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Phosphinines, as aromatic heterocycles, usually engage in coordination as η1-P σ-complexes or η6-phosphinine π-complexes. The μ2-P bridging coordination mode is rarely observed. With the aim to study the effect of different electronic configurations of phosphinines on the coordination modes, a series of anionic phosphinin-2-olates and neutral phosphinin-2-ols were prepared with moderate to high yield. Then the coordination chemistry of these two series was studied in detail towards coinage metals (Au(I) and Cu(I)). It is observed that the anionic phosphinin-2-olates possess a higher tendency to take a bridging position between two metal centers compared to the neutral phosphinin-2-ols. Based on these experimental findings bolstered by DFT calculations, some insight is gained on how the unconventional μ2-P phosphinine bridging coordination mode can be made more conventional and used for the synthesis of polynuclear complexes., Chemical Science, 10 (11), ISSN:2041-6520, ISSN:2041-6539

The platinum(II) and palladium(II) complexes [Pt6(SCH2CH2NH2)8]Cl4 and [Pd6(SCH2CH2OH)8 Cl4· 5H2O with mercamine and β-mercaptoethanol, respectively, were synthesized. It was found on the basis of the comparison of IR and X-ray electron spectra of the ligands and complexes, and also of the data of X-ray diffraction analysis that the bidentate coordination of ligands through sulfur and nitrogen atoms is realized in the platinum(II) complex. In the palladium(II) complex β-mercaptoethanol is coordinated in a mixed-mode type. In both complexes sulfur atoms of the ligands occupy a bridging position.

The influence of lithiation process on the HOMO–LUMO gap and the first hyperpolarizability values of corannulene (C20H10) and quadrannulene (C16H8) buckybowls are investigated using density functional theory (DFT) calculations. Lithiation is performed at the bridging position of the C–C bond of benzene rings of quadrannulene and corannulene. The HOMO–LUMO gap of lithiated buckybowls is reduced with respect to pristine ones. The results indicate that the lithiation process causes the remarkable enhancement of the first hyperpolarizability. The time-dependent density functional theory (TD-DFT) calculations are also performed to understand how lithiation affects the first hyperpolarizability values. The present results might be valuable for further theoretical and experimental studies on the electronic and nonlinear optical properties of buckybowl compounds.

Four planar-chiral, enantiomerically pure ferrocene dibromides (3R1R2; [(CHR1R2)BrH3C5]2Fe) equipped with two CHR1R2 groups in α position to bromine were synthesized. From the four C2 symmetrical species, two are already known [CHR1R2 = CHMe2 (3MeMe), CHEt2 (3EtEt)] and two are new compounds [CHR1R2 = R-CHEtMe (3EtMe), S-CHMeEt (3MeEt)]. The dibromides 3R1R2 were in situ converted into dilithio ferrocene derivatives and reacted with Cl2BNiPr2 resulting in mixtures of bora[1]ferrocenophanes (4R1R2) and 1,1′-bis(boryl)ferrocenes (5R1R2). The aim of this investigation was to test the hypothesis that the alkyl group that is oriented approximately perpendicular to the Cp ring, i.e., R2, affects the outcome of the salt-metathesis reaction. The obtained product ratios 4R1R2:5R1R2 were determined by 1H NMR spectroscopy and revealed that systems with the same R2 group gave similar 4R1R2:5R1R2 ratios (1.0:0.51 and 1.0:0.49 for R2 = Me; 1.0:0.30 and 1.0:0.27 for R2 = Et), confirming the hypothesis. Shown by DFT calc...

The incommensurate modulated crystal structure of Bi2.27Sr1.73CuO6 + δ(2201) phase [a= 5.3874 (5),b= 5.3869 (4),c= 24.579 (3) Å; β = 90.01 (1)°,q= 0.2105 (3)a* + 0.538 (4)c*,Z= 4, the (3 + 1)-dimensional monoclinicA2/a(α0γ) group] has been refined withR= 0.041,wR= 0.052 from X-ray single-crystal data including up to third-order satellite reflections. The same structure has also been considered as incommensurate composite witha2= 2.437,b2= 5.387,c2= 24.614, β2= 93.06,q2= 0.4524a2*−0.243c2*and the (3 + 1)-dimensionalA2/m(α0γ)0sgroup for the second component. Both approaches give quite similar results. The structure possesses oxygen disorder in the oxygen-rich region of the BiO layer. An extra O atom is determined in the bridging position shifted ∼ 0.6 Å from BiO towards the SrO layer. Its presence is the cause of the tremendous increase of the bismuthU11atomic displacement parameter in ∼ 20% of the unit cells (t= −0.05–0.15). Vacancies are determined in the oxygen site of the SrO layer, which may result in the oxygen content variation with annealing at different oxygen pressures. The total refined oxygen content 6.18 (1) corresponds to the results of chemical analysis.

Metallocenophanes with one or multiple sandwich moieties and at least one group 13 element in bridging position are reviewed. The majority of this review summarizes publications concerned with strained sandwich compounds and their application as monomers for metal-containing polymers. Publications up to early 2015 are included.

Ratiometric sensors generally couple binding events or chemical reactions at a distal site to changes in the fluorescence of a core fluorophore scaffold. However, such approaches are often hindered by spectral overlap of the product and reactant species. We provide a strategy to design ratiometric sensors that display dramatic spectral shifts by leveraging the chemoselective reactivity of novel functional groups inserted within fluorophore scaffolds. As a proof-of-principle, fluorophores containing a borinate (RF620) or silanediol (SiOH2R) functionality at the bridging position of the xanthene ring system are developed as endogenous H2O2 sensors. Both these fluorophores display far-red to near-infrared excitation and emission prior to reaction. Upon oxidation by H2O2 both sensors are chemically converted to tetramethylrhodamine, producing significant (≥66 nm) blue-shifts in excitation and emission maxima. This work provides a new concept for the development of ratiometric probes.

Metallocenophanes with one or multiple sandwich moieties and at least one group 13 element in bridging position are reviewed. The majority of this review summarizes publications concerned with strained sandwich compounds and their application as monomers for metal-containing polymers. Publications up to early 2015 are included.

The ditopic tris(2-mercaptoimidazol-1-yl)borate ligand K2[(mtEt)3B–B(mtEt)3] cannot be prepared from B2(NMe2)4/4 HmtEt/2 KmtEt, because the stable intramolecular diadduct (mtEt)B(μ-mtEt)2B(mtEt) is generated instead (HmtEt = 2-mercapto-1-ethylimidazole). Introduction of a meta- or para-phenylene spacer between the two boron atoms precludes the 2-mercaptoimidazol-1-yl groups from adopting a bridging position so that the potassium salts K2[(mtEt)3B-(m-C6H4)-B(mtEt)3] and K2[(mtEt)3B-(p-C6H4)-B(mtEt)3] become readily accessible. These ligands react with [(p-cym)RuCl2]2 to give the dinuclear RuII complexes [(p-cym)Ru(mtEt)3B-(m-C6H4)-B(mtEt)3Ru(p-cym)]Cl2 and [(p-cym)Ru(mtEt)3B-(p-C6H4)-B(mtEt)3Ru(p-cym)]Cl2 (p-cym = p-cymene). After the exchange of the Cl− counterions for [PF6]−, both complexes have been crystallized and structurally characterized by X-ray diffraction.

Bis(cyclopentadienyl)aluminum and -gallium species of the type (Pytsi)ECp2 [E = Al (2a), Ga (2b); Pytsi = C(SiMe3)2SiMe2(2-C5H4N)] have been prepared from NaCp and respective dichlorides (Pytsi)ECl2 in isolated yields of 65% (2a) and 83% (2b). In addition to applying standard methods of characterization (NMR spectroscopy, CHN analysis, and MS), the molecular structures of both compounds were solved by single-crystal X-ray crystallography. Reactions between 2a or 2b with Zr(NMe2)4 in benzene, followed by addition of an excess of ClSiMe3, gave the first ansa-zirconocene dichlorides with aluminum (4a) or gallium (4b) in bridging position. The gallium compound 4b was isolated in a yield of 40% and characterized by NMR spectroscopy, CHN analysis, and mass spectrometry. The aluminum species 4a could not be obtained in an analytically pure form; it was characterized by NMR spectroscopy, and its molecular structure was determined by single-crystal X-ray analysis. The angle between the two planes of the Cp ligands...

The syntheses and magnetic properties are reported for a series of copper(II) complexes prepared from a pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoylhydrazone) (H3L). These complexes incorporate different exogenous ions (X−) into a bridging position to form copper(II) binuclear complexes of the formula [Cu2(H2L)X]2+, where X− = Br−(1), Cl−(2), HO−(3), C2H5O−(4) and C3H3N−2(5). The complexes have been characterized with variable temperature magnetic susceptibility (4.2–300 K) and the observed data were fit to those from a modified Bleaney-Bowen equation by least-squares method, giving the exchange integral 2J = -6.2 cm−1 for 1, -76.4 cm−1 for 2, -241.9 cm−1 for 3, -231.1 cm−1 for 4 and -343.8 cm−1 for 5. This suggested that there is an antiferromagnetic interaction between the Cu(II) ions and the sequence of the effect of some exogenous bridging Uganda on magnetic coupling is corresponding to that in spectrochemical series.

The paramagnetic triple-decker complexes [(Cp*Ru) 2 {μ-(CMe) 3 (BCl)(BMe))] (3b) and [(Cp*Ru) 2 {μ-(CMe) 3 (BCl) 2 }] (3c) are formed by refluxing a mixture of [Cp*RuCl] 4 and pentamethyl-2,3-dihydro-1,3-diborole in thf. In CH 2 Cl 2 under air complex 3b slowly looses a hydrogen atom with formation of the diamagnetic triple-decker [(Cp*Ru) 2 {μ-η 5 :η 6 -(CMe) 3 -(BCl)(BCH 2 )}] (4b) with the unsymmetrical dihydrodiborafulvene derivative in a bridging position. The analogous complex [(Cp*Ru) 2 {μ.η 5 :η 6 -(CMe) 3 (BMe)-(BCH 2 )}] (4a) is obtained by interaction of HCl with the triple-decker [(Cp*Ru) 2 -{μ-(CMe) 3 (BMe) 2 }] (3a). According to calculations, complexes 4a and 4b have an almost non-distorted triple-decker arrangement with a strong bending of the B=CH 2 group toward one of the Ru atoms. For the formation of 3b and 3c the chloro-containing sandwich complexes [Cp*Ru{η 5 -(CMe) 3 -(BCl)(BR 1 )}] (2b,c; R 1 = Me, Cl) are proposed as intermediates. The constitutions of the complexes are derived from NMR, MS and DFT data, and the molecular structure of 3b is confirmed by an X-ray diffraction analysis.

The heteroleptic sandwich complex [Cr(eta(5)-C5H5)(eta(7)-C7H7)] (trochrocene) was prepared by subsequent treatment of CrCl3 with NaCp and Mg in the presence of cycloheptatriene in yields of 40%. Selective dimetalation employing tBuLi/tmeda (N, N, N', N'-tetramethylethylenediamine) afforded the highly reactive species [Cr(eta(5)-C5H4Li)(eta(7)-C7H6Li)] x tmeda. An X-ray crystal-structure determination of its thf solvate revealed a symmetrical, dimeric composition in the solid state, that is, a formula of [Cr(eta(5)-C5H4Li)(eta(7)-C7H6Li)]2 x (thf)8, where the C5H4 moieties of both units are connected by two bridging lithium atoms. Addition of different element dihalides to the dilithio precursor facilitated the isolation of ansa complexes with boron and germanium in the bridging position. Structural characterization by X-ray diffraction studies on [Cr(eta(5)-C5H4)-BN(SiMe3)2-(eta(7)-C7H6)] and [Cr(eta(5)-C5H4)-GeMe2-(eta(7)-C7H6)] emphasized the strained character with tilt angles of 23.87(13) degrees and 15.07(17) degrees , respectively. In contrast, the isolation of the appropriate [1]stannatrochrocenophane failed because of the thermal lability of the resulting product. However, the corresponding 1,1'-disubstitued derivatives [Cr(eta(5)-C5H4R)(eta(7)-C7H6R)] (R = B(Cl)NiPr2, SiMe3, GeMe3, SnMe3) were obtained by reverse addition of the dilithio precursor to an excess of the element (di)halide. The unstrained nature was proven by a crystal structure analysis of the 1,1'-diborylated species. The electronic structure of these substituted trochrocene derivatives, as well as of the [2]bora and [n]sila congeners (n = 1, 2), was investigated by means of UV-vis spectroscopy and DFT methods. As a consequence of the strong electronic influence of the B-N pi-system on the LUMOs, the UV-vis studies revealed a complementary correlation of the lowest energy band maxima as a function of molecular distortion for the boron containing species on the one hand, and the boron-free compounds on the other hand. These trends were reproduced fairly well by time dependent DFT calculations.

DFT calculations with the B3LYP functional are carried out on the systems [Cp(PH3)Ir(SiHR2)]+ and [Cp(PH3)Ir(SiR3)]+ (Cp = C5H5, R = H, CH3, SiH3, Cl), which are representative examples of experimental complexes where the silylene ligand can exist. Geometry optimization for the different systems gives a large variety of structures, including the conventional silyl and hydrido silylene isomers, but also other less usual bridged structures, with a variety of groups taking a bridging position. Analysis of the large amount of data, together with those previously reported for [(dhpe)Pt(SiHR2)]+ and [(dhpe)Pt(SiR3)]+ (dhpe = H2P−CH2−CH2−PH2), leads to a better understanding of the general factors governing the relative stabilities of the possible isomeric forms.

Tishchenko reaction of benzaldehyde was carried out over the MgO whose surface O atoms were enriched with 18 O to examine whether the surface O atoms of MgO are incorporated into the product and reactant. The surface lattice 18 O atoms were incorporated in both the product and reactant. The 18 O concentration was significantly higher for the product than for the reactant. In addition, the 18 O in the product ester was located not only in the carbonyl group (C O) but also in the bridging position (C O C); 18 O exchange between benzaldehyde and MgO surface occurred not only in the adsorption–desorption of benzaldehyde, but also in the dimerization process. The oxygen exchange results in the migration of active sites of coordinative unsaturated site (CUS) over the surface of MgO catalyst during the reaction.

We present transmission electron beam identification of C 60 -based polymeric chains in the mixture between Co and C 60 simultaneously deposited on (0 0 1) NaCl at room temperature. Estimation of intrachain distances taken from the direct image suggests bridging position of Co atoms between buckyballs. The chains tend to be coupled due to Coulomb interaction between the charged units of the polymers. We have confirmed the charge transfer between Co and C 60 detecting 0.6 eV upward shift of C 60 LUMO-derived peak in the electron-energy-loss spectrum of mixture. The systematic shifts of energy-loss σ ∗ peaks imply distortion of C 60 cages belonging to the polymeric chains.

The synthesis and structure of neutral and cationic aluminum compounds equipped with the intramolecular donating C(SiMe3)2SiMe2(2-C5H4N) ligand denoted by Pytsi is described. The compounds (Pytsi)AlMe2 (1), (Pytsi)AlEt2 (2), [(Pytsi)AlMe]+[MeB(C6F5)3]- (3), and [(Pytsi)AlMe(thf)]+[MeB(C6F5)3]- (3·thf) have been synthesized and characterized by standard methods, and the molecular structures of 1, 2, and 3 have been determined by single-crystal X-ray analyses. Compound 3 was obtained by an addition of 1 equiv of B(C6F5)3 to the dimethyl species 1. The salt-like title compound 3 shows a methyl group in a bridging position between Al and B atoms consisting of a long Al−C distance of 2.380(2) A and a B−C bond length of 1.681(3) A.

On the basis of our previous results with aluminum, we herein report the synthesis of the first gallium-bridged [1]ferrocenophane. The attempt to synthesize the respective indium compound resulted in an unusual ferrocenophane containing an In−(μ-Cl)2−In group in the bridging position. All compounds have been characterized by NMR spectroscopy and single-crystal X-ray structural determination.

The molecular structure and thermochemical stability of mono to hexalithiated [3]-prismanes has been investigated by DFT and G3 methods, respectively. Relative isomer stabilities, standard enthalpies of formation and strain energies are discussed and compared. Our results suggest that in lithioprismanes (as in the isomeric lithiobenzenes), Li atom prefers to be in a bridging position along the CC edge rather than to occupy a vertex substitution site. We have estimated the energy stabilization due to bridging and have also studied singlet–triplet energy gaps for the title molecules in order to establish the nature of the ground electronic state.

Metathetical reactions of [Rh2Cl2(μ-CPh2)2(μ-SbiPr3)] 1 with NaBr and NaI afforded the corresponding di-nuclear complexes [Rh2X2(μ-CPh2)2(μ-SbiPr3)] (X = Br 2, I 3) in practically quantitative yields. Analogous displacement reactions of 1 with equimolar amounts of the sodium salts of acetylacetone (acacH), trifluoracetylacetone (acac-f3-H) and dipivaloylmethane (dpmH) led to the formation of the unsymmetrical rhodium(I) compounds [Rh2(X)Cl(μ-CPh2)2(μ-SbiPr3)] (X = acac 4, acac-f35, dpm 6). From 1 and excess of Na(acac) and Na(dpm), the symmetrical complexes [Rh2X2(μ-CPh2)2(μ-SbiPr3)] (X = acac 7, dpm 8) were formed. Treatment of 7 with acetic acid and trifluoracetic acid in the molar ratio of 1 ∶ 1 gave the unsymmetrical compounds [Rh2X(acac)(μ-CPh2)2(μ-SbiPr3)] (X = CF3CO29, CH3CO210), while with an excess of CR3CO2H the symmetrical complexes [Rh2(κ2-O2CR3)2(μ-CPh2)2(μ-SbiPr3)] (R = F 11, H 12) were obtained. The X-ray crystal structure analysis of 12 revealed that analogously to 1 the stibine ligand occupies a symmetrical bridging position. The reactions of 1, 4 and 7 with SbEt3 and Sb(CH2Ph)3 led to bridge-ligand exchange and gave the di-nuclear compounds [Rh2(acac)Cl(μ-CPh2)2(μ-SbEt3)] 13 and [Rh2X(X′)(μ-CPh2)2{μ-Sb(CH2Ph)3}] (X = X′ = Cl 14, X = Cl, X′ = acac 15, X = X′ = acac 16) without cleavage of the [Rh2(μ-CPh2)2] core fragment.

Triple-decker cationic complexes with a central pentaphospholyl (pentaphosphacyclopentadienyl) ligand [Cp*M(μ-η:η-P5)M′(η-C5R5)]+ (3b: M = M′ = Fe, R = Me; 4a: M = Ru, M′ = Fe, R = H; 4b: M = Fe, M′ = Ru, R = H; 4c: M = Fe, M′ = Ru, R = Me; 5a: M = M′ = Ru, R = H; 5b: M = M′ = Ru, R = Me) were synthesized by exploitation of the stacking reactions of pentaphosphametallocenes Cp*M(η-P5) (1: M = Fe; 2: M = Ru) with half-sandwich fragments [(η-C5R5)M′]+. They were isolated as salts with BF4− or PF6− anions, and the structures of 4aPF6 and 5bPF6 were determined by X-ray diffraction. Triple-decker complexes with a central pentaphospholyl ligand are less reactive in nucleophilic degradation reactions than analogous complexes with C4Me4P and Cp* ligands in the bridging position. Only 4a and the previously known analogue 3a (M = M′ = Fe, R = H), containing the CpFe fragment, are nucleophilically destroyed by MeCN and NaI. The electrochemical properties of 2, 3a, 3b, 4a−c, 5a and 5b and the related cobalt-containing complexes [(η-C4Me4)Co(μ-η:η-P5)MCp*]+ (6: M = Fe; 7: M = Ru) were investigated. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The hydride complex K[(η5-C5H5)Mn(CO)2H] reacted with a range of dihalo(organyl)boranes X2BR (X = Cl, Br; R = tBu,Mes, Ferrocenyl) to give the corresponding borane complexes[(η5-C5H5)Mn(CO)2(HB(X)R)]., The presence of a hydride in bridging position between manganese and boron was deduced from 11B decoupled 1H NMR spectra. Additionally, the structure of the tert-butyl borane complex was confirmed by single-crystal X-ray diffraction.

The reaction of [Ru3(CO)12] with (SPR2)2NH produced, initially, [(μ2-H)Ru3(μ3-S){μ2-S,S,P′-(SPPh2)(PPh2)N}(CO)8 and [(μ2-H)Ru3{μ2-S,S,P′-(SPPh2)(PPh2)N}(CO)9] in which for both compounds one of the PS bonds of the ligand has been broken while the other PS group is bonded through the sulfur atom to two ruthenium atoms. In one of the compounds described, the lost sulfur atom moves to a triply bridging position bonded to the triangle of metal atoms. In the second compound, the sulfur atom is lost.

Synthesis of a new type of dinucleoside monophosphate analogue with the 3′–5′ H-phosphonamidate internucleoside linkage, namely thymidin-3′-yl N(thymidin-5′-yl)-H-phosphonamidate 4, was achieved via the reaction of a suitably protected nucleoside aryl H-phosphonate with a 5′-amino-5′-deoxythymidine derivative. The usefulness of 4 as an intermediate for the preparation of various nucleotide analogues was assessed by converting it into the corresponding dinucleoside phosphoramidate and dinucleoside phosphoramidothioate derivatives bearing the PN bond in the bridging position of the phosphoramidate linkage.

The results of our recent studies devoted to the synthesis of cationic triple-decker complexes are summarized. The stacking reactions of cationic metallofragments with sand-with compounds can be used as a general method for the synthesis of these complexes. This method was used for the preparation of 30- and 34-electron cationic triple-decker complexes containing cyclopentadienyl and pentaphospholyl ligands in the bridging position and carbocycles CnHn (n=4–7) and carboranes as terminal ligands.

To improve the activity of dirhodium complexes in thecatalytic reactions or biological reactions, a variety ofligands can be employed not only at the axial position butalso at the bridging position of dirhodium complexes. Sinceligands at either bridging or axial positions vary the electronicand steric properties of dirhodium complexes, investigationson appropriate ligands through the electrochemical analysishave been demanded. The electrochemical analysis ofdirhodium complexes bearing electronically different ligandshas been reported to account for the different catalyticactivity of dirhodium complexes.

The reaction of a mixture of cis-3,7,11-trimethyl-1,5,9-trithiacyclododecane, cis-Me312S3, 1 and trans-3,7,11-trimethyl-l,5,9-trithiacyclododecane, trans-Me312S3, 2, with Ru6(CO)17(μ 6-C), 3, yielded three new cluster compounds Ru6(CO)13(μ-η3-cis-SCH2CHMe(CH2SCH2CHMe)2CH2)(μ 6-C) 4, and two isomers of Ru6(CO)13(μ-η3-cis-SCH2CHMe(CH2SCH2CHMe)2CH2)(μ 6-C) 5a and 5b. The molecular structures of 4 and 5b were established by single crystal X-ray diffraction analyses. In both complexes, the macrocycles have adopted tridentate coordination with one of the sulfur atoms in a bridging position. Two carbonyl ligands occupy bridging positions in each compound. Crystal Data for 4·Me2CO: space group=P21/n, a=11.295(1) A, b=17.547(3) A, c=20.318(3) A, β=93.71(1)°, Z=4, 2900 reflections, R=0.025. Crystal Data for 5b·1.5 C6H6: space group=Pbca, a=31.8900(8) A, b=23.4330(6) A, c=21.6240(4) A, Z=16, 12163 reflections, R=0.040.

Three edge-sharing bioctahedral dimolybdenum(III, III) compounds (PPh4)2[Mo2(OAc)2Cl6] (1), (PPh4)2[Mo2(O2CPh)2Cl6] 2CH3CN (2) and (PPh4)2[Mo2(OAc)4Cl4]·2CH3CN (3) have been synthesized and characterized by X-ray crystallography. All three compounds can be synthesized either by an oxidative addition of Cl2 to their corresponding Mo(II, II) compounds or by reactions of Mo2Cl6(THF)3 with the corresponding carboxylate salts. In the crystal, the bridging position of compound 3 is disordered, occupied by either Cl− or μ, η1-OAc− groups, due to the inclusion of [Mo2(OAc)3Cl5]2 anions. Crystallographic data are as follow: 1, triclinic P 1 with a = 9.004(2), b = 12.499(2), c = 12.863(2) A , α = 107.28(2), β = 105.81(2), γ = 99.72(2)°, V = 1279.9(4) A 3 , Z = 1, R = 0.047, wR2 = 0.128 ; 2, triclinic P 1 with a = 11.3756(9), b = 13.4730(7), c = 10.9611(7) A , α = 102.398(5), β = 102.509(6), γ = 84.205(6)°, V = 1599.2(2) A 3 , Z = 1, R = 0.043, wR2 = 0.120 ; 3, triclinic P 1 with a = 9.9874(7), b = 12.452(3), c = 13.071(4), α = 78.06(3), β = 71.30(1), γ = 76.15(1)°, V = 1479.9(6) A 3 , Z = 1, R = 0.050, wR2 = 0.112 .

The reaction of [B 9 H 13 (SMe 2 )] with primary amines NH 2 R to give eight-boron cluster species [(RH 2 N)B 8 H 11 NHR] is not limited to the case where R = ethyl. We find that the n-butyl, isopropyl and tert-butyl analogues are also readily formed. The structural type is illustrated by a single-crystal X-ray diffraction analysis on the isopropyl member of the family. The reaction proceeds stepwise, via an initial ligand exchange on [B 9 H 13 (SMe 2 )] to give [B 9 H 13 (NH 2 R)], as confirmed by treatment of [B 9 H 13 (SMe 2 )] with NH 2 Bu t to give [B 9 H 13 (NH 2 Bu t )] followed by treatment with Pr i H 2 N to give the mixed species [(Pr i H 2 N)B 8 H 11 NHBu t ], also confirmed by single-crystal X-ray work, and showing that the amine on the starting arachno-{B 9 H 13 } residue is the one that finishes in the more intimately bound bridging position.

The structure of the title compound, bis(μ-ferrocene-1,1′-diyl)­bis­[chloro(N,N,N′N′-tetra­methyl­ethyl­enedi­amine)­aluminium], [Al2Fe2Cl2(C5H4)4(C6H16N2)2], possesses a center of inversion and an anti conformation. Bound to each Al atom in the bridging position are one Cl atom and one mol­ecule of N,N,N′N′-tetra­methyl­ethyl­enedi­amine (TMEDA). The angle between the least-squares planes of the two cyclo­penta­dienyl (Cp) ligands is 3.6 (3)°. The five C atoms in the Cp rings are staggered on average at an angle of 10.3 (5)°.

The first example of a [1]ferrocenophane with a heavier group 13 element in the bridging position is described. The [1]aluminaferrocenophane, with the aluminum atom equipped with a bulky and intramolecularly stabilizing ligand, has been synthesized and structurally characterized by NMR spectroscopy and single-crystal X-ray analysis.

[Rh(μ-O2CCH3)(C2H4)2]2 (3) and analogous carboxylatobis-(olefin)rhodium(I) complexes [Rh(μ-O2CR)(olefin)2]2 (4–6) were almost quantitatively prepared under heterogeneous conditions from [RhCl(C8H14)2]2 (1) or [RhCl(C2H4)2]2 (2) and CH3CO2Na · 3 H2O or RCO2H/NaOH, respectively. The X-ray crystal structure analysis of 3 confirmed the bridging position of the acetato ligands. The synthesis of [Ir(μ-O2CCH3)(C2H4)2]2 (10) was carried out similarly by using [IrCl(C2H4)2]2 (8) and CH3CO2Na · 3 H2O as starting materials. The monoethene complex trans-[Ir(η1-O2CCH3)(C2H4)-(PiPr3)2] (11) was obtained from 10 and PiPr3; it reacted with H2 and HCCPh by oxidative addition to give [IrH2(η2-O2CCH3)(PiPr3)2] (12) and [IrH(CCPh)(η2-O2CCH3)(PiPr3)2] (14), respectively. Compound 12 was also prepared from [IrH2Cl(PiPr3)2] (13) and CH3CO2Na · 3 H2O. The new bis-(ethene)complexes 3, [Rh(μ-O2CC6H5)(C2H4)2]2 (6) and 10 are catalytically less active than 2 in the reaction of C2H4 and Ph2CN2 and gave as C–C coupling product not only 1,1-diphenylpropene (16) but also mixtures of 16 and 1,1-diphenylcyclopropane (17) in different ratios.

The reaction of the dianion [Pt3Ru6(CO)21(μ-H)2]2-, generated in situ by the deprotonation of [Pt3Ru6(CO)21(μ-H)3(μ3-H)], 1, with [Cp*Ir(NCMe)3]2+ and HgI2, has yielded two new higher nuclearity cluster complexes Pt3Ru6(CO)21(μ3-IrCp*)(μ3-H)2, 5, and [NBu4][Pt3Ru6(CO)21(μ3-HgI)(μ3-H)2], 6, in the yields 15% and 35%, respectively. Both compounds were characterized by single-crystal X-ray diffraction analysis. They both contain layer segregated triangular Pt3 and Ru3 groupings stacked one upon the other with the Pt3 group in the center. The heterometal atom occupies a triply bridging position across one of the Ru2Pt triangles. The hydride ligands have adopted triply bridging positions on the two Ru3 triangles.

The solution conformation of C-glycosides 3 and 4 , presenting a hydroxyl group at the bridging position, has been determined by NMR and MM3 ∗ calculations. The conformation of 3 is similar to that of C-lactose, while that of 4 is rather different and shows a significant contribution of a conformer with a gauche disposition between C1′-O5′ and C1′–C2′ bonds.

Rietveld crystal structure refinements have been carried out on the X-ray powder patterns of synthetic N-melilite, Y 2 Si 3 N 4 O 3 , and J-phase, Y 4 Si 2 O 7 N 2 . The melilite structure of Y 2 Si 3 N 4 O 3 is confirmed, in which sheets containing Si 2 O 7 double tetrahedra are linked by Y polyhedra in which two of the eight Y-O contacts are significantly longer (2.78A). The present data were unable to furnish unambiguous details of O/N ordering in either N-melilite or J-phase. The structure of J-phase contains either Si 2 O 5 N 2 or Si 2 O 6 N ditetrahedral units containing N in the bridging position and arranged lengthwise along the a -axis. These units are linked by Y polyhedra. Of the four distinguishable Y sites, three have seven contacts with O and N atoms within 2.8A. One of these sites also has one longer O/N contact at 2.92A. The fourth Y site is in 6-fold coordination.

Detailed redox titrations monitored by EPR and UV-visible spectroscopies have been carried out on the dimeric ferredoxins I and II from Desulfovibrio vulgaris Miyazaki. Ferredoxin II contains a unique [4Fe-4S] cluster per subunit characterized by a midpoint potential of −417 mV at 24°C. The enthalpic and entropic contributions to the redox free energy variation of this cluster have been determined from the temperature dependence of the midpoint potential and compared to the data reported for other iron-sulfur proteins. The molecular arrangement of the two subunits is such that two [4Fe-4S] 1+ clusters are magnetically coupled in the fully reduced state of the protein. Ferredoxin I contains one [3Fe-4S] and one [4Fe-4S] cluster per subunit, whose spectral and redox properties are very similar to those of the same clusters in ferredoxin III from Desulfovibrio africanus . The strong heterogeneity in the redox properties of the [3Fe-4S] center supports a bridging position between the N-terminal and C-terminal parts of the protein.

The Lewis acids RBH2 are added to the basis B-B bond of tri-tert-butylazadiboriridine, NB2tBu3 (1a), to give 5-alkyl-1,2,3-tri-tert-butyl-1-aza-nido-tetraboranes of type 3 (two endo-H atoms at B5) or type 4 (one H atom in a B2–B5 bridging position, one exo-H atom at B5), either as a mixture of 3 and 4 (3, 4b–d: R Me, tBu, CMe2iPr) or with the isomer 4 in high excess (4e, f: R Ph, sBu). The reaction of dialkylboranes R2BH with 1a yields 5,5-dialkyl-1,2,3-tri-tert-butyl-1-aza-nido-tetraboranes of type 4 (one H atom in a B2-B5 bridging position; 4g, h: R2 Et2, cycloocta-1,5-diyl). In boiling THF, trialkylboranes BR3 transform 1a into NB2tBu2R which, expectedly, dimerizes spontaneously to give a dialkyltetra-tert-butyl-2,5-diaza-nido-hexaborane of type 2 (2a, b: R Me, Et). The products of the addition of aminoboranes H2BNRR' to 1a are identified as alkyl derivatives of 2,5-diaza-arachno-pentaborane, N2B3tH2tBu3RR' (5a–d, R/R' = H/Pr, H/tBu, Me/Me, Et/Et). The aminoborane H2B NiPr2 with a sterically more demanding amino group hydroborates the B-B bond of 1a to give the acyclic product iPr2NBH-B(tBu)-N(tBu)B(tBu)H (6). In contrast to the B atoms, the N atoms in the electron-deficient cluster skeletons of 2–5 need not take part in (3c,2e) bonds of the s type. The molecular structures of 4c, 5d, and 6 are confirmed by X-ray structural analyses.

In the centrosymmetric molecular structure of the title compound [Pt2(C6H14P)2H2(C9H21P)2], each PtII atom is bound on one side to a phosphane ligand (PiPr3) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands (μ-PiPr2), which engage a bridging position between the two PtII atoms, forming a distorted square-planar structure motif. The Pt...Pt distance is 3.6755 (2) Å. A comparable molecular structure was observed for bis(μ-di-tert-butylphosphanido)bis[hydrido(triethylphosphane)platinum(II)] [Itazaki et al. (2004). Organometallics, 23, 1610–1621].

We report the selective activation of carbon-fluorine bonds in trifluoroethylene using the diiridium complex [Ir(2)(CH(3))(CO)(2)(dppm)(2)][OTf] (1). Coordination of trifluoroethylene in a bridging position between the two metals in 1 results in facile fluoride ion loss in three different ways. Attack by strong fluorophiles such as Me(3)SiOTf and HOTf results in F(-) removal from one of the geminal fluorines to give the cis-difluorovinyl-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-κ(1):η(2)-C(F)═CFH)(dppm)(2)][OTf]. A second activation can also be accomplished by addition of excess Me(3)SiOTf to give the fluorovinylidene-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-C(2)FH)(dppm)(2)][OTf](2). Interestingly, activation of the trifluoroethylene-bridged precursor by water also occurs, yielding [Ir(2)(CH(3))(CO)(2)(κ(1)-C(H)═CF(2))(μ-OH)(dppm)(2)][OTf], in which the lone vicinal fluorine is removed, leaving a geminal arrangement of fluorines in the product. A [1,2]-fluoride shift can also be induced in the trifluoroethylene-bridged precursor upon the addition of CO to give the 2,2,2-trifluoroethylidene-bridged product [Ir(2)(CH(3))(CO)(3)(μ-C(H)CF(3))(dppm)(2)][CF(3)SO(3)]. Addition of hydrogen to the cis-difluorovinyl-bridged product results in the quantitative elimination of cis-difluoroethylene, while its reaction with CO yields a mixture of cis-difluoropropene and 2,3-difluoropropene by reductive elimination of the methyl and difluorovinyl groups with an accompanying isomerization in the case of the second product. Finally, protonation of the 2,2,2-trifluoroethylidene-bridged product liberates 1,1,1-trifluoroethane, in which one hydrogen (H(+)) is from the acid while the other hydrogen (H(-)) is derived from activation of the methyl group.

The preparation of a series of new square-planar and half-sandwich type carbenerhodium(I) complexes will be described. The key to success is the use of the bis(stibane)rhodium compound trans-[RhCl(C2H4)(SbiPr3)2] as starting material from which in a stepwise manner the complexes trans-[RhCl(=CRR′)(SbiPr3)2] (L = PiPr3, AsiPr3, SbEt3) and [C5H5Rh(=CCR′)L] (L = SbiPr3, PiPr3, PMe3, CO, CNtBu) have been obtained. Displacement of the carbene ligand in either trans-[RhCl(=CPH2)L2]L = SbiPr3, PiPr3 or [C5H5Rh(=CPh2)(PiPr3)] by CO or CNtBu leads to the formation of the corresponding carbonyl- or isocyanidrhodium compounds and the CC coupling products Ph2C=C=O and Ph2C=C=NtBu, respectively. The carbene ligand is also involved in the selective formation of the isomeric olefins CH2=CHCPh2H and Ph2C=CHCH3 on treatment of trans-[RhCl(=CPh2)(SbiPr3)2] and trans-[RhCl(=CPh2)(PiPr3)2] with ethene. The most spectacular reaction of the bis(triisopropylstibane) complexes, however, occurs on warming of trans-[RhCl(=CRR′)(SbiPr3)2] in the absence of any substrate which yields the first representatives of dinuclear transition-metal compounds containing a tertiary stibane ligand in a bridging position. Some exploratory studies on the reactivity of the Rh2(μ-SbiPr3) complexes indicate that the triisopropylstibane can be replaced by SbMe3, SbEt3 or CNtBu without destroying the dimetallic core of the molecule.

Rietveld crystal structure refinements have been carried out on the X-ray powder patterns of synthetic N-melilite, Y 2 Si 3 N 4 O 3 , and J-phase, Y 4 Si 2 O 7 N 2 . The melilite structure of Y 2 Si 3 N 4 O 3 is confirmed, in which sheets containing Si 2 O 7 double tetrahedra are linked by Y polyhedra in which two of the eight Y-O contacts are significantly longer (2.78A). The present data were unable to furnish unambiguous details of O/N ordering in either N-melilite or J-phase. The structure of J-phase contains either Si 2 O 5 N 2 or Si 2 O 6 N ditetrahedral units containing N in the bridging position and arranged lengthwise along the a -axis. These units are linked by Y polyhedra. Of the four distinguishable Y sites, three have seven contacts with O and N atoms within 2.8A. One of these sites also has one longer O/N contact at 2.92A. The fourth Y site is in 6-fold coordination.

The results of our recent studies devoted to the synthesis of cationic triple-decker complexes are summarized. The stacking reactions of cationic metallofragments with sand-with compounds can be used as a general method for the synthesis of these complexes. This method was used for the preparation of 30- and 34-electron cationic triple-decker complexes containing cyclopentadienyl and pentaphospholyl ligands in the bridging position and carbocycles CnHn (n=4–7) and carboranes as terminal ligands.

One- and two-photon photophysical and photochemical properties of dyes 3-DAC and 4-DAC containing coumarin and benzylidene cyclopentanone moieties were studied. Their ground state configurations were optimized using both Hartree-Fock and density functional theory (B3LYP functional) methods, and excited-state properties were calculated using time-dependent density functional theory. These two dyes share the same formula and possess similar structures, except for different bridging positions between the benzylidene cyclopentanone and coumarin moieties. The bridging position was found to have a significant effect on the electronic structure and photophysical and photochemical properties of the dyes. 3-DAC shows higher conjugation and is more planar than 4-DAC, and it exhibits a larger TPA cross section. In contrast, 4-DAC has a twisted conformation, exhibits a lower electron transfer free energy with initiator and shows higher sensitizing efficiencies in one-photon polymerization. Furthermore, the application potential of 3-DAC and 4-DAC in two-photon polymerization (TPP) was studied. Both dyes could be used directly as initiators in TPP. The TPP threshold energies of the corresponding resins were as low as the best reported results. High-resolution 2D and 3D nanopatterns containing low amounts of small molecule residue were successfully fabricated by TPP, demonstrating the extensive application prospects of these dyes in the fabrication of micromachines, microsensor arrays and biomedical devices.

All attempts to prepare “inidene” compounds [L n E(R) ML n ] + ( A ) with E  Se or Te in the bridging position up until now had been unsuccessful. Although the sulphur analogue [Cp(CO) 2 Mn] 2 SPh + is stable in the “open” form( A ) characteristic of “inidene” compounds, the selenium and tellurium analogues seem to inevitably exist in the valence isomeric ring closed form [L n M-E(R)-M L n ] + ( B ) only. Thermodynamic analyses of the ring opening equilibrium A α B , which had been observed with some sulphur and selenium compounds, led to the hypothesis that sterically demanding substitution at the residue R should make accessible the ring opened forms A . This hypothesis has been confirmed by the synthesis and characterisation of [Cp′(CO) 2 Mn] 2 EMes + (E  Se ( 1 ), Te ( 2 ); Cp′=η 5 -C H 3 C 5 H 4 ). Amongst all compounds of analogous composition [Cp′(CO) 2 Mn] 2 ER + (E  Se, Te) which have been synthesized by now, compounds 1 and 2 are the first and hitherto only compounds of the “inidene”-type A .

Isocyanide- and Heteroallene-Bridged Metal Complexes, IX[1,2]. – Di- and Triiron Complexes with Functional Bridging Isocyanides The reactions of ten mainly functional isocyanide dichlorides RN = CCl2 with Na[FeCp(CO)2] in tetrahydrofuran give mono-isocyanide derivatives [Fe2(Cp)2(CO)3CNR] (1 a–g) of [Fe-Cp(CO)2]2 in which the isocyanide occupies a bridging position. In three cases also minor amounts of diisocyanide complexes [FeCp(μ-CNR)CO]2 (2c, 2e, 8) have been isolated. The chlorocarbonyl-substituted aryl isocyanide dichlorides and pentafluorophenyl isocyanide dichloride in addition suffer (CO)Cl/ and F/ metal exchange, respectively, with formation of μ3-isocyanide-bridged triiron complexes (4 a–c, 7) via the intermediates 5 and 6, 7 has been studied by X-ray analysis.

[Na(MeOCH 2 CH 2 OMe) 2 ][Fe 2 (CN)CP 2 (CO) 3 ] ( 1a ) is prepared from [FeCP(CO) 2 ] 2 and NaCN in hot 1,2-dimethoxyethane; the [N(PPh 3 ) 2 ] +_ ( 1b ), N n BU 4 + - ( 1d ) and PPH 4 + -salts ( 1e ) are obtained by cation exchange, the NEt 4 + -salt ( 1c ) by reaction of Fe 2 CP 2 (CO) 3 NCMe with NEt 4 CN. The X-ray structure analysis of 1b shows a cis -configurated complex anion with long C–O distances in the bridge and a cyano ligand which is disordered between the two terminals positions. In solution, a temperature and solvent dependent equilibrium exists between the more stable cis and the trans complex which is analyzed by IR and 1 H-NMR. It is superimposed by a CN migration between the iron centers via the bridging position which is rapid at -13°C ( trans isomer) and +18°C ( cis isomer), respectively, leading to a coalescence of the Cp signals.

Sulfur(IV) Compounds as Ligands, XIII. – Sulfur Dioxide as a Bridging Ligand in Unsymmetrical Dinuclear Complexes A series of known or newly synthesized dinuclear complexes with the following combinations of elements: Mo/Ir, Mo/Pd, W/Pd, Mn/Pd, Fe/Rh, Rh/Pt, Ir/Pd, and Ir/Pt has been treated with sulfur dioxide. Only electron-rich systems are capable of taking up SO2 into a bridging position. [Mo(CO)3(η2-dppe) (η1-dppm)] (2) reacts with [PdCl2(C8H12)] to form [MoPdCl2(CO)3(dppe)(μ-dppm)] (3), which is unstable and does not take up SO2. However, the complexes [FeRhCl(CO)4(μ-SO2)(μ-dppee)] (5), [MoIr(μ-Cl)(CO)3(μ-SO2)(μ-dppm)2] (8), and [MnPdBr(CO)2(μ-SO2)(μ-dppm)2] (14) have been obtained. Reactions of fac;-[M(CO)3(η2-dppm)(η1-dppm)] (MMo: 6a, W: 6b) or the corresponding mer-isomers 10a, b with [PdCl2;-(C8H12)] give the dinuclear complexes [MPdCl(μ-Cl)(CO)2(μ-CO)(μ-dppm)2] (11a, b). From [Ir(CO)(dppm)2]Cl and [Pd(dba)2] in the presence of CO [IrPdCl(CO)2(μ-dppm)2] (16) is obtained, whereas in dichloromethane under an inert gas the oxidation product [IrPdC]3(CO)(μ-dppm)2] (17) is formed. 11a, b, 16, and 17 apparently are too electron-poor to form stable adducts with SO2. However, from 17 and (Me3Si)2S the sulfur-bridged complex [IrPdCl(μ-S)(CO)(μ-dppm)2] (18) is obtained. The alkynyl complexes [MPtCl(CCPh)2(μ-dppm)2] (M Rh: 19, Ir: 21) readily add SO2, reversibly in the case of 19. From [IrPtCl-(C CPh)2(μ-SO2)](μ-dppm)2] (22) the salt [IrPt(C CPh)2(SO2) (μ-dppm)2]PF6 (23) is formed by Cl abstraction. 23 is one of the rare examples of terminal coordination of SO2 in a dinuclear complex.

The existence and persistence of five-fold (quintuple) bonding in isomers of model RMMR molecules of quite different geometry are examined theoretically. The molecules studied are RMMR, with R = H, F, Cl, Br, CN, and CH3; M = Cr, Mo, and W. The potential energy surface of these molecules is quite complex, containing two, three, even four local minima. The structural preferences in these molecules are rationalized, and electronic factors responsible for these preferences are elucidated. The linear geometry is always a minimum, but almost never the global minimum; there is a definite preference in RMMR for either a trans-bent conformation or perturbations of the trans-bent isomer with at least one of the R groups in a bridging position about the MM bond. The potential energy surface of these RMMR molecules is relatively flat, the lowest energy conformation being that which for a given molecule attains the best compromise between maximization of the MM bonding and minimization of orbital interactions that are MR antibonding. A surprising low-symmetry C(s) structure is identified, which along with the trans-bent isomer is one of the two most popular choices for the global minimum. Regardless of what isomer of the RMMR molecule is preferred, the MM quintuple bond persists.

The X-band powder samples and DMF solution EPR spectra of a series of binuclear copper(II) complexes with binucleating ligand 2,6-diformyl-4-methylphenol di(benzoylhydrazone) (H 3 L) were recorded at both room temperature and 140 K. These complexes incorporate different exogenous ions (X − into a bridging position to form copper(II) binuclear complexes of formula [Cu 2 (H 2 L)X]Y 2 where X − = Br − ( 1 ), Cl − ( 2 ), N 3 − ( 3 ), OC 2 H 5 − ( 4 ), OH − ( 5 ) and pyrazolyl (C 3 H 3 N 2 − ( 6 ) and Y is Br − , Cl − or ClO 4 − . The coupled and uncoupled copper(II) EPR parameters of complexes 3–6 were obtained from DMF solution spectra. The metal-ligand bonding parameters evaluated showed substantial in-plane π-bonding covalency and a small amount of in-plane as well as out-of-plane π-bonding.

The structure of the cationic complex μ-hydrido1:2k 2 H-hydrido-2kH-phenyl-1kC-tetrakis(triethylphosphine)-1k 2 P,2k 2 P-diplatinum(II) consists of two platinum-containing units, which lie on reciprocally perpendicular planes. In each unit, the Pt atom is coordinated in a distorted square-planar arrangement. One hydride ligand is in a bridging position, while the other hydride is terminal on Pt(2). The Pt...Pt distance is 3.093 (1) A