure giving cyclopentadienyl molybdenum(II) compounds bearing carboxylic acid function group. It involves synthesis of carboxylic acid ester functionalized cyclopentadienides, their coordination to molybdenum(II) precursor and saponification of ester function groups. The method is not limited only to compounds with the function group directly attached in the cyclopentadienyl ring but also to those functionalized in the side chain. The attempts to synthesize the indenyl analogues were only partially successful due to low stability in the saponification step. All reported structure types were elucidated from spectroscopic measurements and verified by X-ray crystallography. The second part of the work describes an effect of the outer-coordination sphere on cytotoxicity of the cationic molybdenum(II) compounds bearing N,N -chelating ligands. The cytotoxicity of the modified species bearing phenanthroline ligand toward human leukemia cells MOLT-4 (IC 50  = 10.5 ± 0.5 μmol l −1 ) is higher than reported for cisplatin (IC 50  = 15.8 ± 1.9 μmol l −1 ). [ABSTRACT FROM AUTHOR]

The potential energy surface for the reaction of cyclopentadienyl radical with O 2 has been studied using ab initio calculations at the CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6-311G(d,p) level and the RRKM-Master Equation approach has been employed to compute reaction rate constants and product branching ratios at various temperatures and pressures pertinent to combustion. The results show that at low temperatures from 500 to 800–1250 K (depending on pressure), the reaction predominantly forms a collisionally-stabilized C 5 H 5 OO complex and then, the thermalized complex rapidly decomposes back to the reactants establishing a C 5 H 5  + O 2 /C 5 H 5 OO equilibrium. At higher temperatures, typically above 1000 K, the mechanism is different and the C 5 H 5  + O 2 reaction proceeds to form various bimolecular products. Cyclopentadienone C 5 H 4 O + OH are predicted to be the predominant product (63.5–83.3%). Relatively minor products include H 2 CCHCHC(H)O + CO (20-3%), vinylketene + HCO (12-2%), and OC(H)CHCHCHCO + H (3-5%), which are formed via the OC(H)CHCHCHC(H)O intermediate residing in a deep potential well, and highly endothermic C 5 H 5 O + O (up to 6.5% at 2500 K) produced directly by the O O bond cleavage in the initial complex. The calculated rate constants for the formation of C 5 H 4 O + OH and C 5 H 5 O + O are shown to be independent of pressure above 800 K, but the rate constants for the reaction channels resulting in CO, HCO, and H eliminations show some pressure dependence in the low end of the high-temperature regime and decrease with the pressure growing from 10 to 100 atm. The CO 2 loss channel leading to the formation of 1,3-butadien-1-yl C 4 H 5 is shown to be negligible. The total reaction rate constants at all considered pressures from 0.03 to 100 atm merge at 1375 K and show no pressure dependence at higher temperatures, as only the bimolecular products are formed. Overall, the rate constant of the C 5 H 5  + O 2 reaction at combustion-relevant temperatures is predicted to be very slow, 10 −16 -10 −15 cm 3 molecule −1 s −1 , that is typically ∼5 orders of magnitude lower than those for the oxidation reactions of cyclopentadienyl with OH and O( 3 P). A comparison of the rates of the C 5 H 5  + O 2 /OH/O reactions allowed us to conclude that molecular oxygen can play only a small role in oxidation and removal of five-member rings in combustion and only when the concentration of O 2 is orders of magnitude higher than the concentrations of O and OH. [ABSTRACT FROM AUTHOR]

The electrochemistry of nine Ni(II) N-heterocyclic carbene (NHC) complexes of general formula [CpNiBr(NHC)], bearing either a symmetric or asymmetric N -substituted alkyl/benzyl/phenethyl NHC ligand with Cp = cyclopentadienyl is described. Both metal and ligand-centred redox processes have been observed and systematically evaluated. The reversible to quasi-reversible Ni II /Ni III couple (0.062 V ≤  E 0 ′ ≤ 0.127 V) is followed by the electrochemically and chemically irreversible ligand based oxidation peaks ( E pa  ~ 0.37 V and ~0.5 V). The Ni II /Ni I and NHC ligand reduction processes were observed below −1.3 V. A comparison between the nine different Ni(II)-NHC complexes revealed that the electron-withdrawing NO 2 -containing NHC ligands exhibit the most positive metal-oxidation redox processes. A DFT study complements the experimental findings by establishing where the oxidation and reduction centres were based. [ABSTRACT FROM AUTHOR]

Treatment of the tris(cyclopentadienyl) thorium(III) complex [Th(η 5 -Cp′′) 3 ] [ 1 , Cp′′ = C 5 H 3 -1,3-(SiMe 3 ) 2 ] with the N -heterocyclic olefin H 2 C=C(NMeCH) 2 ( 2 ) reproducibly produces the thorium(IV)-methyl derivative [Th(η 5 -Cp′′) 3 (Me)] ( 3 ) along with MeImCH 2 CH 2 ImMe (Im = imidazole). The reaction mechanism, which is consistent with 1 H NMR spectroscopic observations, is proposed to proceed via: (i) coordination of 2 to 1 ; (ii) one-electron transfer from thorium to 2 ; (iii) N -methyl cleavage and transfer to thorium to give 3 ; (iv) coupling of the resulting imidazolium radical by-product to give MeImCH 2 CH 2 ImMe. Complex 3 has been characterised by single crystal X-ray diffraction, multi-nuclear NMR and IR spectroscopies, and elemental analyses, and MeImCH 2 CH 2 ImMe by 1 H NMR spectroscopy and mass spectrometry. [ABSTRACT FROM AUTHOR]

The equimolar reaction of [(C 5 Me 5 )LnMe 2 ] 3 (Ln = Y, Lu) with (DippForm)AlMe 2 gave the ligand-rearranged complexes (C 5 Me 5 )Ln(AlMe 4 )(DippForm) in quantitative yields. The half-sandwich complexes were fully characterized including X-ray structure analyses. Donor solvent (THF)-induced alkylaluminate cleavage of (C 5 Me 5 )Lu(AlMe 4 )(DippForm) gave complex [(C 5 Me 5 )LuMe(DippForm)(thf)] exclusively, as evidenced by 1 H‒ 13 C HSQC NMR spectroscopy. Treatment of polymeric [LuMe 3 ] n with formamidine DippFormH produced a mixture of two compounds, namely, the bis(formamidinate) complex (DippForm) 2 LuMe and the methyl methylidene complex [{(DippForm)Lu( μ 2 -Me)} 3 ( μ 3 -Me)( μ 3 -CH 2 )]. While monomeric (DippForm) 2 LuMe revealed a very short Lu–C terminal methyl bond lengths of 2.314(3) Å in the solid state, the structure of the trimetallic methylidene complex could be assigned unambiguously on the basis of a 1 H‒ 13 C HSQC NMR spectrum. Preliminary studies on the performance of complex (C 5 Me 5 )Y(AlMe 4 )(DippForm) in isoprene polymerization revealed that upon activation with borate co-catalysts [Ph 3 C][B(C 6 F 5 ) 4 ] and [PhNMe 2 H][B(C 6 F 5 ) 4 ] highly active catalyst systems are obtained, producing polyisoprenes with dominant 3,4-units (57% and 58%). [ABSTRACT FROM AUTHOR]

The lanthanide borohydrides [Ln(BH 4 ) 3 (THF) n ] [Ln = La, n = 4 ( 1 ); Ln = Ce, n = 3.5] were treated with the substituted cyclopentadienyl potassium transfer agents KCp tt (Cp tt = C 5 H 3 t Bu 2 -1,3), KCp ttt (Cp ttt = C 5 H 2 t Bu 3 -1,2,4) and KCp′′′ (Cp ′′′ = C 5 H 2 (SiMe 3 ) 3 -1,2,4) in various reaction conditions to yield the heteroleptic lanthanide complexes [La(Cp tt ) 2 (μ-BH 4 )] 2 ( 2 ), [La(Cp ttt )(BH 4 ) 2 (THF) 2 ] ( 3 ), [La(Cp ttt )(μ-BH 4 ) 2 ] 6 ( 4 ), [Ce(Cp ttt )(BH 4 )(μ-BH 4 )(THF)] 2 ( 5 ), [La(Cp ttt ) 2 (BH 4 )] ( 6 ) and [Ln(Cp) 2 (BH 4 )(THF)] (Ln = La, 7 ; Ce, 8 ) by salt metathesis protocols. Complexes 1–8 have been variously characterized by single crystal X-ray diffraction, multi-nuclear NMR and FTIR spectroscopies, and elemental analyses. [ABSTRACT FROM AUTHOR]

Potential energy surfaces for the C 5 H 5 + OH and C 15 H 9 + OH reactions have been studied by ab initio calculations at the CCSD(T)-F12/cc-pVTZ-f12//B3LYP/6-311G(d,p) and G3(MP2,CC)//B3LYP/6-311G(d,p) levels of theory, respectively, in order to unravel the mechanism of oxidation of the cyclopentadienyl radical and five-member-ring radicals embedded in a sheet of six-member rings with OH. The VRC-TST approach has been employed to compute high-pressure-limit rate constants for barrierless entrance and exit reaction steps and multichannel/multiwell RRKM-ME calculations have been utilized to produce phenomenological pressure- and temperature-dependent absolute and individual-channel reaction rate constants. The calculations allowed us to quantify relative yields of various products in a broad range of conditions relevant to combustion and to generate rate expressions applicable for kinetic models of oxidation of aromatics. The C 5 H 5 + OH reaction is shown to proceed either by well-skipping pathways without stabilization of C 5 H 6 O intermediates leading to the bimolecular products ortho -C 5 H 5 O + H, C 5 H 4 OH (hydroxycyclopentadienyl) + H, and C 4 H 6 (1,3-butadiene) + CO, or via stabilization of the C 5 H 6 O intermediates, which then undergo unimolecular thermal decomposition to ortho -C 5 H 5 O + H and C 4 H 6 + CO. The well-skipping and stabilization/dissociation pathways compete depending on the reaction conditions; higher pressures favor the stabilization/dissociation and higher temperature favor the well-skipping channels. For the C 15 H 9 + OH reactions, the results demonstrate that embedding decreases the oxidation rate constants and hinder the decarbonylation process; the removal of CO grows less likely as the number of common edges of the five-member ring with the surrounding six-member rings increases. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, mutagenic and/or carcinogenic to humans. To reduce the emission of PAHs, it's significant and indispensable to explore the PAH formation mechanism. In the present work, the growth mechanism of PAHs from the reactions of anthracene and phenanthrene with cyclopentadienyl and indenyl radicals was investigated with the aid of high-accuracy quantum chemistry calculation. The rate constants of key elementary steps were calculated by meaning of the canonical variation transition-state (CVT) theory with the small curvature tunneling (SCT) correction over the temperature range of 400–1400 K. The mechanism of the PAH formation involves in six elementary steps, addition reaction, ring closure, intramolecular H-shift, cleavage of C C bond, intramolecular H-shift and unimolecular elimination of CH 3 or H. The cleavage of C C bond is the rate-determining step due to the high barrier. The formation of PAHs from the reactions of anthracene with cyclopentadienyl and indenyl radicals is easier than that from the reactions of phenanthrene. [ABSTRACT FROM AUTHOR]

The reductive chemistry of [Cp' 2 Ln( μ– H)(THF) x ] y [Ln = Y, Dy, Tb; Cp' = (C 5 H 4 SiMe 3 ) 1− ; x = 2, 0 and y = 2, 3] was examined to determine if these hydrides would be viable precursors for 4f n 5d 1 Ln 2+ ions that could form 5d 1 -5d 1 metal–metal bonded complexes. The hydrides were prepared by reaction of the chlorides, [Cp' 2 Ln( μ –Cl)] 2 , 1-Ln , with allylmagnesium chloride to form the allyl complexes, [Cp' 2 Y( η 3 –C 3 H 5 )(THF)], 2-Ln , which were hydrogenolyzed. The solvent-free reaction of solid 2-Ln with 60 psi of H 2 gas in a Fischer-Porter apparatus produced, in the Y case, the trimetallic species, [Cp' 2 Y( μ –H)] 3 , 3-Y , and in the Dy and Tb cases, the bimetallic complexes [Cp' 2 Ln( μ –H)(THF)] 2 , 4-Ln (Ln = Dy, Tb). The latter complexes could be converted to 3-Dy and 3-Tb by heating under vacuum. Isopiestic data indicate that 3-Y solvates to 4-Y in THF. Reductions of 4-Y , 4-Dy , and 4-Tb with KC 8 in the presence of a chelate such as 2.2.2-cryptand or 18-crown-6 all gave reaction products with intense dark colors characteristic of Ln 2+ ions. In the yttrium case, with either chelating agent, the dark green product gives a rhombic EPR spectrum (g 1 = 2.01, g 2 = 1.99, g 3 = 1.98, A = 24.1 G) at 77 K. However, the only crystallographically-characterizable products obtainable from these solutions were Ln 3+ polyhydride anion complexes of composition, [K(chelate)]{[Cp' 2 Ln( μ– H)] 3 ( μ– H)}. Reduction of 1-Y with KC 8 in the presence of 2.2.2-cryptand also yields an intensely colored product with an axial EPR spectrum (g x = g y = 2.05, A x = A y = 35.5 G; g z = 2.07, A z = 34.5) similar to that of (Cp' 3 Y) 1− ion, but crystals were not obtained from this system. [ABSTRACT FROM AUTHOR]

Ab initio calculations of potential energy surfaces in conjunction with the RRKM-Master Equation theoretical approach have been employed to evaluate temperature- and pressure-dependent total and product specific rate constants and product branching ratios for unimolecular thermal decomposition of 2,4-cyclopentadienone C 5 H 4 O and for the C 5 H 4 O + H and C 5 H 5 + O reactions. The formation of the cyclobutadiene + CO products via a ring contraction/CO elimination mechanism is shown to be the prevailing channel for the unimolecular decomposition of C 5 H 4 O. The unimolecular reaction is found to be relatively slow, but decomposition of cyclopentadienone can be greatly facilitated through bimolecular encounters with H atoms. The C 5 H 4 O + H reaction is predicted to be fast, with rate constants ranging from 4.6 × 10 −12 to 1.8 × 10 −10 cm 3 molecule −1 s −1 at T = 500–2500 K and finite pressures. Cyclic C 5 H 5 O intermediates formed after the initial H addition undergo ring openings by β -scissions and then decompose to either butadienyl C 4 H 5 + CO or 1-oxoprop-2-enyl H 2 CCHCO + C 2 H 2 , which are respectively predicted as the major and the minor reaction products. The calculations predict that thermal decomposition of the ortho and meta C 5 H 5 O radicals as well as pyranyl nearly exclusively forms the C 4 H 5 + CO products, whereas decomposition of hydroxycyclopentadienyl C 5 H 4 OH predominantly produces cyclopentadienone + H. The C 5 H 5 + O reaction is shown to proceed by barrierless oxygen addition to the ring followed by fast H migration, ring opening, and dissociation to C 4 H 5 + CO. The C 5 H 5 + O rate constant is calculated to be close to 1 × 10 −10 cm 3 molecule −1 s −1 and to be pressure-independent and nearly independent of temperature. Modified Arrhenius expressions for rate constants for all considered reactions at the high-pressure limit and at finite pressures are generated for kinetic modeling. [ABSTRACT FROM AUTHOR]

Treatment of the N -heterocyclic chlorophosphine precursor (PPP)Cl ( 1 ) with two equivalents of nickelocene (NiCp 2 ) affords the phosphorus-bridged dimer [(μ-PPP)Ni 2 Cp 2 ]Cl ( 2 ). In contrast, an equimolar mixture of 1 and NiCp 2 in the presence of PPh 3 generates a different product, (PP(C 5 H 5 )P)NiCl 2 ( 3 ), in which a cyclopentadienyl anion has migrated to the N -heterocyclic phosphenium center. The phosphorus-bound Cp ring in complex 3 has undergone a [1,5]-hydride shift to afford a vinylic C 5 H 5 − ring, and can be subsequently deprotonated to produce [(PP(C 5 H 4 )P)NiCl] ( 4 ). [ABSTRACT FROM AUTHOR]

[Display omitted] • Five novel compounds L 1 , L 4 , L 5 , L 9 and L 10 were synthesized via arylation of ferrocene by diazonium salt under phase transfer condition. • The cyclic voltammograms of compounds L 1 , L 4 , L 5 , L 9 and L 10 showed a clear well-defined redox peak in both conditions. • The calibration plots confirmed that L 1 , L 4, L 5 , L 9 , and L 10 showed reversible electron transfer processes and diffusion control processes. • The LUMO energy levels give better electrons transportation compare to the LUMO energy level of the conduction band edge of TiO 2. Five derivatives of 3-ferrocenylphenylimine were synthesized through arylation of ferrocene by diazonium salt under phase transfer conditions. Sn/HCl was used to reduce the nitro derivatives to ferrocenylanilines, which was followed by addition of aromatic aldehydes. The thus obtained compounds N-(2,3-dimethoxybenzylidene)-3-ferrocenylimine (L 1), N-(4-nitrobenzylidene)-3-ferrocenylimine (L 4), N-(2-thiophenecarboxbenzylidene)-3-ferrocenylimine (L 5), N-(3-nitrobenzylidene)-3-ferrocenylimine (L 9), and N-(2-furabenzylidene)-3-ferrocenylimine (L 10) showed similar UV–vis absorption spectra with the exception of L 4 which is the nitro-substituted benzylideneimine. Cyclic voltammetry of peak potential separation of the compounds under light and dark conditions was studied and the redox couple ferrocene/ferrocenium showed half-wave potentials around 0.05 V vs Ag/AgCl which is markedly higher than ferrocene. The dependence of the peak potentials and currents from the scan rates was studied in detail. While the energy of the highest occupied molecular orbital was obtained from the half-wave potential of the oxidation, the energy of the lowest unoccupied molecular orbital (LUMO) was estimated from the onset of the absorption spectra. The gaps range from 2.87 to 3.05 eV. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are globally concerned atmospheric particle-bound pollutants due to their toxicities. A mechanistic understanding of their formation from other environmental sources is of crucial importance for successful prevention of PAH. In the present work, the formation and growth mechanism of PAHs from the reactions of naphthalene with the cyclopentadienyl and indenyl radicals was investigated by using the hybrid density functional theory (DFT) at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. The rate constants for the crucial elementary steps were deduced with the aid of the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution. The formation of PAHs was involved in six elementary processes including: the addition reaction, ring closure, intramolecular H-shift, C-C cleavage, intramolecular H-shift and unimolecular elimination of CH 3 or H. The C-C cleavage steps were revealed as the rate determining steps due to the extremely high barrier. At high temperature conditions like the combustion and pyrolysis of many hydrocarbons, the main products are phenanthrene, 4-methyl-phenanthrene and 1-methyl-phenanthrene from the reactions of naphthalene and cyclopentadienyl, and benzo( a )anthracene, 12-methyl-phenanthrene and 7-methyl-phenanthrene from the reactions of naphthalene and indenyl radicals. The reaction of naphthalene with indenyl radical is slightly more difficult than the reaction of naphthalene with cyclopentadienyl radical because of the bigger HOMO-LUMO orbital energy difference of naphthalene with indenyl relative to that of naphthalene with cyclopentadienyl. [ABSTRACT FROM AUTHOR]

• Complexes were isolated as bidentate cationic complexes with Cl/PF 6 ˉ as the counter ion. • Ligands and all complexes show potent antioxidant activity except complex 4. • Among the tested compounds complex 7 showed highest antibacterial activity. A series of cationic complexes [(Cp/Ind)Ru(к2 (NS) -L)(PPh 3)]PF 6 (1–8) were synthesized by the reaction of [CpRu(PPh 3) 2 Cl] or [(Ind)Ru(PPh 3) 2 Cl] (Cp=η5-C 5 H 5 , Ind=η5-C 9 H 7) with respective pyridyl/pyrimidyl thiourea derivatives 1-phenyl-3-(pyridin-2-yl)thiourea (L1), 1-phenyl-3-(pyrazin-2-yl)thiourea (L2), 1-(4-methylpyridin-2-yl)-3-phenylthiourea (L3) and 1-benzyl-3-(pyridin-2-yl)thiourea (L4). The complexes have been fully characterized by IR, UV–Vis, NMR and ESI-MS spectral methods. The molecular structures of complexes 1 and 3 were established by single-crystal X-ray diffraction studies. Furthermore, the complexes (1–8) and the ligands were screened for radical scavenging activity and pathogenic bacteria such as S. aureus, E. coli and K. pneumoniae. [Display omitted] Cyclopentadienyl and indenyl Ru(II) cationic complexes (1–8) containing chelating N∩S pyridyl/pyrimidyl based thiourea derivative ligands were synthesized and their biological activity were investigated. Graphical Abstract (pictogram) [ABSTRACT FROM AUTHOR]

The structure of Fe(C 5 Me 5 )(2,4-C 7 H 11 ) has been determined (C 7 H 11 = dimethylpentadienyl), and found to be isomorphous with its ruthenium analogue. The Fe–C bond distances for the open pentadienyl ligand have been found to be about 0.02 Å shorter than those for the aromatic pentamethylcyclopentadienyl ligand, whereas for the simple cyclopentadienyl analogue, the Fe–C bond distances for the two ligand types were nearly identical. While the structural data support proposals that the pentadienyl ligand is more strongly bound, the complex reacts readily with silica aerogel, during which it is the nonaromatic pentadienyl ligand which is removed via protonation. Solid state 13 C NMR spectra are consistent with incorporation of the metal into one major environment, with lesser degrees of incorporation into alternative environments. [ABSTRACT FROM AUTHOR]

This article outlines the synthesis of an electrophilic organoruthenium carboxylic acid of the structure [(η 5 -Cp*)Ru(η 6 -C 6 H 5 CO 2 H)] + and explores the behavior of this molecule under a variety of nucleophilic substitution conditions using a range of oxygen and nitrogen based nucleophiles including alcohols, primary and secondary amines and aromatic sulfonamides. The resulting organoruthenium ester [(η 5 -Cp*)Ru(η 6 -C 6 H 5 COOR)] + and amide [(η 5 -Cp*)Ru(η 6 -C 6 H 5 CONHR)] + or [(η 5 -Cp*)Ru(η 6 -C 6 H 5 CONR)] + complexes are additionally reported. All prepared complexes have been fully characterized using Fourier-transform IR and NMR spectroscopy and electrospray mass spectrometry with single-crystal X-ray structural determinations reported for three complexes: 3[(η 5 -Cp*)Ru(η 6 -C 6 H 5 CO 2 H)]B(C 6 H 5 ) 4 .[(η 5 -Cp*)Ru(η 6 -C 6 H 5 CO 2 )].H 2 O, [(η 5 -Cp*)Ru(η 6 -C 6 H 5 CONHCH 2 Ph)]PF 6 and [(η 5 -Cp*)Ru(η 6 -C 6 H 5 CONHSO 2 C 6 H 4 COMe)]PF 6 . Complexes were also evaluated for in vitro cytotoxic activity against the MCF7 (hormone-dependant breast cancer), MDA-MD-231 (hormone-independent breast cancer), MM96L (human melanoma) tumourigenic cell lines and the normal NFF (neonatal foreskin fibroblasts) human cell line. [ABSTRACT FROM AUTHOR]

Reactions of Cp 2 TiMe 2 , with the ester derivatives of organometallic sandwich compounds (ɳ 5 -RC 5 H 4 )Fe(ɳ 5 -C 5 H 5 ) and (ɳ 5 -RC 5 H 4 )Co(ɳ 4 -C 4 Ph 4 ) (R=ester groups) gave products having R=C(CH 2 )Me, instead of the expected vinyl ethers indicating conversion of the ester units by Cp 2 TiMe 2 to methyl ketones followed by methylenation. A reaction of Cp 2 TiMe 2 with the diester (ɳ 5 -RC 5 H 4 )Co(ɳ 4 -C 4 Ph 3 R)(R C(O)OMe) also gave similar results. The study has also been successfully extended to metal sandwich derived amides, thio and seleno esters. By controlling the amount of Cp 2 TiMe 2 , the reactions were also stopped at the methyl ketone stage and the methyl ketones were isolated in good yields and characterized. The method provides an easy and direct access to convert organometallic sandwich derived esters and related compounds to 1-methylvinyl derived products. [ABSTRACT FROM AUTHOR]

Tetrahedral Mo 2 Ir 2 (μ 3 -CO)(μ-CO) 5 (CO) 4 ( η 5 -C 5 H 5 ) 2 ( 1 ) reacted with P(C 6 H 4 Me-4) 3 , P(C 6 H 2 Me 2 -3,5-OMe-4) 3 , and AsPh 3 to afford the substitution products Mo 2 Ir 2 (μ-CO) 3 (CO) 6 (L)( η 5 -C 5 H 5 ) 2 [L = P(C 6 H 4 Me-4) 3 ( 3 ), P(C 6 H 2 Me 2 -3,5-OMe-4) 3 ( 4 ), AsPh 3 ( 5 )] in fair to good yields, while reaction of 1 with HC≡CSiPr i 3 proceeded by insertion into the Mo–Mo bond to give the pseudo-octahedral Mo 2 Ir 2 (μ 4 - η 2 -HC 2 SiPr i 3 )(μ-CO) 4 (CO) 4 ( η 5 -C 5 H 5 ) 2 ( 6 ) in fair yield. While MoIr 3 (μ-CO) 3 (CO) 7 ( η 5 -C 5 H 5 ) reacted with HC≡CSiMe 3 to give a complex mixture of thus-far-uncharacterized products, its phosphine substitution product MoIr 3 (μ-CO) 3 (CO) 5 (PPh 3 ) 2 ( η 5 -C 5 H 5 ) reacted with the same alkyne via insertion into a Mo–Ir bond to afford the pseudo-octahedral MoIr 3 (μ 4 - η 2 -HC 2 SiMe 3 )(μ-CO) 3 (CO) 4 (PPh 3 ) 2 ( η 5 -C 5 H 5 ) ( 8 ) in good yield. Clusters 4 , 5 (two isomers), 6 and 8 have been characterized by single-crystal X-ray diffraction studies. Cyclic voltammetric studies of Mo 2 Ir 2 (μ-CO) 3 (CO) 6 (PPh 3 )( η 5 -C 5 H 5 ) 2 ( 2 ), 3 – 6 and 8 confirmed the tuning of redox potentials upon phosphines/arsine introduction and alkyne modification. IR spectroelectrochemical studies of 2 , 6 , and 8 suggest decreasing proclivity for bridging carbonyl ligands following oxidation. Variable temperature 31 P NMR studies of 3 and 4 revealed interconverting isomers in solution, the structures of which are assigned as analogues of the X-ray diffraction-confirmed isomers of 5 . Studies of 2 – 5 using ns pulses and the open-aperture Z-scan technique revealed that all are optical limiters at wavelengths in the visible region. [ABSTRACT FROM AUTHOR]

The coordination chemistry of MeCN, t BuCN, and PhCN with the cationic rare earth metallocene complexes [(C 5 Me 5 ) 2 Ln][( μ -Ph) 2 BPh 2 ], 1 - Ln (Ln = Y, La, Gd), has been examined to determine how nitrile coordination will affect the metallocene geometry. Crystallographic determination of geometry was possible for [(C 5 Me 5 ) 2 Ln(NCMe) 3 ][BPh 4 ] ( 2 - Y , 2 - Gd ), [(C 5 Me 5 ) 2 Y(NC t Bu) 3 ][BPh 4 ] ( 3 - Y ), and [(C 5 Me 5 ) 2 Ln(NCPh) 3 ][BPh 4 ] ( 4 - La , 4 - Gd ). In each case, only three nitriles are found to coordinate and the metallocenes are bent with (C 5 Me 5 ring centroid)–metal–(C 5 Me 5 ring centroid) angles of 137–140°. The THF adduct, [(C 5 Me 5 ) 2 La(NCMe) 2 (THF)][BPh 4 ], 5 - La , was also crystallographically characterized. A similar result was observed with the yttrium metallocene of the trimethylsilyl-containing ligand (C 5 H 4 SiMe 3 ) 1− : coordination of only three nitriles is found in [(C 5 H 4 SiMe 3 ) 2 Y(NCMe) 3 ][BPh 4 ], 6 - Y , which has a 136.8° (C 5 Me 5 ring centroid)–Y–(C 5 Me 5 ring centroid) angle. [ABSTRACT FROM AUTHOR]

A comprehensive review on the synthesis, reactions and applications centered on the highly stable and sterically hindered cobalt sandwich compound (η 5 -Cp)Co(η 4 -C 4 Ph 4 ) is presented. The derivatization of the cyclopentadienyl and cyclobutadiene rings, reactions, structural properties and applications, particularly in the field of asymmetric catalysis of (η 5 -Cp)Co(η 4 -C 4 Ph 4 ) and its derivatives and analogues are discussed. The chemistry of this cobalt sandwich compound is also compared with analogous derivatives of ferrocene. [ABSTRACT FROM AUTHOR]

The reaction of Ir(CO) 2 ( η 5 -C 5 HMe 4 ) with Mo 2 Ir 2 (μ-CO) 3 (CO) 7 ( η 5 -C 5 H 5 ) 2 affords a complex mixture from which three structurally-characterized products were obtained following thin-layer chromatography. Mo 3 Ir 3 (μ 3 -O)(μ-CO) 3 (CO) 8 (η 5 -C 5 H 5 ) 3 ( 1 ) is Effective Atomic Number (EAN) Rule EAN-precise and possesses an edge-bridged trigonal bipyramidal core with the face-capping oxo ligand located in a Mo 2 Ir 2 butterfly cleft in the structure. Mo 4 Ir 4 (μ-CO) 4 (CO) 9 (η 5 -C 5 H 5 ) 4 ( 2 ) possesses four electrons less than the Polyhedral Skeletal Electron Pair Theory (PSEPT)-expected count for a capped pentagonal bipyramidal cluster with the apical atoms within bonding distance. Mo 3 Ir 5 (μ-CO) 3 (Cl)(CO) 6 (η 5 -C 5 H 5 ) 3 (η 5 -C 5 HMe 4 ) ( 3 ) possesses a tetracapped tetrahedral core and has six electrons less than the PSEPT-predicted electron count. The core geometries exhibited by clusters 2 and 3 have previously only been observed for clusters including significant group 10 and group 11 metal content. [ABSTRACT FROM AUTHOR]

A new family of eight ruthenium(II)-cyclopentadienyl bipyridine derivatives, bearing nitrogen, sulfur, phosphorous and carbonyl sigma bonded coligands, has been synthesized. Compounds bearing nitrogen bonded coligands were found to be unstable in aqueous solution, while the others presented appropriate stabilities for the biologic assays and pursued for determination of IC 50 values in ovarian (A2780) and breast (MCF7 and MDAMB231) human cancer cell lines. These studies were also carried out for the [ 5 : HSA] and [ 6 : HSA] adducts (HSA = human serum albumin) and a better performance was found for the first case. Spectroscopic, electrochemical studies by cyclic voltammetry and density functional theory calculations allowed us to get some understanding on the electronic flow directions within the molecules and to find a possible clue concerning the structural features of coligands that can activate bipyridyl ligands toward an increased cytotoxic effect. X-ray structure analysis of compound [Ru(η 5 -C 5 H 5 )(bipy)(PPh 3 )][PF 6 ] ( 7 ; bipy = bipyridine) showed crystallization on C2/c space group with two enantiomers of the [Ru(η 5 -C 5 H 5 )(bipy)(PPh 3 )] + cation complex in the racemic crystal packing. [ABSTRACT FROM AUTHOR]

The cyclopentadienyliridium hydrides Cp 2 Ir 2 H n (Cp = η 5 -C 5 H 5 ; n = 6, 4, 2, 0), and CpIrH n ( n = 4, 2) related to the experimentally known pentamethyl cyclopentadienyliridium hydrides Cp ∗ 2 Ir 2 H n (Cp ∗ = η 5 -Me 5 C 5 ; n = 6, 2) and Cp ∗ IrH 4 have been investigated by density functional theory. The lowest energy Cp 2 Ir 2 H n ( n = 6, 4, 2) structures are predicted to have terminal Cp rings with the central Ir 2 unit bridged by two hydrogen atoms. For the hexahydride Cp 2 Ir 2 H 6 , such doubly bridged Cp 2 Ir 2 (μ-H) 2 H 4 structures are bent, leading to trans and cis structures of similar energies with an unbridged Cp 2 Ir 2 H 6 isomer lying only ∼4 kcal/mol above the bridged structures. This suggests fluxional behavior consistent with experimental data on the temperature dependence of the proton NMR spectrum of the closely related Cp ∗ 2 Ir 2 H 6 . The tetrahydride Cp 2 Ir 2 H 4 is predicted to undergo slightly exothermic disproportionation into Cp 2 Ir 2 H 6 + Cp 2 Ir 2 H 2 and thus not be a viable species. This is consistent with the failure to find any Cp ∗ 2 Ir 2 H 4 in the Cp ∗ 2 Ir 2 H n systems. The doubly bridged dihydride Cp 2 Ir 2 (μ-H) 2 is a particularly favorable species since it lies more than 18 kcal/mol in energy below any other isomer. Higher energy Cp 2 Ir 2 H n ( n = 4, 2) structures have one or two bridging Cp rings and exclusively terminal hydrogen atoms. Related structures are the lowest energy structures for the hydride-free Cp 2 Ir 2 . A higher energy Cp 2 Ir 2 structure consists of two CpIr units linked solely by an Ir–Ir bond. Analysis of the frontier molecular orbitals indicates this Ir–Ir bond to be the quadruple bond required to give each iridium atom the favored 18-electron configuration. However, this quadruple bond is a 2 σ + 2π bond with no δ components and thus differs from the σ + 2π + δ quadruple bond found in the long-known Re 2 Cl 8 2− . [ABSTRACT FROM AUTHOR]

The chemistry of arene complexes of uranium has for over half a century been an important facet of organoactinide chemistry. Within this extensive and burgeoning field, in the past two decades inverted sandwich complexes have emerged incorporating cyclobutadienyl, arene, cycloheptatrienyl, and cyclooctatetraenyl ligands. Herein, the field is reviewed with an emphasis on well-defined molecular species that have been unambiguously characterised by X-ray crystallography. [ABSTRACT FROM AUTHOR]

A series of tetramethyl-(Cp′) and pentamethylcyclopentadienyl (Cp*) metal complexes (η 5 -C 5 Me 4 R)ZrCl 2 L CO (R = H( 1 ), Me( 2 )) and (η 5 -C 5 Me 4 R)HfCl 2 L CO (R = H( 3 ), Me( 4 )) where L CO is a bifunctional β -diketiminate ligand [2-(MeO)–C 6 H 4 )]NC(Me)CHC(Me)N[2-(MeO)–C 6 H 4 )] (L CO ) were prepared from corresponding tetramethyl- and (pentamethylcyclopentadienyl)metal trichlorides and the lithium precursor LiL CO . All complexes were characterized by their melting point, elemental analysis, 1 H and 13 C NMR spectroscopy, IR spectroscopy. In addition their solid-state structures were determined by X-ray diffraction techniques. In all cases, a pseudo-tetragonal pyramidal coordination environment of the metal centre with cyclopentadienyl ligand on the top and nearly isobidentately bonded nitrogen atoms of the chelating L CO ligand in an open η 5 -fashion was observed. The oxygen atoms positioned at the diketiminate periphery remained uncoordinated to transition metal in the solid phase as well as in solution. Besides the desired compounds, two hafnium complexes bearing either 2-methoxyaniline or 2-methoxyanilide ligands were isolated and structurally characterized as minor decomposition and dismutation products of 3 and 4 , respectively. Complexes containing the β -diketiminate ligand as well as its precursors were tested for catalytic activity in the polymerization of ethylene using different activators (MAO, MMAO and Al i Bu 3 /(Ph 3 C) + [B(C 6 F 5 ) 4 ] − ). Among the new complexes, the best activity as high as 340 kg PE (mol M hbar) −1 was achieved with 1 /Al i Bu 3 /(Ph 3 C) + [B(C 6 F 5 ) 4 ] − system. In attempts to clarify the activation process of group 4 metal-based precatalysts, the synthesis and NMR studies of the aluminium β -diketiminate complex Al( i Bu) 2 L CO were also carried out. [ABSTRACT FROM AUTHOR]

[Display omitted] The kinetics of halide exchange in cyclopentadienylruthenium bis(triarylphosphine) halide complexes CpRu(PAr 3) 2 X (1a X = Cl, 1b X = Br, 1c X = I; X′= Cl, Br, Ar = C 6 H 5 , 2 Ar = p- CH 3 OC 6 H 4 , X = Cl, X′= Br and 3 Ar = p- FC 6 H 4 , X = Cl, X′ = Br) have been measured and the results interpreted with respect to two possible mechanisms: halide dissociation vs phosphine dissociation. Halide exchange between n Bu 4 NX′ and 1 – 3 in fluorobenzene under pseudo-first order conditions is found to be first order in 1 – 3. Relative rates of halide exchange follow the order: 1a > 1b > 1c > 2 ≈ 3 with activation parameters ΔH† = 117 ± 6 kJ/mol and ΔS† = 44 ± 18 J/mol-K (1a , X′ = Br) and ΔH† = 120 ± 14 kJ/mol ΔS† = 50 ± 45 J/mol-K (1b , X′ = Cl). Plots of k obs vs [X′–] for 1 and 2 are consistent with a two-term rate law where k obs = (k 1 + k 2 [X′–]) while reactions of 3 are independent of the halide concentration. The rate data are consistent with phosphine dissociation as the rate determining step followed by a slightly faster reaction with halide ions where the dissociated phosphine competes effectively with halide for the open coordination site in a CpRu(PAr 3)X intermediate. [ABSTRACT FROM AUTHOR]

The coordination chemistry of the previously neglected 2,4-di( tert -butyl)pentadienyl (Pdl′) ligand with transition metals is explored. Several open metallocenes [(η 5 -Pdl′) 2 M] (M = Ti ( 3 ), V ( 4 ) and Cr ( 5 )) were prepared and characterized by various spectroscopic techniques and X-ray diffraction. Attempts to prepare the open ferrocene [(η 5 -Pdl′) 2 Fe] were hampered by its high thermal instability, which leads to the formation of iron metal and 2,4,7,9-tetra- tert -butyl-1,3,7,9-decatetraene ( 2 ). Nevertheless, the half-open ferrocene [(η 5 -Pdl′)Fe(η 5 -Cp″)] (Cp″ = 1,2,4-(Me 3 C) 3 C 5 H 2 , 6 ) and mono(pentadienyl) iridium complex [(η 5 -Pdl′)Ir(η 4 -cod)] ( 9 ) were successfully synthesized. The electronic and molecular structures of the half-open ferrocene [(η 5 -Pdl′)Fe(η 5 -Cp″)] ( 6 ) and its closed analogue [(η 5 -Cp′)Fe(η 5 -Cp″)] ( 7 , Cp′ = 1,3-(Me 3 C) 2 C 5 H 3 ) were compared. Complex 6 is significantly more encumbered than 7 , as shown by the short Pdl′ cent –Fe distance. Clean oxidation of 6 and 7 can be accomplished electrochemically and chemically to give the half-open ferrocenium 6 + and closed ferrocenium 7 + , respectively, and in both cases steric strain is released upon oxidation. On heating of 6 + to 152 °C in the solid state H 2 and isobutene is eliminated to give [(η 5 -Cp′) 2 Fe] + ( 8 ). [ABSTRACT FROM AUTHOR]

Synthesis, reactivity and application of cyclopentadienyl ruthenium complexes with naphthalene and other polycyclic aromatic ligands (polyarenes) are reviewed. The parent naphthalene complex [CpRu(C10H8)]+ is readily obtained from ruthenocene while its substituted analog [Cp*Ru(C10H8)]+ is prepared by direct reaction of RuCl3•xH2O with Cp*H and C10H8. More sophisticated polyarene complexes including binuclear species are synthesized from the half-sandwich precursors [Cp*RuCl2]2, [Cp*RuCl]4, and [(C5R5)Ru(MeCN)3]+. Coordinated naphthalene in [CpRu(C10H8)]+ can be exchanged for various 2-electron ligands under thermal or photochemical conditions giving half-sandwich complexes CpRuL2X and [CpRuL3]+ (L = phosphines, N-heterocycles, dienes; X = Cl, Br, I, N3). Similar reactions of [CpRu(C10H8)]+ with cyclopentadienes or arenes produce sandwich compounds CpRu(C5R5) or [CpRu(arene)]+, respectively. The ability of [CpRu(C10H8)]+ to generate the catalytically active species [CpRuLx]+ can be used to promote anti-Markovnikov hydration and cyclotrimerization of alkynes, as well as for enantioselective Carroll rearrangement. In overall it can be concluded that stable and easily accessible [(C5R5)Ru(polyarene)]+ complexes represent convenient precursors for organometallic synthesis and catalysis. [ABSTRACT FROM AUTHOR]

Atomic layer deposition of ZrO2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe2)3 and H2O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350 °C. In this temperature range growth rate of 0.08-0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200 °C and higher temperatures contained tetragonal and monoclinic phases of ZrO2. The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250 °C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe2)3 and H2O at 250-350 °C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm³, respectively, being close to the highest values obtained for films deposited from ZrCl4 and H2O. The former process ensured, however, more uniform nucleation of ZrO2 on graphene than the latter process did. [ABSTRACT FROM AUTHOR]

Abstract: The series of cobaltathiaboranes CpCoSB n H n (n =6, 7, 8, 9, 10) related to the experimentally known CpCoSB8H8 and CpCoSB10H10 have been investigated by density functional theory. The lowest energy CpCoSB n H n (n =6–10) structures are the closo deltahedra in accord with expectations for these 2n +2 Wadean skeletal electron systems. In the lowest energy such structures the sulfur atom is located at a lowest degree vertex and the cobalt atom at a highest degree vertex. An alternative bicapped octahedral CpCoSB6H6 structure having the sulfur atom at a degree 3 capping vertex lies only ∼7kcal/mol above the bisdisphenoid global minimum. For the 12-vertex CpCoSB10H10 system the three possible structures based on a B10CoS regular icosahedron lie more than 50kcal/mol in energy below any non-icosahedral structures. The relative energy ordering of ortho

Abstract: We here report the synthesis of new cyclopentadienyl ruthenium(II) complexes of general formula [(η 5-C5H5)Ru(PP)(L)]+ (PP = two triphenylphosphine, 1,2-diphenylphosphinoethane), isolated as salts, with L being galactose and fructose carbohydrate derivative ligands, N-coordinated to the metal centre by nitrile, tetrazole and 1,3,4-oxadiazole moieties. The ten new organometallic compounds were fully characterized by FT-IR, 1H, 13C, and 31P NMR spectroscopies, and by elemental analysis. The cytotoxicity of the ruthenium(II) compounds was tested on HeLa cancer cells (cervical carcinoma), unveiling IC50 values in the low micromolar range. [Copyright &y& Elsevier]

Highlights: [•] A series of titanium complexes [Cp(Ind)-(bridge)-thienyl]TiCl3 have been synthesized. [•] No intramolecular coordination could be observed by X-ray study. [•] The substitutents at the 5-position of the thienyl group can increase the trimerization activity. [•] Indenyl complexes are more active and more tolerant of temperature than Cp complexes. [Copyright &y& Elsevier]

Abstract: A new family of “FeII(η5-C5H5)” half sandwich compounds bearing a N-heteroaromatic ligand coordinated to the iron center by a nitrile functional group has been synthesized and fully characterized by NMR and UV–Vis spectroscopy. X-ray analysis of single crystal was achieved for complexes 1 and 3, which crystallized in the monoclinic P21/c and monoclinic P21/n space groups, respectively. Studies of interaction of these five new complexes with plasmid pBR322 DNA by atomic force microscopy showed very strong and different types of interaction. Antiproliferative tests were examined on human leukemia cancer cells (HL-60) using the MTT assay, and the IC50 values revealed excellent antiproliferative activity compared to cisplatin. [Copyright &y& Elsevier]

Abstract: The structures and thermochemistry of the binuclear cyclopentadienylcobalt carbonyl boronyls Cp2Co2(BO)2(CO) n (Cp = η5-C5H5; n = 2, 1, 0) were investigated by density functional theory. Low energy structures were found of the following types: (1) Structures in which the BO groups are all one-electron donors analogous to the isoelectronic Cp2Fe2(CO) n+2 structures; (2) Structures in which the two BO groups have coupled to form bridging B2O2 ligands, which may be either four- or six-electron donors; (3) Structures with three-electron donor bridging BO groups, bonded to one metal through the boron atom and to the other metal through the oxygen atom. The lowest energy Cp2Co2(BO)2(CO)2 structures are singlet trans and cis isomers of doubly bridged structures analogous to the well-known isoelectronic Cp2Fe2(CO)2(μ-CO)2. The lowest energy Cp2Co2(BO)2(CO) structure is a triplet triply bridged structure analogous to the isoelectronic stable triplet state molecule Cp2Fe2(μ-CO)3. Higher energy Cp2Co2(BO)2(CO) structures have trans or cis bridging B2O2 ligands. The lowest energy Cp2Co2(BO)2 structure is a triplet state structure with a six-electron donor bridging trans-η4-μ-B2O2 ligand. The lowest energy singlet Cp2Co2(BO)2 structure has two one-electron donor bridging μ-BO groups and a formal Co Co triple bond similar to the predicted lowest energy Cp2Fe2(CO)2 structure. [Copyright &y& Elsevier]

Abstract: The allyl molybdenum(II) complex bearing tetrafluoro-4-pyridyl substituted cyclopentadienyl ligand, [(η 3-C3H5){η 5-C5H3(C5F4N)}Mo(CO)2], was synthesized and characterized by analytical and spectroscopic methods. This compound was found to be suitable precursor for complexes of the type [{η 5-C5H4(C5F4N)}Mo(CO)2(NNL)][BF4] where NNL is N,N-chelating ligand. The biological study has shown that these complexes are cytotoxic active toward human leukemia cells MOLT-4. The cytotoxicity strongly depends on nature of the coordinated N,N-chelating ligand. The compounds bearing 1,10-phenanthroline (phen) and 2,2′-biquinoline (bq) are only medium active while the complexes with 4,7-diphenyl-1,10-phenanthroline (4,7-Ph2-phen) and 5-amino-1,10-phenanthroline (5-NH2-phen) show considerably higher activity than cisplatin. This study further describe the X-ray structures of [(η 3-C3H5){η 5-C5H4(C5F4N)}Mo(CO)2], [(η 3-C3H5){η 5-C5H3(1,3-C5F4N)2}Mo(CO)2], [{η 5-C5H4(C5F4N)}Mo(CO)2(phen)][BF4] and [{η 5-C5H4(C5F4N)}Mo(CO)2(5-NH2-phen)][BF4]. [Copyright &y& Elsevier]

Abstract: A novel water soluble organometallic compound, [RuCp(mTPPMSNa)(2,2′-bipy)][CF3SO3] (TM85, where Cp=η5-cyclopentadienyl, mTPPMS=diphenylphosphane-benzene-3-sulfonate and 2,2′-bipy=2,2′-bipyridine) is presented herein. Studies of interactions with relevant proteins were performed to understand the behavior and mode of action of this complex in the biological environment. Electrochemical and fluorescence studies showed that TM85 strongly binds to albumin. Studies carried out to study the formation of TM85 which adducts with ubiquitin and cytochrome c were performed by electrospray ionization mass spectrometry (ESI-MS). Antitumor activity was evaluated against a variety of human cancer cell lines, namely A2780, A2780cisR, MCF7, MDAMB231, HT29, PC3 and V79 non-tumorigenic cells and compared with the reference drug cisplatin. TM85 cytotoxic effect was reduced in the presence of endocytosis modulators at low temperatures, suggesting an energy-dependent mechanism consistent with endocytosis. Ultrastructural analysis by transmission electron microscopy (TEM) revealed that TM85 targets the endomembranar system disrupting the Golgi and also affects the mitochondria. Disruption of plasma membrane observed by flow cytometry could lead to cellular damage and cell death. On the whole, the biological activity evaluated herein combined with the water solubility property suggests that complex TM85 could be a promising anticancer agent. [Copyright &y& Elsevier]