Heptacoordinated vanadium: Preparation and structure of hexacarbonyl(trimethylstannio)vanadium (Sn—V)

The new complex Me₃SnV(CO)₆ is obtained from TlV(CO)₆ and Me₃SnI in 1,2-C₂H₄Cl₂. Crystals of this complex are composed of molecules Me₃SnV(CO)₆ with heptacoordinated vanadium and a Sn-V bond length of 293.90(6) pm. The molecules possess crystallographic mirror symmetry and approximateC _3v symmetry. The crystal structure determination revealed a remarkable end-for-end orientational disorder in the molecular lattice.Dedicated to Professor Dr. W. Bronger at the occasion of his 60th birthday on July 2nd, 1992.     

Nature of the hydrogen bridge in transition metal complexes: I. Molecular orbital calculations of binuclear carbonyls of Cr,Mo Fe and Ni with single hydrogen bridges

Determination of the electronic structure was performed by the parameter-free Fenske-Hall method for the complexes [(CO)₅MHM(CO)₅]⁻ with D_4h, C_2v and C₂ symmetries (wehre M = Cr, Mo) as well as for the complex [(CO)₃NiHNi(CO)₃]⁻ with C_2v and D_3h symmetries and for the complex [(CO)₄FeHFe(CO)₄]⁺ with a D_3h symmetry.The character and stability of the metalhydrogenmetal bridge bond in each of these complexes was compared. The effect of lowering the symmetry on the electronic structure of these complexes is also discussed. The influence of the bridging hydrogen atom on terminal ligands, i.e. its cis effect, was characterized.     

Linear dichroism of molecules with cubic symmetry

Linear dichroism (LD) of chromophores which belong to the cubic point group of symmetry has been observed. The molecules CrO²⁻₄, Fe(CN)³⁻₆ and Mo(CO)₆ were dissolved in several lyotropic liquid crystals. These systems can be macroscopically aligned which is a prerequisite in LD spectroscopy. The observed LD is ascribed to distortions of the cubic symmetry caused by the uniaxial constraints in the liquid crystals. Contributions to the LD due to the inherent optical birefringence of the systems were taken into account. Furthermore, NMR of CrO²⁻₄ and ESR of Mn²⁺ in various lyotropic liquid crystals strongly support that the symmetry is distorted.     

Crystal and molecular structure at −35°C of (π-cyclobutadiene)dicobalt hexacarbonyl

The structure of cyclobutadienedicobalt hexacarbonyl, (C₄H₄)Co₂(CO)₆, has been determined by single crystal X-ray diffraction techniques with data gathered at ?35°C by counter methods. Crystals form as red prisms in orthorhombic space group Pnma, with lattice parameters (at ?35°C) a = 12.916(3), b = 10.353(2) and c = 9.118(3) Å for a unit cell with four molecules of (C₄H₄)Co₂(CO)₆. The molecules have rigorous C_s symmetry, with a π-cyclobutadiene ring bound to the Co atom of a Co(CO)₂ moiety which, in turn, is linked to a Co(CO)₄ fragment through the metal atoms. Apparently to decrease repulsion between the cyclobutadiene ring and the bulky Co(CO)₄ group, the four-membered ring is tilted, and as a consequence the CoC₄H₄ interaction is unsymmetrical (CoC(ring) = 1.980(3) to 2.048(4) Å). Full-matrix least-squares refinement of the structure has converged with a R index (on |F|) of 0.027 for 1539 symmetry-independent reflections with I_o > 2.0σ(I_o) within the Mo-K_α shell defined by 4° < 2θ < 60°.     

Etude cristallochimique de derives du chrome(0) : I. Structure cristalline et moleculaire du benzoate de methyle chrome dicarbonyle thiocarbonyle

The crystal and molecular structure of methylbenzoatechromium dicarbonyl thiocarbonyl has been determined by a single-crystal X-ray study. The compound crystallizes with two molecules in a unit cell of symmetry P$\text{1}$, with the following parameters: triclinic system, a = 7.108(3), b = 10.340(4), c = 8.523(3) Å; α = 89.75(6), β = 95.89(4), γ = 105.50(4)°; V = 601 ų; d_m = 1.57 ± 0.05, d_c = 1.56. The structure has been refined to R and R″ values of 0.030 and 0.038 respectively, for 1963 independent reflections. The main feature of the molecule is the C_s symmetry of the Cr(CO)₂CS group with a CrC(S) bond length of 1.792(2) Å, shorter than the CrC(O) bond length, mean: 1.849(3) Å.     

Synthesis and x-ray crystallographic characterization of (μ3-Bi)2Fe3(CO)9: A reformulation of Hieber's Bi2Fe5(CO)20

When [HFe(CO)₄]^? is treated first with NaBiO₃ and then dilute H₂SO₄, a complex mixture of neutral metal carbonyl clusters results, some of which can be extracted into petroleum ether. Upon prolonged standing the extract yields a precipitate which has been characterized by X-ray crystallography as Bi₂Fe₃(CO)₉.The complex Bi₂Fe₃(CO)₉ crystallizes in the centrosymmetric orthorhombic space group Cmcm (D_2h¹⁷; No. 63) with a 10.616(2) Å, b 13.458(3) Å, c 11.347(3) Å, V 1621.1(7) ų and Z = 4. Single-crystal X-ray diffraction data (Mo-K_α, 2θ = 4.5–55.0°) were collected on a Syntex P2₁ four-circle diffractometer and the structure was refined to R_F 5.4% and R_WF 4.5% for all 1039 independent data (R_F 4.5% and R_WF 4.5% for those 851 reflections with |F₀| > 3.0σ(|F₀|)). The molecule lies on a site of crystallographic C_2v symmetry and is disordered. The individual molecules have a trigonal bipyramidal Bi₂Fe₃ core with the bismuth atoms occupying the apical sites (BiFe 2.617(2)–2.643(2) Å, FeFe 2.735(5)–2.757(5) Å). Each iron atom is linked to three terminal carbonyl ligands and the molecule has approximate C_3h symmetry. The nine peripheral oxygen atoms are ordered and define a tricapped trigonal prism. The equatorial iron atoms are disordered with the two Fe₃ triangles mutually displaced by approximately 30°; the disordered ensemble has approximate D_3h symmetry.     

Alkyne oligomerization catalyzed by molybdenum(0) complexes

Three new molybdenum(0) complexes, [Mo(CO)₃(Hpz)₃] (1), [Mo(CO)₂(Hpz)₂(DMAD)₂] (2), (DMAD=dimethyl acetylenedicarboxylate) and [Mo(CO)₃(1-Me-imidazole)₃] (3) were synthesized and characterized. Their activity and selectivity in alkyne cyclotrimerization and co-trimerization reactions was investigated. The molecular structures of 1 and 2 have been determined by unconventional powder and standard single-crystal diffraction methods, respectively. 1 consists of a pseudo-octahedral complex of C₃ symmetry, with the ligands in fac disposition; complex 2, of idealized C₂ symmetry, is obtained by substitution of one CO and one pyrazole in 1 by two DMAD ligands, and shows the rare trans configuration of π-bound acetylenic moieties.     

(Chloromethyl)pentacarbonylmanganese(I): a crystal structure with a non-crystallographic centre of symmetry

There are two molecules in the asymmetric unit of the P2₁/c unit cell of ClCH₂Mn(CO)₅, the first halomethyl complex of manganese to be structurally determined. The molecules are crystallographically independent, despite an apparent local centre of symmetry. The average bond parameters include Mn–C_alkyl 2.128(8) Å, C–Cl 1.811(8) Å and Mn–C–Cl 116.4(4)°.     

The structure of an arenemanganese tricarbonyl cation; synthesis and X-ray analysis of dodecahydrotriphenylene(tricarbonyl)manganese(I) tetrafluoroborate

The synthesis, spectroscopic properties, and X-ray structure of dodecahydrotriphenylene(tricarbonyl)manganese(I) tetrafluoroborate, [(η⁶-C₁₈H₂₄)Mn(CO)₃][BF₄] are reported. The cation has approximate C₃ symmetry with the MnCO vectors projected across the unbridged CC bonds of the arene ligand.     

High nuclearity PtRh carbonyl clusters. Synthesis and X-ray characterization of the [Pt2Rh9(CO)22]3− trianion

The new mixed PtRh cluster trianion [Pt₂Rh₉(CO)₂₂]^3? has been isolated as a minor product of the pyrolysis of [PtRh₅(CO)₁₅]^?, and has been characterized by X-ray diffraction. The metal skeleton, which has ideal D_3h symmetry, consists of three face-to-face condensed octahedra, as previously found in the isoelectronic species [Rh₁₁CO)₂₃]^3?, with the Pt atoms on the three-fold axis, in the positions of maximum MM connectivity.     

Synthesis and structural characterization of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH3CO2)Mn(CO)2[P(C6H5)3]2: An organometallic complex containing a chelating acetate ligand

The accidental but intriguing synthesis of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH₃CO₂)Mn(CO)₂[P(C₆H₅)₃]₂, has been accomplished by the reaction of NaMn(CO)₅ with (CH₃)₃SiCl followed by the addition of triphenylphosphine and acetic acid. A three-dimensional single-crystal X-ray diffraction analysis has shown an octahedral-like molecule containing a symmetrically oxygen-chelating acetate group, the first such group to be reported in a metal carbonyl complex. The two triphenylphosphine ligands occupy mutually trans positions with the two carbonyl ligands possessing the remaining cis sites in the octahedral complex. The compound crystallizes with four molecules in a monoclinic unit cell of space group symmetry $\text{P}\text{2}{}_1\text{c}$ and of dimensions a = 17.744(2) Å, b = 9.692(1) Å, c = 20.004(2) Å, and β = 106.195(4)°. The relatively long MnO(acetate) bond lengths [2.066(6) and 2.069(7) Å] and the relatively short MnCO bond lengths [1.701(12) and 1.760(13) Å] and the relatively short MnP(C₆H₅)₃ bond lengths [2.260(3) and 2.275(3) Å], compared to the corresponding MnCO and MnP(C₆H₅)₃ bond lengths in other manganese carbonyl triphenylphosphine complexes, are rationalized on the basis that the acetate ligand in this molecule functions primarily as a σ-donor.     

Structure of hydrogen fluoride complexes with diethylketone in a HF–Et<Subscript>2</Subscript>CO solution

The optimal configurations and the vibrational spectra of heteroassociates (HAs) of hydrogen fluoride and diethylketone molecules with 1:1, 2:2, 4:1, and 8:2 compositions are calculated using the density functional theory (B3LYP/6-31++G(d,p)). A comparison of the results of calculations and the known experimental data reveal that the following stable hydrogen-bonded molecular complexes are formed in HF–Et₂CO solutions: the C _2h symmetry cyclic heterotetramer (HF)₂?(Et₂CO)₂ and the tricyclic HA (HF)₈?(Et₂CO)₂ formed based on the heterotetramer by the binding of two (HF)₃ moieties. It is shown that it is appropriate to decompose the spectral curve into the Gaussian functions or the Lorentzian functions to determine the frequencies and the integrated intensities of broad and overlapped IR bands. The first type of the decomposition enables one to estimate more correctly the values of the band frequencies, and the second type makes it possible to find more correctly the band intensities.     

Reactions of tetracarbonylcobaltate(-I) with chlorosilanes in ether solvents

The reactions of NaCo(CO)₄ with Me_nSiCl_4?n (n = 0–3) in diethylether (Et₂O) and in tetrahydrofuran (THF) have been studied. Three distinct reaction pathways were recognised which depend on the acidity of the chlorosilane and basicity of solvent. Attack at the silicon centre via the Co atom of Co(CO)₄^? leads to formation of a SiCo bond; reaction involving a CO ligand of Co(CO)₄^? gives clusters R₃SiOCCo₃(CO)₉; and chlorosilane induced attack of Co(CO)₄^? on the solvent gives products derived from THF molecules.     

Vibrational spectra and analyses of MFe(CO)4 (M = Cd,Hg)

The IR and Raman spectra of the compounds CdFe(CO)₄ and HgFe(CO)₄, are reported and assigned using C_2v, local symmetry around the iron atom; vibrational analyses of the spectra have also been carried out. The spectroscopic data obtained indicate that the compounds are probably polymers with a centre of symmetry and an octahedral configuration about the iron atom in accordance with X-ray structural results.     

Anisotropic optical polarisabilities of the complexes LCr(CO)5 (L = PMe3, NMe3 or NH3): A study of π-back-bonding

Dipole moments and electric birefringences are reported for the complexes LCr(CO)₅ where L is PMe₃, NMe₃ or NH₃. Comparison of the molecular optical polarisability anisotropies of PMe₃Cr(CO)₅ and NMe₃Cr(CO)₅ shows a large enhancement of polarisability specifically in the L-Cr-(trans)CO direction for the phosphorus compound; the polarisabilities perpendicular to the symmetry axis are closely similar for the two complexes. The results are interpreted as direct evidence for a highly deformable π-component in PCr bonding. This work presents a new experimental approach to the study of π-back-bonding.     

Specific features of the formation of co-adsorption layers on metal surfaces with the participation of simple molecules: NH<Subscript>3</Subscript> + CO on Pt(111)

The co-adsorption of ammonia and carbon monoxide on the Pt(111) surface was studied at temperatures <300 K using high-resolution electron energy loss spectroscopy (HREELS). The state of ammonia and carbon monoxide molecules in the co-adsorption layer was established to differ significantly from their state in individual adsorption layers. The adsorption of CO on a clean surface occurs with the primary filling of single-bound terminal sites, whereas the bridging sites are filled preferably by CO molecules in the presence of NH_3,ads. The symmetry axis of ammonia molecules adsorbed on the clean surface is parallel to the normal to the surface, whereas in the co-adsorption layers the interaction with CO_ads molecules results in the deviation of the symmetry axis toward the surface. Presumably, the observed changes in the state of adsorbed molecules are due to the donor-acceptor interaction inducing the electron density transfer from ammonia molecules across the metal surface to CO molecules.     

Iridium-carbonyl clusters: VI. Mixed-metal clusters via metal-hydride coupling. Synthesis of CpMM′3(CO)11 (M = Mo,W; M′ = Co,Ir) and the crystal structure of CpMoIr3(CO)11

The reaction of CpM(CO)₃H (M = Mo, W), with IrCl(CO)₂(p-toluidine) leads to the species CpMIr₃(CO)₁₁; reaction of CpM(CO)₃H with Co₄(CO)₁₂ produces the known species CpMCo(CO)₁₁ in high yield. The newly-reported species CpMoIr₃(CO)₁₁ has been subjected to an X-ray structural analysis. It crystallizes in the centrosymmetric orthorhombic space group Pbca (No. 61) with a 12.2830(15), b 13.5113(18), c 24.9418(30) Å, V 4139.3(9) ų and Z = 8.Diffraction data were collected with a Syntex P2₁ automated diffractometer (Mo-K_α radiation, 2θ 4.0–45.0°) and the structure was refined to R 5.4% for all 2421 data (R 4.5% for those 2141 data above 3σ(¦F₀¦)).CpMoIr₃(CO)₁₁ is neither isomorphous nor isostructural with the known species CpWIr₃(CO)₁₁ or CpMoCo₃(CO)₁₁. It differs by possessing three bridging carbonyl ligands which encircle one MoIr₂ face of the tetrahedral MoIr₃ cluster. The structure is completed by a Cp ligand on Mo and eight terminal carbonyl ligands (one on the molybdenum atom, three on the unique iridium atom and two each on the iridium atoms associated with the MoIr₂(μ-CO)₃ moiety). The molecule has approximate C_s symmetry.     

Reactions of dodecacarbonyltriosmium with dienic ligands

Dodecacabonyltriosmium reacts with diene ligands (D) such as 2,4-trans, trans- and 2,4-cis, trans-hexadiene and 1,6- and 1,5-heptadiene to give H₂Os₃D(CO)₉, H₄Os₄(CO)₁₂ and two isomers of molecular formula HOs₃-(D  H)(CO)₉ in addition to Os₂(D  2H)(CO)₆ and OsD(CO)₃. The structures of the trimetal complexes show that dehydrogenation, isomerization and rearrangement of the organic substrates occur before the coordination to the metal cluster. 2,3-Dimethyl-1,3-butadiene and dodecacabonyltriosmium give only the well known bi- and mono-metal complexes. The results are compared with those obtained in the reactions of the some organic molecules with dodecacabonyltriruthenium.     

An improved synthesis of the hexaruthenium carbido cluster Ru6C(CO)17; X-ray structure of the salt [Ph4As]2[Ru6C(CO)16]

Reaction of ethylene with Ru₃(CO)₁₂ under conditions of moderate pressure and temperature gives Ru₆C(CO)₁₇ (I) in ca. 70% yield. Reaction of this carbonyl carbido species with base gives the dianion [Ru₆C(CO)₁₆]^2? ; X-ray analysis of the [Ph₄As]⁺ salt indicates an octahedral array of metal atms with the carbon at the centre of the octahedron and twelve terminal and four edge bridging carbonyl ligands giving an approximate overall C_2v symmetry.     

Das verhalten von mono- und diorganylphosphansulfiden gegenüber metallcarbonylsystemen: VII . Präprative,kinetische und spektroskopische untersuchungen über die isomerisierung verschiedener sekundärer phosphansulfide an carbonylsystemen von metallen der VI. nebengruppe

Cycloheptatrienemolybdenum tricarbonyl reacted with ligands (L) (L = phenyl-, o-tolyl-, m-tolyl-, p-tolyl-, α-naphthyl-, β-naphthyl-, sym-diphenyl-, sym-di-o-tolyl-, sym-di-p-tolyl, or sym-di-α-naphthyl-thiourea) to give Mo(CO)₅L derivatives although the expected products were cis-Mo(CO)₃L₃. Evidence has been obtained for the formation of trans-Mo(CO)₄L₂ derivatives when L = sym-diphenyl- and sym-di-o-tolyl-thiourea. These donors on reaction with Mo(CO)₄B (B = o-phenanthroline or 2,2′-bipyridine) yielded mixed ligand derivatives of the type Mo(CO)₃BL. The appearance of three CO stretching bands is in agreement with the C_s symmetry of mixed-ligand molybdenum carbonyls.