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• New CO delivery systems based on the inclusion of metal carbonyls in cucurbit[8]uril. • Myoglobin CO-release assays performed for free/encapsulated [(η5-C5H4R)Mo(CO)3CH3]. • A wide range of rates for spontaneous CO-release was observed in aqueous systems. • CO release is attenuated by both introduction of r = CO2Me and by CB8 encapsulation. • UV irradiation promotes CO release from free/encapsulated [(η5-C5H4CO2Me)Mo(CO)3CH3]. The monosubstituted cyclopentadienyl half-sandwich molybdenum(II) tricarbonyl complex [(η 5-C 5 H 4 CO 2 CH 3)Mo(CO) 3 CH 3 ] (1) and its 1:1 inclusion compound with cucurbit[8]uril (1 @CB8) have been prepared and characterised by elemental and thermogravimetric analyses, powder X-ray diffraction, diffuse reflectance UV–vis, solid-state 13C{1H} MAS NMR, FT-IR, and Raman spectroscopies. The CO-releasing behaviours of 1, 1 @CB8 and, for comparison, [(η 5-C 5 H 5)Mo(CO) 3 CH 3 ] (2) and its 1:1 inclusion complex with CB8, were assessed using a deoxymyoglobin-carbonmonoxymyglobin assay. For assays performed in the dark at 37 °C, complex 1 undergoes thermally assisted spontaneous CO release, with ca. 0.5 equivalents of CO being released after 6 h. The half-life (t 1/2) of 325 min identifies 1 as a slow releaser when compared to complex 2 bearing the unsubstituted cyclopentadienyl ligand (t 1/2 = 25 min). CO release from 1 was promoted by exposure to UV light (t 1/2 = 85 min), establishing the complex as a photochemically activated CO-releasing molecule (photoCORM). For 1 @CB8, t 1/2 for photo-assisted CO release increased to ca. 7 h, and for 2 @CB8 the dark-release t 1/2 increased to 165 min, showing that molecular acceptors like cucurbiturils can be used effectively as second-sphere ligands to modulate the CO release profile of CORMs. [Display omitted] [ABSTRACT FROM AUTHOR]

• A new glycine-bisphenol molybdenum(VI) complex, SBA@AP-GDC-Mo, immobilized on ordered mesoporous silica was synthesized and fully characterized. • SBA@AP-GDC-Mo is an efficient and selective heterogenous catalyst for chemoselective oxidation of thioethers to sulfoxides and sulfones. • The advantages of SBA@AP-GDC-Mo include high activity under eco-friendly, mild conditions (e.g., room temperature, organic solvent-free or in ethanol) and reusability for at least four cycles. Herein we introduce a new glycine-bisphenol molybdenum(VI) complex, SBA@AP-GDC-Mo, immobilized on ordered mesoporous silica SBA-15 (Santa Barbara Amorphous) as an efficient and selective heterogenous catalyst. SBA@AP-GDC-Mo was fully characterized by Fourier transform-infra red (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), field emission-transmission electron microscopy (FE-TEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and Barrett–Joyner–Halenda (BJH) and Brunauer–Emmett–Teller (BET) adsorption isotherms. The catalytic performance of SBA@AP-GDC-Mo was evaluated in the chemoselective oxidation of sulfides to sulfoxides and sulfones and found to be superior to our previously reported diamine–bisphenol molybdenum(VI) catalyst. The advantages of SBA@AP-GDC-Mo include high activity and better chemoselectivity under mild and eco-friendly conditions (e.g., ambient temperature using aqueous or aqueous–ethanolic solutions), recyclable for at least four cycles and easier overall synthesis in good yields including tethering of the ligand to the support. [Display omitted] [ABSTRACT FROM AUTHOR]

• First report on aluminum reductant for the deoxydehydration (DODH) of glycols in the presence of pincer type Mo-catalyst. • Among the metal reductants examined, Al was found the best. • Easy separation from reductant from heterogeneous mixture. • Reaction is very easy to operate and carried out at 165–170 °C. • Moderate to high yield of DODH product formation. This study demonstrates that the zero-valent elements aluminum, zinc, iron, manganese, copper, and carbon are effective reductants for the ONO-pincer ligated molybdenum dioxo catalyzed deoxydehydration (DODH) of polyols. The reductants (elements) and their oxidized products remain insoluble during the reaction and can be easily separated. The cis -MoO 2 (dipic)L (dipic = pyridine-2,6-dicarboxylate); L=HMPA (Hexamethylphosphoramide), THF), and cis -MoO 2 (4-Chloro-dipic) HMPA catalysts (1) were found to be effective for the DODH of polyols. The stoichiometric experiments indicate a probable transition from Mo (VI) to Mo (IV) in the redox cycle for the DODH of polyols. [Display omitted] [ABSTRACT FROM AUTHOR]

The reaction of fac -[M(OTf)(CO) 3 (N–N)](M = Mn, Re; N–N = 2,2′-bipyridine, 1,10-phenanthroline) complexes with in situ generated LiSEt afforded immediately, in THF at low temperature, the corresponding mononuclear terminal thiolato complexes fac -[M(SEt)(CO) 3 (N–N)](1-2a,b). Using an analogous synthetic strategy, tungsten and molybdenum (II) alkyl- and arylthiolatos of formula cis -[M(SR)(η3-allyl)(CO) 2 (N–N)] (3-6a,b) have been obtained. Preliminary reactions of the more reactive molybdenum thiolato complexes towards dimethylacetylenedicarboxylate led to Z -alkenyl products (7a,b), resulting from the insertion of the organic unsaturated electrophile into the Mo–S bond. For each new type of compound, one representative has been characterized in the solid state by X-ray diffraction. Image 1 • New terminal Re(I) and Mo(II) mononuclear thiolato complexes have been obtained. • The new complexes have been fully characterized in solution (IR, NMR spectroscopies). • The structure of [Re(SEt)(CO) 3 (bipy)] has been determined by X-ray diffraction. • The structure of [Mo(allyl)(SEt)(CO) 2 (phen)] has been determined by X-ray diffraction. • The Mo ethylthiolato complexes insert DMAD into the Mo–S bond affording Z -alkenyls [ABSTRACT FROM AUTHOR]

Abstract TADDOL-derived P-donor ligands are of interest as ligands in transition metal catalyzed transformations; however, few studies have been conducted on the steric and electronic properties of P-donor ligands derived from TADDOL. To gain more insight into these properties four tetracarbonylmolybdenum(0) and two pentacarbonyltungsten(0) complexes of monodentate P-donor ligands derived from TADDOL have been studied. These studies show that exchanging the chloro substituent on the phosphorus for OMe increases the donor ability of the ligand and that the cis -tetracarbonylmolybdenum(0) complex of the ligand having the OMe substituent spontaneously isomerizes in solution. X-ray crystallographic analyses indicate that the orientations of the 1,3,2-dioxaphosphepane ring and the aryl substituents are not always conserved, even within the same complex. Graphical abstract Image 1 Highlights • Synthesis of molybdenum and tungsten complexes with monodentate TADDOL-derived P-donor ligands. • Cis-trans equilibria in Mo(CO) 4 (TADDOL-derived P-donor ligand) 2 complexes catalyzed by HgCl 2. • Hydroformylation data suggests chirality transfer is poor with monodentate ligands. [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]

The xanthine oxidase (XO) family is a group of molybdenum-containing enzymes that catalyze the transfer of an oxygen atom from water to a substrate, such as xanthine or aldehyde. The proposed mechanism for the reductive half-reaction of xanthine oxidase involves nucleophilic addition of Mo-bound hydroxide to the substrate and hydride transfer from the substrate to sulfido group (Mo=S) at the molybdenum cofactor (Moco) reaction center. A DFT study of a mechanism involving the near-by glutamic acid (Glu) residue for the oxidation of several model substrates found that the direct involvement of the Glu residue side chain significantly increases the reactivity of the cofactor. The reaction is stepwise with a hydride transfer as the rate determining step. On the basis of mechanistic studies, a QM model was established to search the potential reactive fragments for mechanism-based inhibitors. Two important parameters were designed to evaluate each fragment: the activation enthalpy (ΔH ≠ ) which estimates how effectively an inhibitor competes with xanthine to react with the Moco site, and the enthalpy associated with release of the product ( ΔH ) which estimates how easily the product in product complex ( PRO ) could be replaced by a water molecule. The computational findings add to our understanding of the catalytic mechanism of xanthine oxidase, and also assist the screening of mechanism-based inhibitors for this important drug target. [ABSTRACT FROM AUTHOR]

Tetracarbonylmolybdenum(0) complexes of the type cis -[Mo(CO) 4 (L)] containing chiral 7-(1-pyrindanyl) amine ligands were prepared and found to be effective precatalysts for the epoxidation of achiral ( cis -cyclooctene) and prochiral (DL-limonene and trans -β-methylstyrene) olefins at 55 °C. Epoxides were the only products formed from cis -cyclooctene (100% yield) and trans -β-methylstyrene (100% selectivity at 82–85% conversion), and the main products formed from DL-limonene (80–82% 1,2-epoxide selectivity at 85% conversion). Characterization of recovered catalysts revealed that the precatalysts were transformed in situ to stable polyoxomolybdate salts containing the β -octamolybdate anion [ β -Mo 8 O 26 ] 4− , which was responsible for the catalytic reaction. [ABSTRACT FROM AUTHOR]

The indenyl molybdenum carbonyl complexes [IndMo(CO) 2 (L) n ]BF 4 (L = NCMe with n = 3 ( 1 ), 2,2′-bipyridine ( 2 ) or 1,4,7-trimethyltriazacyclononane ( 3 ) with n = 1) promote epoxide alcoholysis under moderate reaction conditions. Complexes 1 and 2 showed the best performance for the alcoholysis of styrene oxide with different alcohol nucleophiles (acting as both reactant and solvent), leading to the corresponding 2-alkoxy-2-phenylethanol with 100% yield at 10 min and 35 °C. These catalytic results are far superior to those found for previously studied molybdenum carbonyl complexes. An efficient procedure for catalyst recovery and reuse without decrease in reaction rate is described. [ABSTRACT FROM AUTHOR]

In an effort to synthesize trithiocarbonate complexes of molybdenum and ruthenium, we carried out the reaction of CS 2 with the intermediates, obtained from the reaction of [Cp # ML 3 X], ( 1 : Cp # = C 5 Me 5, M = Mo, L 1 = L 2 = L 3 = CO, X = Me; 2 : Cp # = C 5 H 5, M = Ru, L 1 = L 2 = PPh 3 , X = Cl and 3 : Cp # = C 5 H 5, M = Fe, L 1 = L 2 = CO, X = I) and [LiBH 4 ⋅thf]. The reactions led to formation of the trithiocarbonate complexes [Cp*Mo(CO) 2 (μ-ɳ 2 :ɳ 1 -CS 3 )(CO) 3 MoCp*] ( 4 ) [Cp*Mo(CO) 2 (ɳ 2 -S 2 CSMe)] ( 5 ) and [Cp*Mo(CO) 2 (ɳ 2 -S 2 CMe)] ( 6 ) in moderate yields. Treatment of [CpRu(PPh 3 ) 2 Cl] ( 2 ) with [LiBH 4 ⋅thf] followed by mild pyrolysis of CS 2 yielded the trithiocarbonate ruthenium complex [CpRuPPh 3 (ɳ 2 -S 2 CSMe)] ( 7 ). All the new compounds have been characterized by various spectroscopic techniques and the structures of compounds 4 , 5 and 7 were unequivocally established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

Tetracarbonylmolybdenum(0) complexes of the type cis -[Mo(CO) 4 (L)] are attractive synthetic precursors of high oxidation state oxomolybdenum catalysts since the byproducts (CO/CO 2 ) readily separate from the reaction mixture, facilitating separation/purification procedures (e.g. avoiding contamination/acidification of the medium for halide (X)-containing precursors such as [Mo( η 3 -C 3 H 5 )Cl(CO) 2 (L)]). In this work, the conversion of the tetracarbonyl complex cis -[Mo(CO) 4 (ppp)] (ppp = 2-(1-pentyl-3-pyrazolyl)pyridine) to oxomolybdenum compounds has been studied. The molybdenum compounds prepared were explored for liquid phase oxidation and acid catalysis, specifically the epoxidation of cis -cyclooctene with hydroperoxide oxidants, and the alcoholysis of styrene oxide. The routes for the conversion of the cis -[Mo(CO) 4 (ppp)] precursor to oxomolybdenum compounds, during either the synthesis ( ex situ ) or catalytic ( in situ ) processes (involving isolation/characterisation of metal species after the catalytic runs), were studied for the different catalytic systems, which helped establish relationships between the type of metal species formed and the catalytic performance. Catalyst recyclability was investigated using a homogeneous catalytic ionic liquid-standing approach. [ABSTRACT FROM AUTHOR]

• Commercially available catalyst. • Sustainable Microwave Assisted Catalysis. • Enhanced reaction rate. The effectiveness of microwave irradiation in promoting the deoxydehydration of aliphatic diols using dioxomolybdenum catalysts has been evaluated. The commercially available molybdenum precursor MoO 2 (acac) 2 was found to be a superior catalyst as compared to dioxomolybdenum complexes stabilized by aminebisphenol ligands under these conditions. Octane-1,2-diol and decane-1,2-diol were converted to the corresponding olefins in 40−53% yields in 40 mins at 220−230 οC; this is a significant reduction in reaction time and higher activity when compared to reactions performed using conventional heating. More importantly, a similar yield (48%) of 1-decene could be achieved within 10 mins from a reaction carried out at 250 οC. [Display omitted] [ABSTRACT FROM AUTHOR]

• A facile method was put forward to prepare the catalyst Mo(TC)/GO. • The catalyst showed high activity in the synthesis of benzothiazole derivatives. • Short reaction time and excellent yields of products. • The catalytic could be reused seven times without any noticeable loss of activity This paper presented a novel amino-modified nano-graphene oxide supported thiophene-2-carbaldehyde Mo-complex (Mo(TC)/GO) catalyst prepared and characterized by FT-IR, SEM, TEM, TGA, EDX, BET, XRD, and N 2 adsorption–desorption techniques. The catalyst presented an outstanding performance for synthesizing benzothiazole derivatives through a reaction between benzyl alcohol derivatives and 2-aminothiophenol. The heterogeneous catalyst could be facial separated and reused by filtration without any substantial decline in its catalytic activity even after five runs. [Display omitted] [ABSTRACT FROM AUTHOR]

Inter-ring haptotropic rearrangements (IRHRs) are well-known phenomena in fluxional ogranometallic chemistry. They are mainly observed for transition metal complexes with polyaromatic ligands (PALs), but are usually limited to PALs without heteroatoms. Here, we report DFT studies of recent experimentally observed IRHRs in heterocyclic complexes of Mo. Four different ligands (quinoline, isoquinoline, quinoxaline, and indolyl) have been investigated. Overall, structural and energetic trends agree well with available experimental data. In addition, mechanistic trends and heteroatom participation are discussed and elucidated to further understanding of IRHRs in heterocyclic polyaromatic complexes in particular, and haptotropic processes in general. [ABSTRACT FROM AUTHOR]

Thermolysis of tetrahedral Mo 2 Ir 2 (μ-CO) 3 (CO) 7 (η 5 -C 5 H 5 ) 2 in refluxing toluene affords small amounts of Mo 3 Ir 3 (μ 4 -η 2 -CO)(μ 3 -CO)(CO) 10 (η 5 -C 5 H 5 ) 3 ( 1) . Reaction of 1 with Rh(CO) 2 (η 5 -C 5 Me 5 ) in refluxing dichloromethane gives Mo 3 RhIr 3 (μ-CO) 4 (CO) 7 (η 5 -C 5 H 5 ) 3 (η 5 -C 5 Me 5 ) ( 2 ) in moderate yield. X-ray diffraction studies show the metal cores adopt edge-bridged trigonal bipyramidal and bicapped trigonal bipyramidal structures, respectively. Cluster 2 is electron precise with 96 CVE, in contrast to the only precedent group 6-group 9 mixed-metal cluster with an identical core geometry, the 94 CVE W 3 Ir 4 (μ-H)(CO) 12 (η 5 -C 5 H 5 ) 3 ( 3 ). DFT studies have been employed to rationalize the contrasting behavior of 2 and 3 . Time-dependent DFT has been employed to assign the key transitions in the linear optical absorption spectrum of 2 . [ABSTRACT FROM AUTHOR]

The 32-electron benzylidyne-bridged complex [Mo 2 Cp 2 ( μ -CPh)( μ -PCy 2 )(CO) 2 ] reacted with elemental chalcogens E n (E = S, Se) at 333 K to give the corresponding derivatives trans -[Mo 2 Cp 2 { μ - η 2 : η 2 -C(Ph)E}( μ -PCy 2 )(CO) 2 ], following from addition of a chalcogen atom to the Mo 2 C face of the central Mo 2 PC core in the parent compound, whereby a 5-electron donor, bridging chalcogenoacyl ligand was formed (Mo−Mo = 2.8662(5) Å, C−S = 1.757(5) Å in the thioacyl complex). These thermally stable products did not undergo decarbonylation under irradiation with visible-UV light, but instead rearranged into the corresponding cis -dicarbonyl isomers cis -[Mo 2 Cp 2 { μ - η 2 : η 2 -C(Ph)E}( μ -PCy 2 )(CO) 2 ] (Mo−Mo = 2.9208(5) Å, C−S = 1.745(5) Å in the thioacyl complex), in a process where no reaction intermediates were detected. The coordination of the chalcogenoacyl ligand in the cis -dicarbonyl isomers is analogous to that observed in the corresponding trans isomers, and involves the selective positioning of the 3-electron donor chalcogen atom trans to the bridging phosphanyl ligand, a structural trend common to related complexes with isoelectronic η 2 : η 2 bridging groups such as iminoacyl, formimidoyl and diphosphenyl ligands. [ABSTRACT FROM AUTHOR]

The reaction of [MoBr(dppe)(η-C 7 H 7 )] (dppe = Ph 2 PCH 2 CH 2 PPh 2 ) with HC CC CSiMe 3 and Na[BPh 4 ] in 1:1 NHEt 2 /THF as solvent yields the aminoallenylidene complex [Mo{C C C(Me)NEt 2 }(dppe)(η-C 7 H 7 )][BPh 4 ], [ 1 ][BPh 4 ]. The reaction likely proceeds via nucleophilic addition of NHEt 2 at C γ of a butatrienylidene intermediate. Structural and spectroscopic characterisation of [ 1 ][BPh 4 ] indicate a significant contribution of an iminium alkynyl resonance form to the overall structure of the heteroatom stabilised allenylidene ligand. The X-ray structural study of [ 1 ][BPh 4 ] determines a Mo C α bond length of 2.077(3) Å, intermediate between that of the cumulenic diphenylallenylidene analogue [Mo(C C CPh 2 )(dppe)(η-C 7 H 7 )][PF 6 ] (1.994(3) Å) and the alkynyl compound [Mo(C CPh)(dppe)(η-C 7 H 7 )] (2.138(5) Å). Complex [ 1 ][BPh 4 ] undergoes a reversible one-electron oxidation with E ½ = −0.19 V with respect to the FeCp 2 /FeCp 2 + couple and the stable 17-electron radical dication [ 1 ] 2+ is readily observed by spectroelectrochemical methods. IR spectroelectrochemistry in CH 2 Cl 2 demonstrates that the ν (CCC) stretch, characteristic of the allenylidene ligand, shifts to higher wavenumber (from 1959 to 2032 cm −1 ) as a result of oxidation of [ 1 ] + to [ 1 ] 2+ , consistent with a strongly metal-centred redox process and an enhancement in the alkynyl character of the allenylidene ligand following one-electron oxidation. [ABSTRACT FROM AUTHOR]

• Dinitrogen ligand in [Mo(depe) 2 (N 2) 2 ] substitutes chloride in a series of group IV-VI halide compounds. • Formation of heterobimetallic complexes is accompanied by a formal two-electron reduction of N 2. • Structural characterization by sc-XRD of 5 different N 2 -bridged heterobimetallic complexes. • Qualitative bonding analysis focused on the Mo-N-N-M' p orbitals bolster structural similarities and discrepancies. A series of N 2 -bridged (μ-η1:η1-N 2) heterobimetallic complexes were prepared by the reaction of the dinitrogen complex [Mo(depe) 2 (N 2) 2 ] (depe = 1,2-bis(diethylphosphino)ethane) with the group IV-VI high valent metal halides [Cp 2 ZrCl 2 ], NbCl 5 , TaCl 5 , MoCl 5 and WCl 4 via chloride substitution. Compounds [MoCl(depe) 2 (μ-N 2)ZrCp 2 Cl] (1) and [MoCl(depe) 2 (μ-N 2)M'Cl 4 (THF)] (2 – 5 , M' = Nb, Ta, Mo or W) were crystallized from the reaction mixtures. In the case of the reaction with WCl 4 , disproportionation of W(IV) was suspected but not evidenced. Single crystal X-ray diffraction analyses on all compounds allowed a systematic structural study, and the sketching of qualitative molecular orbital diagrams helped discussing the bonding situation and bolster the structural data. [Display omitted] [ABSTRACT FROM AUTHOR]

• Dinuclear [CpRu(CO) 2 ] 2 , [CpMo(CO) 3 ] 2 and [Cp(OC) 2 RuMo(CO) 3 Cp] react with diphenyl dichalcogenides via visible light photocleavage of metal-metal bond • Reaction rate for [CpRu(CO) 2 ]• radical is in the order: PhSSPh >> PhSeSPh > PhSeSePh • Reaction rate for [CpMo(CO) 3 ]• radical in the order: PhSeSePh ∼ PhSeSPh > PhSSPh • Reactions of PhSeSPh with the organometallic radicals favour the formation of CpRu(CO) 2 (SePh) and CpMo(CO) 3 (SPh) The reaction of the dinuclear organometallic complexes [CpRu(CO) 2 ] 2 , [CpMo(CO) 3 ] 2 and [Cp(OC) 2 RuMo(CO) 3 Cp] with diphenyl dichalcogenides proceeded under visible light irradiation, via photocleavage of the metal-metal bond. Measurements of the reaction rates point to a preference of the organoruthenium radical for sulfur, and the organomolybdenum radical for selenium. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermolysis of [Ru 3 (CO) 12 ] with an in-situ generated intermediate, obtained from the reaction of [Cp*MoCl 4 ] and [LiBH 4 .THF], led to the formation of [{Cp*Mo(CO) 2 }(μ 4 -B){Ru(CO) 3 } 3 (μ-H) 2 ], 2 and [{Cp*Mo(CO) 2 } 2 (μ 4 -B){Ru(CO) 3 } 2 (μ-H)], 3 (Cp* = η 5 -C 5 Me 5 ). In a similar fashion, when [Ru 3 (CO) 12 ] was thermalized with [(Cp*Rh) 2 B 2 H 6 ], obtained from a fast metathesis reaction of [Cp*RhCl 2 ] 2 , 4 and [LiBH 4 .THF], yielded a novel heterometallic boride cluster [(Cp*Rh)(μ 6 -B){Ru(CO) 3 } 4 {RuH(CO) 2 }], 5 . Both compounds 2 and 3 can be described as 50-cluster valence electron (cve) hetero-metallic boride clusters, in which the boron atom is in semi-interstitial position of a M 4 -butterfly geometry. Compound 5 contains 86 cluster valence-electrons, in which the boron atom is inside of an octahedral hole composed of one rhodium and five ruthenium atoms. Computational studies on the ground of density functional theory has been undertaken to analyze the bonding of 2 , 3 and 5 . The structural optimization yields geometries in agreement with the structure determinations and computed 11 B chemical shifts accurately reflect the observed shifts. The molecular orbital analysis of them shows that all the valence orbitals of boron have been participated in bonding and therefore provides the “encapsulation” picture of the boron atom. All the compounds have been characterized by IR and 1 H, 11 B, and 13 C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analyses of compounds 2 , 3 and 5 . [ABSTRACT FROM AUTHOR]

Dispersion corrected density functional theory calculations of the metallostannylene complexes [(η 5 -C 5 H 5 )(CO) 3 M(SnC 6 H 3 -2,6-Ar 2 )] ( 1 – 6 ; M = Cr, Mo, W; Ar = Mes, Trip), [(η 5 -C 5 H 5 )(CO) 2 Fe(SnC 6 H 3 -2,6-Dip 2 )] ( 7 ) and [(η 5 -C 5 H 5 )(CO) 2 Fe(SnC 6 H 3 -2,6-Trip 2 )] ( 8 ) and monomeric diaryl stannylenes [Sn(C 6 H 2 -2,6-Mes 2 -4-Cl) 2 ] ( 9 ), [Sn(C 6 H 2 -2,6-Mes 2 -4-SiMe 3 ) 2 ] ( 10 ), [Sn(C 6 H-2,6-Mes 2 -3,5-iPr 2 ) 2 ] ( 11 ), [Sn(C 6 H 3 -2,6-Mes 2 ) 2 ] ( 12 ) and [Sn(C 6 H 3 -2,6-Dip 2 ) 2 ] ( 13 ) (Mes = C 6 H 2 -2,4,6-Me 3 ; Trip = C 6 H 2 -2,4,6- i Pr 3 ; Dip = C 6 H 2 -2,6- i Pr 2 ) have been carried out at the BP86-D3(BJ)/TZ2P/ZORA level of theory. The calculated geometrical parameters of the studied metallostannyles (Power et al., Organometallics 21 (2002) 5622; 30 (2011) 6316) and diaryl stannylenes (Power et al., Organometallics 34 (2015) 2222) are in good agreement with the available experimental values. The bent geometries at tin are consistent with the presence of a divalent Sn(II) center. The M-Sn-C bond angles in metallostannylenes are smaller than C Sn C bond angles in diaryl stannylenes. The lengthening of M − Sn bonds and decrease in M Sn C bond angles are found in the solvent (benzene) phase geometries optimized. The 119 Sn NMR chemical shifts (ppm) have been calculated with the direct implementation of the gauge including atomic orbitals (GIAO) method. The calculated 119 Sn chemical shifts with ZORA spin orbit level in gas phase yield reliable results. While switching from ZORA spin orbit level to ZORA scalar level results 119 Sn upfield shift of ca. 300–400 ppm. Due to greater percentage s character of Sn lone pair in the chromium complexes [(η 5 -C 5 H 5 )(CO) 3 M(SnC 6 H 3 -2,6-Mes 2 )] ( 1 ) and [(η 5 -C 5 H 5 )(CO) 3 M(SnC 6 H 3 -2,6-Trip 2 )] ( 4 ), the upfield 119 Sn NMR chemical shifts are observed. The relationship between computed ( δ calcd ) 119 Sn NMR chemical shifts and 1 / ΔE (LUMO-HOMO)) clearly exhibit a linear trend. The difference between 119 Sn NMR chemical shifts of metallostannylenes ( 1 – 8 ) and diaryl stannylenes ( 9 – 13 ) has been analyzed. The Sn C bonds in diaryl stannylenes are weaker than the Sn C bonds in metallostannylenes. The Sn nuclei are more shielded in diaryl stannylenes than in metallostannylenes. As a consequence, the upfield values of 119 Sn NMR chemical shifts are observed for diaryl stannylenes both experimentally and theoretically. Upfield 119 Sn chemical shifts, which deviate much from the experimental values, are observed for optimized geometries of metallostannylenes in solvent (benzene) phase. The decrease in asymmetric parameter ( η ) causes a downfield 119 Sn NMR chemical shift accompanied by an increase in 119 Sn chemical shift anisotropy. [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 carbonyl-bridged complex [Mo 2 Cp 2 (μ-CPh) (μ-PCy 2 ) (μ-CO)] ( 1 ) reacted with [Fe 2 (CO) 9 ] at room temperature to give the 46-electron trinuclear cluster [FeMo 2 Cp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 5 ] (Mo–Mo = 2.6782(4) Å), and a similar Mo 2 Ru cluster was obtained upon reaction with [Ru 3 (CO) 12 ] under irradiation with visible-UV light (Cp = η 5 -C 5 H 5 ). Compound 1 reacted with [Co 2 (CO) 8 ] at room temperature to give the 60-electron tetrahedral cluster [Co 2 Mo 2 Cp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 7 ], which in solution exits as an equilibrium mixture of two isomers and presumably displays phosphide and carbyne ligands in a cisoid arrangement. This compound evolved thermally to give a third isomer having these ligands arranged in a transoid way (P–Mo–C = 126.3(1) o , Mo–Mo = 2.9612(6) Å). The dicarbonyl complex [Mo 2 Cp 2 (μ-CPh) (μ-PCy 2 ) (CO) 2 ] ( 2 ) reacted with W(CO) 6 under visible-UV light irradiation to give two thermally unstable isomers of the 46-electron trinuclear cluster [Mo 2 WCp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 6 ]. Reaction of 2 with [AuCl(PR 3 )] (R = Me, p-tol, i Pr) in the presence of TlPF 6 gave first the corresponding cationic clusters trans -[AuMo 2 Cp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 2 (PR 3 )]PF 6 , which then evolved thermally to the more stable isomers cis -[AuMo 2 Cp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 2 (PR 3 )]PF 6 (Mo–Mo = 2.810(1) Å for R = i Pr), selectively formed with a syn conformation of the carbyne and Cp ligands, except for the PMe 3 complex. In contrast, reaction of 2 with CuCl led to a cluster of composition [CuMo 2 ClCp 2 (μ 3 -CPh) (μ-PCy 2 ) (CO) 2 ], presumably present as a monomer in solution, but certainly appearing in the solid state as a centrosymmetric dimer held by bridging Cu–Cl–Cu interactions (Mo–Mo = 2.8004(5), Cu–Cl = 2.309(1), 2.409(1) Å). [ABSTRACT FROM AUTHOR]

Phillips CrO x /SiO 2 catalyst is an important catalyst for industrial production of polyethylene. In this work, a Mo-modified Phillips catalyst for ethylene polymerization (defined as CrMo/Si ) was developed. The characterizations of the Phillips catalyst (defined as Cr/Si ) and the CrMo/Si catalyst by temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) showed an obvious interaction between the chromium and molybdenum components on the silica support. The ethylene polymerization performances at different conditions, in terms of H 2 responds, polymerization temperatures, and the copolymerization with 1-hexene were systematically investigated. Although the polymerization activity of the CrMo/Si catalyst was lower, the copolymer presented a higher molecular weight (MW) and a broader molecular weight distribution (MWD). The Mo-modified Phillips catalyst ( CrMo/Si ) exhibited 67% higher 1-hexene incorporation ability as determined by 13 C NMR. Moreover, the short chain branch distribution (SCBD) of the copolymer obtained via the CrMo/Si catalyst was also improved as confirmed by temperature rising elution fractionation (TREF) cross successive self-nucleation and annealing (SSA) methods. The results of TREF and SSA showed that the amount of short chain branches for the copolymer was increased in the high MW part, which would benefit for the long term mechanical property of polyethylene. [ABSTRACT FROM AUTHOR]

Building upon our earlier work on low-boron containing molybdaborane arachno -[Cp*Mo(CO) 2 B 3 H 8 ], 1 we continue to investigate the reactivity of the same system with group 8 metal carbonyl compounds. As a result, thermolysis of arachno - 1 in presence of [Ru 3 (CO) 12 ] led to the formation of neutral heterometallic ketenylidene cluster [Cp*Mo(CO) 2 ( μ -H)Ru 2 (CO) 6 ( μ 3 - ɳ 1 -CCO)], 2 , in which the triply bridged ketenylidene fragment (CCO) is lying perpendicular to the plane of the metal triangle (Ru–Mo–Ru). In addition to the formation of cluster 2 , the reaction also yielded a semi-interstitial boride cluster [Cp*Mo(CO) 2 {Ru(CO) 3 } 4 B], 3 and a known bimetallic cluster [Cp*Mo(CO) 3 ] 2 , 4 in moderate yields. The geometry of 3 can be described as a square pyramidal, in which the boron atom caps the square face formed by three Ru and one Mo atoms respectively. All the new compounds have been characterized by multinuclear NMR spectroscopy, IR spectroscopy and mass spectrometry. In addition to these, the solid state structure of 2 and 3 were unequivocally established by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Room temperature photolysis of [Cp*Mo(CO) 3 Me], 1 with excess of [BH 3 ·THF] led to the isolation of hydrogen-rich arachno -[Cp*Mo(CO) 2 B 3 H 8 ], 2 in good yield. The geometry of arachno - 2 consists of a butterfly core similar to that of 7 skeletal electron pairs tetraborane(10). Further, the metal fragment addition reaction of arachno - 2 with [Fe 2 (CO) 9 ] yielded a nido -[Cp*Mo(CO) 2 B 3 H 6 Fe(CO) 3 ], 3 that plays a pivotal role in bringing a change in the geometry from arachno - 2 to nido - 3 . The reaction of arachno - 2 with [Ru 3 (CO) 12 ], however, yielded known metal carbonyl compound [Cp*Mo(CO) 3 ] 2 , 4 . All the new compounds have been characterized in solution by mass spectrometry, IR, 1 H, 11 B, 13 C NMR spectroscopy and the solid state X-ray structures of 2 and 3 were unequivocally established by X-ray diffraction analysis. Additionally, we have studied the bonding nature of compounds 2 and 3 with the help of density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

A series of allyl complexes of the general formula [Cp'Mo(η 3 -C 3 H 5 )(CO) 2 ], where Cp' = Cp, CpMe, Cp*, Ind, IndMe, IndMe 2 , Flu, and three tungsten analogues, has been prepared and characterized by 1 H, 13 C, and 95 Mo NMR, cyclic voltammetry, and the structure of [IndMo(η 3 -C 3 H 5 )(CO) 2 ] was determined by X-ray single crystal analysis. Two conformers, corresponding to the two extreme orientations of the allyl ligand ( endo and exo ), have been identified in solution by 1 H and 95 Mo NMR for all the complexes, except for [FluMo(η 3 -C 3 H 5 )(CO) 2 ], which only presents an exo conformation in solution. A 95 Mo NMR investigation also shows the influence of electron donor capability of the Cp' ligands on the 95 Mo chemical shifts of the Mo center. He I and He II photoelectron spectra probe the electron richness of the metal center and the electronic structure of the complexes. Cyclic voltammetry studies show one oxidation process, which is only reversible for the Cp derivatives. DFT calculations provided a reliable way to determine ionization energies, and reflected very well the trends of the other properties, from the 95 Mo NMR chemical shifts, to vibration frequencies, and oxidation potentials. [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]

Molybdocene dichloride (Cp 2 MoCl 2 ), a metallocene dichloride currently being evaluated as potential anti-cancer drug, has been intercalated into zirconium phosphate, an inorganic layered nanomaterial. Hydrolysis of the chloride ligands appears to occur, leading to the formation of the monocation species ([Cp 2 Mo(H 2 O)(OH)] + ), which intercalates into the ZrP layers by ion exchange. IR spectroscopy, X-ray powder diffraction (XRPD), UV–Vis spectrophotometry, scanning electron microscopy with energy dispersive X-ray spectroscopy, NMR spectroscopy, and thermogravimetric analysis were used to confirm the presence of the metallocene between the layers of zirconium phosphate. The XRPD data indicates that a new intercalated phase with an expanded interlayer distance of 11.0 Å was obtained; thermogravimetric analysis indicates up to 64% loading in the context of molar ratio (0.64 mol per ZrP formula unit) or 32% exchange capacity. Further evidence for intercalation was obtained from 31 P MAS NMR experiments. IR spectroscopy confirms the presence of the cyclopentadienyl bearing metallocene in the layers. [ABSTRACT FROM AUTHOR]

Reaction of free dineopentyl-benzimidazoline-2-ylidene 1 (ligand: np 2 bimy) with (η 3 -cycloheptatriene)Mo(CO) 3 , molar ratio 3:1, provides the coordinatively unsaturated lateral -(np 2 bimy) 2 Mo(CO) 3 complex 2 . Crystal structure analysis of 2 reveals an almost ideal cis -square pyramidal geometry with tilted coordination of the metal, interplanar angles of the np 2 bimy ligands to the C 4 Mo plane of about 70° and significant bending of the N-heterocyclic carbene rings towards each other. Quantum chemical calculations (B97-D/6-31G(d)[Mo:cc-pVTZ-PP] level of theory) reproduce this peculiar structure and show it to be more stable by 36 kJ/mol than the second energy-minimum structure with trigonal bipyramidal geometry and the carbene ligands in the axial positions. Calculations indicated no significant Mo–C(II) back-bonding or interactions of the empty d-orbital with adjacent p-orbitals of the ligands, implying that the ligand distortions, tilted coordination and the occurrence of a free coordination site are caused by the spatial demand of the N-substituents. [ABSTRACT FROM AUTHOR]

A series of Mo(0) and W(0) carbonyl N-heterocyclic carbene (NHC) complexes containing monodentate NHC ligands with the formulae of M(CO) 4 (NHC) 2 (NHC = IBz = 1,3-dibenzylimidazol-2-ylidene, M = Mo ( 1a ), W ( 2a ); NHC = I n Pr = 1,3-dipropylimidazol-2-ylidene, M = Mo ( 3 ), W ( 4a )) and M(CO) 5 (NHC) (NHC = IBz, M = Mo ( 1b ), W ( 2b ); NHC = I n Pr, M = W ( 4b ); NHC = IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, M = Mo ( 5 ), W ( 6 )) and the complexes containing chelating NHC ligands Mo(CO) 4 (PyNHC) (PyNHC = 3-methyl-1-picolylimidazol-2-ylidene ( 7 )) and Mo(CO) 3 (Py 2 NHC) (Py 2 NHC = 1,3-dipicolylimidazol-2-ylidene ( 8 )) have been synthesized and fully characterized. They show moderate catalytic activities towards cyclooctene epoxidation in the presence of tert -butyl hydroperoxide (TBHP). The stability of Mo–C NHC bond under oxidative condition has been investigated. [ABSTRACT FROM AUTHOR]

The reactivity of cyclopentadienyl and indenyl molybdenum(II) complexes [( η 5 -Cp′)Mo(CO) 2 (NCMe) 2 ][BF 4 ] (Cp′ = Cp, Ind, 1,3-Ph 2 C 9 H 5 ) with a series of planar N , N , N -chelating ligands was scrutinized. The planar N , N , N -chelating ligands give κ 2 -complexes [( η 5 -Cp′)Mo(CO) 2 ( κ 2 - N,N,N L)][BF 4 ] those undergo in particular cases a spontaneous release of carbon monoxide to give [( η 5 -Cp′)Mo(CO)( κ 3 - N,N,N L)][BF 4 ] depending on several factors including the basicity of the tridentate ligand as well as the nature of the starting molybdenum(II) compound. This behaviour strongly contrasts with tripodal ligands those do not affect cis -Mo(CO) 2 moiety even upon tridentate coordination. All structure types, discussed in this work, were elucidated by the spectroscopic measurements as well as by the X-ray crystallography. [ABSTRACT FROM AUTHOR]

Several molybdenum(VI) dioxo complexes have been investigated as catalyst precursors for allylic alcohol epoxidation using mainly hydrogen peroxide as oxidant. All catalysts proved to be efficient and selective for the epoxidation of allylic alcohols provided the olefins were rather electron rich. Indeed, electron poor substrates could be converted selectively into the corresponding unsaturated aldehydes. A chiral dioxomolybdenum complex based on an optically pure tridentate Schiff base ligand was synthesized and characterized. Though that complex provided an efficient epoxidation catalyst for allylic alcohols and olefins, no chiral induction was observed. During the X-ray diffraction analysis, the cooling at 100 K led to the appearance of super-lattice reflections on diffraction patterns reflecting an ordering of the structure. Instead of one organometallic species observed at 298 K, three similar complexes of the same molecular structure could be observed in the asymmetric unit at 100 K. [ABSTRACT FROM AUTHOR]

The hitherto new molybdenum coordination complexes ( η 5 -C 5 HPh 3 PEt 3 )Mo(CO) 3 ( I ), ( η 5 -C 5 HPh 3 PMe 2 Ph)Mo(CO) 3 ( II ) and ( η 5 -C 5 HPh 3 PMePh 2 ) Mo(CO) 3 ( III ) has been synthesized and characterized via substitution reactions of triethylphosphonium triphenylcyclopentadienylide (C 5 HPh 3 PEt 3 ), dimethylphenylphosphonium triphenylcyclopentadienylide (C 5 HPh 3 PMe 2 Ph) and diphenylmethylphosphonium triphenylcyclopentadienylide (C 5 HPh 3 PMePh 2 ) with Mo(CO) 3 (CH 3 CN) 3 respectively as a stable coordination complexes. The structure of compound was characterized on the basis of 1 H NMR, 13 C NMR, 31 P NMR spectroscopies, elemental analyses, and X-ray crystallography. The structures of the free ligands and their molybdenum complexes I , II , and III were compared with the reported analogous compound (C 5 H 4 PMePh 2 ) and its complex ( η 5 -C 5 H 4 PMePh 2 )Mo(CO) 3 . The IR spectrum of complex in which values of ν (CO) and the M−C 5 (centroid) bond lengths showing strong evidences about the effects the electron-donating ability of ligands towards Mo(CO) 3 (CH 3 CN) 3 by the multiple phenyl group of cyclopentadienyl ring. The P–C (1) bond distance of II shorter than that of III indicated that the steric effect of PR 3 moiety is the dominating factor. [ABSTRACT FROM AUTHOR]

The reaction between in situ generated H 2 Se and [Cp*MoO 2 Cl] ( 1 ) produces a mixture of binuclear and trinuclear selenium clusters. New selenide complex [Cp* 2 Mo 2 Se 6 ] ( 2 ) was isolated from CH 2 Cl 2 extracts of the products mixture and characterized by X-ray analysis. This binuclear cluster contains two unprecedented Se 3 4− ligands isoelectronic to I 3 − . Column chromatography of extracts in air produced two bands, from which [Cp* 2 Mo 2 O 2 Se 2 ] ( 3 ) and a new triangular cluster [Cp* 3 Mo 3 Se 4 ][ZnCl 3 (H 2 O)] ( 4 ) were isolated and structurally characterized. The products were characterized by 1 H and 77 Se NMR, ESI–MS, IR and elemental analysis. Quantum-chemical calculations were used to analyze the Mo–Mo bonding and to help identify lines in 77 Se NMR spectra. Crystal and molecular structure of starting [Cp*MoO 2 Cl] was also determined. [ABSTRACT FROM AUTHOR]

A series of molybdenum(0) tetra- and tricarbonyl complexes has been synthesized which are supported by the bi- and tridentate, NHC/phosphine ligands di(1-ethylbenzimidazol-2-ylidene)methane (Benz-CC), 3-(2-diphenylphosphanylethyl)-1-ethylbenzimidazol-2-ylidene (Benz-CP) and 1,3-bis(2-diphenylpho-sphanyl-ethyl)5,6-dimethylbenzimidazol-2-ylidene (DMBenzPCP), respectively. The compounds [Mo(CO) 4 (Benz-CC)] ( 1 ), [Mo(CO) 4 (Benz-CP)] ( 2 ) and fac -[Mo(CO) 3 (DMBenz-PCP)] ( 3 ) are characterized by X-ray structure analysis, vibrational and NMR spectroscopy complemented by DFT calculations. The derived description of the benzimidazol-2-ylidene molybdenum bond is compared to that of the imidazole-based counterparts investigated earlier. The benzimidazole-based ligand systems exhibit a slightly lower activation of the carbonyl ligands, which is mainly explained by a lower σ-donor strength of the benzimidazol-2-ylidene unit. On the other hand there is some evidence for a slightly higher π backbonding capacity of the benzimidazole-based NHC ligands in comparison to their imidazole analogues. [ABSTRACT FROM AUTHOR]

• Synthesis of cationic molybdenum dicarbonyl complexes bearing bipyridine ligands. • Ionic liquid-supported complexes catalyze the isomerization of α-pinene oxide. • The type of ionic liquid and the reaction conditions affect reaction kinetics. • Campholenic aldehyde is the major product formed in up to 95% yield (1 min, 35 °C). • [IndMo(4,4′-dinonyl-2,2′-bipyridine)(CO) 2 ](BF 4) performed very steadily for 3 runs. Campholenic aldehyde (CPA), an important flavor and fragrance intermediate, can be obtained by the Lewis acid-catalyzed isomerization of α-pinene oxide (PinOx), although achieving high yields (>90%) is a difficult challenge due to the high reactivity of the epoxide. In the present work, indenyl-molybdenum(II)-bipyridine complexes [IndMo(bipyR)(CO) 2 ](BF 4) (bipyR = 2,2′-bipyridine (R = H) or 4,4′-disubstituted-2,2′-bipyridine) have been combined with various ionic liquid solvents to develop an efficient process for the selective conversion of PinOx to CPA under mild (35 °C) conditions. Excellent CPA yields (95%) were repeatedly obtained within 1 min reaction time for the easily recyclable catalytic system comprising [IndMo(4,4′-dinonyl-2,2′-bipyridine)(CO) 2 ](BF 4) and choline bis(trifluoromethylsulfonyl)imide. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Compounds [Cp*2M2O5] (M = Mo, W) react with stoichiometric amounts of H2O2 (as a 30% w/w solution in water) and t BuOOH (TBHP, as a 70% w/w solution in decane) in MeCN solution to yield a variety of products as shown by the 1H NMR monitoring of the Cp* resonance. The reaction rate increases in the order W < Mo and TBHP < H2O2. While the total Cp* intensity remains constant when using stoichiometric amounts of oxidant, use of excess oxidant results in the ultimate total Cp* loss. From the decomposed solutions, crystals of [Cp*2Mo6O17] (1), (C5Me5O)[Cp*M6O18] (M = Mo, 2a; W, 2b), and (C5Me5O)2[Mo6O19] (3) were recovered and analyzed by X-ray diffraction. Catalytic cyclooctene epoxidation experiments with ( n Bu4N)2[M6O19] (M = Mo, W) in a 3:1 MeCN/toluene mixture at 55 °C using either aqueous H2O2 or TBHP/decane as oxidant revealed that these are not the active forms of the catalyst which is generated under the same conditions from [Cp*2M2O5], as reported in previous contributions from our group (Chem. Eur. J., 2010, 16, 9572–9584; Eur. J. Inorg. Chem., 2013, 2728–2735). Further catalytic studies using aged [Cp*2Mo2O5]/TBHP and [Cp*2W2O5]/H2O2 solutions show a small loss of activity (<50% in one week) attesting the robustness of the non-organometallic catalytically active species that is generated from the decomposition of [Cp*2M2O5]. These results cast doubts on the role of cyclopentadienyl as a supporting ligand for stable olefin epoxidation catalysts. [Copyright &y& Elsevier]

Abstract: The complex CpMo(CO)3CH2COOH (1) (Cp = η5-C5H5) has been examined as a precatalyst for the epoxidation of cis-cyclooctene and α-pinene using tert-butylhydroperoxide (TBHP) as oxidant. A high turnover frequency of ca. 600 mol molMo −1 h−1 was achieved in the epoxidation of cyclooctene, giving the epoxide as the only reaction product. With α-pinene as substrate, the added-value products α-pinene oxide and campholenic aldehyde were obtained. Two different approaches to facilitate catalyst recovery and reuse were explored: (1) use of an ionic liquid (IL) as solvent, and (2) intercalation of 1 in a Zn,Al layered double hydroxide (LDH) by a direct synthesis (coprecipitation) route. Characterization of the LDH by powder X-ray diffraction, thermogravimetric analysis, FT-IR and 13C CP MAS NMR spectroscopies showed that the CpMo(CO)3CH2COO− anions intercalate in a bilayer arrangement, resulting in an interlayer spacing of 20.7 Å. In the epoxidation of cyclooctene, catalytic activity in the first batch run was very high for the catalyst/IL mixture and moderate for the LDH. Characterization of the LDH after catalysis indicated that nearly complete oxidative decarbonylation of supported complexes had occurred (by reaction with TBHP), resulting in the presence of immobilized oxomolybdenum species. However, catalytic activities for both the recovered LDH and catalyst/IL decreased in consecutive runs, due in part to progressive removal of active species during either the catalytic reaction (for the LDH) or the solvent extraction/work-up (for the catalyst/IL mixture). [Copyright &y& Elsevier]

The compounds MoO2Cl2L (L = 2,2′-bipyridine (bipy) (1); 4,4′-di-tert-butyl-2,2′-bipyridine (di- t Bu-bipy) (2)), [MoO2Cl2(H2O)2]·(diglyme)2 (3), MoO2Cl2 (4), MoO2(CH3)2L (L = bipy (5); di- t Bu-bipy (6)), [MoO3(bipy)] n (7), {[MoO3(bipy)][MoO3(H2O)]} n (8), [Mo8O22(OH)4(di- t Bu-bipy)4] (9) and MoO3 (10) were tested as phosphoester bond hydrolysis promoters in aqueous media. Sodium para-nitrophenylphosphate (pNPP) was used as a model substrate for the phosphoester bond hydrolysis reaction, which was performed at 55 °C, using D2O as solvent and 100 or 10 mol% of the chosen promoter. The progression of all the reactions was monitored by 1H NMR spectroscopy. All studied systems promote phosphoester bond hydrolysis. The best performance was obtained with MoO2Cl2L compounds (1–4) and with the inorganic–organic hybrid {[MoO3(bipy)][MoO3(H2O)]} n (8). The studied compounds originate either homogeneous or solid/liquid biphasic systems. For the biphasic systems (1, 2, 5–9), the solid phase was recovered at the end of the reaction and characterized by FT-IR spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: In the present study a complete series of seven-coordinate neutral halocarbonyl Mo(II) complexes of the type [Mo(PNPMe-Ph)(CO)2X2] (X = I, Br, Cl, F), featuring the new PNP pincer ligand N,N′-bis(diphenylphosphino)-N,N′-methyl-2,6-diaminopyridine (PNPMe-Ph), were prepared and fully characterized. The synthesis of these complexes was accomplished by different methodologies depending on the halide ligands. For X = I and Br, [Mo(PNPMe-Ph)(CO)2I2] and [Mo(PNPMe-Ph)(CO)2Br2] were obtained by reacting [Mo(PNPMe-Ph)(CO)3] with stoichiometric amounts of I2 and Br2, respectively. Alternatively, these complexes were obtained upon treatment of [MoX2(CO)3(CH3CN)2] (X = I, Br) with 1 equiv. of PNPMe-Ph. On the other hand, in the case of X = Cl, [Mo(PNPMe-Ph)(CO)2Cl2] was afforded by the reaction of [Mo(CO)4(μ-Cl)Cl]2 with 1 equiv. of PNPMe-Ph. The equivalent procedure also worked for X = Br. Finally, addition of 1 equiv. of 1-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate to [Mo(PNPMe-Ph)(CO)3] yielded the analogous fluorine complex [Mo(PNPMe-Ph)(CO)2F2]. The modification of the ligand scaffold by introducing a Me group instead of H changed the properties of the PNP-Ph ligand significantly. While in the present case exclusively neutral seven-coordinate complexes of the type [Mo(PNPMe-Ph)(CO)2X2] were obtained, with the parent PNP-Ph ligand, i.e., featuring NH spacers, cationic seven-coordinate complexes of the type [Mo(PNP-Ph)(CO)3X]X were afforded. DFT calculations indicated that the reactions are under thermodynamic control. The structures of representative complexes were determined by X-ray single crystal analyses. [Copyright &y& Elsevier]

Abstract: The organometallic fragment [MoI2(CO)3] was coordinated to magnetic iron oxide nanoparticles of different sizes (average size of 11 and 30 nm) which have been previously coated with a silica shell and grafted with a pyridine derivative ligand. The Mo loading was found to be approximately 0.37 wt-% Mo and 0.57 wt-% Mo, corresponding to 0.150 mmolMo g−1 and 0.230 mmolMo g−1 for materials MNP 30 -Si-inic-Mo and MNP 11 -Si-inic-Mo, respectively. Preparation of these organometallic decorated magnetic nanoparticles was further confirmed by evidence obtained from extensive characterization by powder XRD, SEM/TEM analysis, as well as from data of 57Fe Mössbauer and FTIR spectroscopy. Olefin epoxidation of a variety of substrates promoted by these organometallic nano-hybrid materials using tbhp as oxidant, was performed with very good results. The catalytic studies show that the catalysts yield selectively the desired epoxides of a series of olefins. In addition, these catalysts are found to work under a wide temperature range and over several catalytic cycles without notorious performance loss in most cases. [Copyright &y& Elsevier]

Abstract: The redox properties and reactivity of [Mo(CO)2(η3-allyl)(α-diimine)(NCS)] (α-diimine = bis(2,6-dimethylphenyl)-acenaphthenequinonediimine (2,6-xylyl-BIAN) and 2,2′-bipyridine (bpy)) were studied using cyclic voltammetry and IR/UV–Vis spectroelectrochemistry. [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(NCS)] was shown by X-ray crystallography to have an asymmetric (B-type) conformation. The extended aromatic system of the strong π-acceptor 2,6-xylyl-BIAN ligand stabilises the primary 1e−-reduced radical anion, [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN•−)(NCS)]−, that can be reduced further to give the solvento anion [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(THF)]−. The initial reduction of [Mo(CO)2(η3-allyl)(bpy)(NCS)] in THF at ambient temperature results in the formation of [Mo(CO)2(η3-allyl)(bpy)]2 by reaction of the remaining parent complex with [Mo(CO)2(η3-allyl)(bpy)]− produced by dissociation of NCS− from [Mo(CO)2(η3-allyl)(bpy•−)(NCS)]−. Further reduction of the dimer [Mo(CO)2(η3-allyl)(bpy)]2 restores [Mo(CO)2(η3-allyl)(bpy)]−. In PrCN at 183 K, [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN•−)(NCS)]− converts slowly to 2e−-reduced [Mo(CO)2(η3-allyl)(2,6-xylyl-BIAN)(PrCN)]− and free NCS−. At room temperature, the reduction path in PrCN involves mainly the dimer [Mo(CO)2(η3-allyl)(bpy)]2; however, the detailed course of the reduction within the spectroelectrochemical cell is complicated and involves a mixture of several unassigned products. Finally, it has been shown that the five-coordinate anion [Mo(CO)2(η3-allyl)(bpy)]− promotes in THF reduction of CO2 to CO and formate via the formation of the intermediate [Mo(CO)2(η3-allyl)(bpy)(O2CH)] and its subsequent reduction. [Copyright &y& Elsevier]

Abstract: The following four Cp2M2B n−2H n−2 structure types (M = Mo, W) have been found in the low-energy structures using density functional theory: (1) Flattened oblatocloso deltahedra related to the experimentally known Cp2Re2B n−2H n−2 structures but not as severely flattened with intradeltahedral M–M (M = Mo, W) distances of ∼2.8 to ∼3.2 Å, which are 0.15–0.30 Å less than those in their Tc and Re counterparts; (2) Structures based on closo or isocloso deltahedra with short M M distances (M = Mo, W) of ∼2.4 to ∼2.6 Å along an edge corresponding to deltahedral surface metal–metal triple bonds; (3) Three 11-vertex deltahedral Cp2M2B9H9 structures (M = Mo, W) structures having two non-adjacent degree 6 vertices occupied by the metal atoms; (4) Two 8-vertex Cp2M2B6H6 structures with multiple degree 3 vertices arising from the capping of smaller deltahedra. In many of these structures one or two of the hydrogen atoms bridge M–B or B–B edges of the deltahedron. [Copyright &y& Elsevier]

Abstract: Improved synthetic routes to [FeI(dppe)Cp], and [MoX(dppe)(η7-C7H7)] (X = Br, Cl) are described. [FeI(CO)2Cp] reacts with dppe in refluxing toluene to give multi-gram quantities of [FeI(dppe)Cp], 3 without the need for photochemical activation. The direct thermal reaction of [MoX(CO)2(η7-C7H7)], 4 with dppe is complicated by competition between associative and dissociative substitution processes. Where X = Br, the associative pathway, which features [MoBr(CO)2(dppe)(η3-C7H7)], 5 as an intermediate, yields cationic [Mo(CO)(dppe)(η7-C7H7)]Br, 7 as the major product. However conditions which promote a dissociative mechanism give good yields of [MoX(dppe)(η7-C7H7)], 6 albeit contaminated with small quantities of [Mo(CO)4(dppe)], 8. The separation of 8 from 6 can be effected by chromatography on alumina but this procedure activates 6 to halide exchange with chlorinated solvents as demonstrated by 31P{1H} NMR investigations on [MoBr(dppe)(η7-C7H7)]. [Copyright &y& Elsevier]

The reactions of coordinated phosphorus-donor ligands have previously been used to prepare bimetallic trans-[cis-Mo(CO)4(PPh2NHCH2CH2NCH(o-C6H4)O)2]M (M = Ni(II), Cu(II)) complexes. Similar bimetallic complexes containing trans-tetracarbonyl-bis(phosphinite)molybdenum(0) centers could be even more interesting because they could serve as molecular gyroscopes. In an attempt to prepare such complexes, the three intermediate compounds trans-Mo(CO)4(PPh2Cl)2 (1), trans-Mo(CO)4(PPh2NHCH2CH2NH2)2 (2), and trans-Mo(CO)4(PPh2NHCH2CH2NCH(o-C6H4)OH)2 (3) were successfully synthesized and fully characterized by multinuclear NMR spectroscopy, elemental analysis and X-ray crystallography. However, the reaction of 3 with Ni(OAc)2(H2O)4 yielded a mixture of crude products with the previously reported trans-[cis-Mo(CO)4(PPh2NHCH2CH2NCH(o-C6H4)O)2]Ni being the only product successfully isolated. The cis product was formed due to facile trans–cis isomerization during the coordination of the Ni(II) to 3. To gain more insight into such isomerizations, the trans–cis isomerizations of 2 and 3 have been followed by 31P{1H} NMR spectroscopy. The reactions follow reversible first order kinetics and appear to display intramolecular mechanisms due to the lack of carbonyl substitutions of the phosphinamidite ligands when the isomerizations are performed under CO atmospheres. Eyring analyses performed on the two complexes show that they have nearly identical activation energies (2: ΔH = 10 ± 2 kJ mol−1, ΔS = 39 ± 5 J mol−1 K−1; 3: ΔH = 11 ± 2 kJ mol−1, ΔS = 41 ± 7 J mol−1 K−1). [ABSTRACT FROM AUTHOR]

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]