Cyclopentadienyl molybdenum dicarbonyl η-allyl complexes as catalyst precursors for olefin epoxidation. Crystal structures of Cp′Mo(CO)2(η-C3H5) (Cp′ = η-C5H4Me, η-C5Me5)

The complexes Cp′Mo(CO)₂(η³-C₃H₅) [Cp′ = η⁵-C₅H₅ (1), η⁵-C₅H₄Me (2), η⁵-C₅Me₅ (3)] have been prepared, structurally characterised by X-ray diffraction (2, 3), and tested as catalyst precursors for the epoxidation of olefins at 55 °C. Complex 1 gave a turnover frequency (TOF) of 310 mol mol_Mo⁻¹ h⁻¹ in the epoxidation of cis-cyclooctene with tert-butylhydroperoxide (TBHP, in decane) as oxidant, and 1,2-epoxycyclooctane was obtained quantitatively within 6 h. A similar result was obtained for complex 2, while the TOF for 3 was about one order of magnitude lower, suggesting a possible activity dependence on the ring substituents. For 1 the use of 1,2-dichloroethane as solvent increased the initial reaction rate to 361 mol mol_Mo⁻¹ h⁻¹, with no decrease in epoxide selectivity. Under these conditions the reaction rates for other olefins increased in the order 1-octene < trans-2-octene < cyclododecene < (R)-(+)-limonene < cis-cyclooctene, and, with the exception of limonene, the corresponding epoxide was the only product. For 1 the selective epoxidation of cis-cyclooctene could also be achieved in aqueous solution, using TBHP or H₂O₂ as oxidants, which gave epoxide yields of 99% and 27% at 24 h, respectively. The possibility of facilitating catalyst recycling by using ionic liquids as solvents was investigated.     

Novel chromium trinuclear trifluoroacetate complexes Cr3(μ3-O)(CF3COO)6(CH3COOH)2(CF3COO) and Cr3(μ3-O)(CF3COO)6(CH3COOH)2(THF): Synthesis and crystal structure

Novel anhydrous trinuclear ₃-oxo complexes of Cr(III), Cr₃(₃-O)(CF₃COO)₆(CH₃COOH)₂(CF₃COO) (I) and of Cr(III,III,II), Cr₃(₃-O)(CF₃COO)₆(CH₃COOH)₂(THF) (II) (where THF is (CH₂)₄O) are synthesized by anodic dissolution of metallic chromium in solutions of trifluoroacetic acid in acetonitrile and in tetrahydrofuran and their structures are studied by X-ray diffraction analysis. Complex I forms orthorhombic crystals with space group Pna2₁, a = 9.778(1) , b = 16.042(2) , c = 22.851(4) , Z = 4, R ₁ = 0.0332; complex II crystallizes in monoclinic system: space group P2₁/c, a = 9.866(1) , b = 17.895(2) , c = 21.167(4) , = 100.75(2)°, Z = 4, R = 0.0422. The average Cr-(₃-O) distances in compounds I and II are almost equal (1.943(3) and 1.927(3) ). An average length of the Cr-O bond in octahedral surrounding of metal atoms is different in complexes I and II (1.985(4) and 2.003(3) , respectively), which is specified by different oxidation states of the metal atom. The CrCr distances lie in an interval of 3.366(1)–3.337(1) .__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 266–272.Original Russian Text Copyright © 2005 by Glazunova, Boltalin, Troyanov.     

Synthesis, structure and electrochemistry of CO incorporated diruthenium metallacyclic compounds [Ru2(CO)6{μ-η:η:η:η-1,4-Fc2C5H2O}] and [Ru2(CO)6{μ-η:η:η:η-1,5-Fc2C5H2O}]

Ferrocenyl substituted ruthenium metallacyclic compounds, [Ru₂(CO)₆{μ-η¹:η¹:η²:η²-1,4-Fc₂C₅H₂O}] (1) and [Ru₂(CO)₆{μ-η¹:η¹:η²:η²-1,5-Fc₂C₅H₂O}] (2) have been synthesized and structurally characterized. Electrochemical studies for 1 and 2 and the respective quinone derivatives 3 and 4 show weak to no electrochemical coupling at the mixed-valent intermediate state which is dependent on the complex frameworks.     

Synthesis of Mo(CO)2(η-PPh2(o-C6H4)C(O)H)2 and its reaction with C60

Reaction of Mo(CO)₃(NCMe)₃ and PPh₂(o-C₆H₄)C(O)H (abbreviated as PCHO) at room temperature affords Mo(CO)₂(η³-PCHO)₂ (1), while compound 1 and the phosphine-imine complex Mo(CO)₄(η²-PPh₂(o-C₆H₄)CHNMe) (2) are obtained by using Mo(CO)₃(η³-(MeNCH₂)₃) as the reactant. Thermal reaction of 1 with C₆₀ products Mo(CO)₂(η⁴-(PPh₂(o-C₆H₄)CH)₂)(η²-C₆₀) (3) in low yield, apparently through coupling of the formyl moieties. The structures of 1 and 3 have been determined by an X-ray diffraction study. The two aldehyde groups of 1 and C₆₀ ligand of 3 are coordinated to the molybdenum atom in a π-fashion.     

New ferrocenylmethylphosphines - Preparation, characterisation and coordination chemistry of PH(CH2Fc)2, P(CH2Fc)3 [Fc = Fe(η-C5H5)(η-C5H4)] and their derivatives

The new ferrocenylmethylphosphines PH(CH₂Fc)₂ (1) [Fc = Fe(η⁵-C₅H₅)(η⁵-C₅H₄)] and P(CH₂Fc)₃ (2) and the phosphonium salt [P(CH₂Fc)₃(CH₂OH)]I (3) were synthesised from P(CH₂OH)₃ and [FcCH₂NMe₃]I. [P(CH₂Fc)(CH₂OH)₃]Cl (4) was obtained from P(CH₂Fc)(CH₂OH)₂, CH₂O and HCl. The new phosphines and phosphonium salts were fully characterised by NMR and IR spectroscopy and MS. [Mo(CO)₆] reacts with 1 to give [Mo(CO)₅{PH(CH₂Fc)₂}] (5) in high yield, but attempts to employ 2 as a ligand failed. The reaction of [P(CH₂Fc)₃(CH₂OH)]I (3) and [PH(CH₂Fc)₃]I (obtained in situ from 3 and Na₂S₂O₅) with [WI₂(CO)₃(NCMe)₂] gave the complex salts [P(CH₂Fc)₃(CH₂OH)][WI₃(CO)₄] (6) and [PH(CH₂Fc)₃][WI₃(CO)₄] (7), respectively. [P(CH₂Fc)₄]I (8) was synthesized from PH₂CH₂Fc and [FcCH₂NMe₃]I. Crystal structures were obtained for 1, 3-8.     

Isocyanide insertion reactivity of dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [{Nb(η-C5H4SiMe3)(CH2Ph)2}2(μ-1,4-NC6H4N)]

The reactivity of dinuclear niobium and tantalum imido complexes with the isocyanide compound 2,6-Me₂C₆H₃NC has been studied. The trialkyl complexes [{NbR₃(CH₃CN)}₂(μ-1,3-NC₆H₄N)], [{NbR₃(CH₃CN)}₂(μ-1,4-NC₆H₄N)] and [{TaR₃(CH₃CN)}₂(μ-1,4-NC₆H₄N)] (R=CH₂SiMe₃) gave [{Nb(η²-RCNAr)₂R}₂(μ-1,3-NC₆H₄N)] (1), [{Nb(η²-RCNAr)₂R}₂(μ-1,4-NC₆H₄N)] (2) and [{Ta(η²-RCNAr)₂R}₂(μ-1,4-NC₆H₄N)] (3) (R=CH₂SiMe₃; Ar=2,6-Me₂C₆H₃), from the isocyanide insertion in two of the metal alkyl carbon bonds. The reaction of the isocyanide reagent with the di-alkyl mono-cyclopentadienyl derivatives [{Nb(η⁵-C₅H₄SiMe₃)R₂}₂(μ-1,3-NC₆H₄N)] (R=Me, CH₂Ph, CH₂SiMe₃), [{Nb(η⁵-C₅H₄SiMe₃)R₂}₂(μ-1,4-NC₆H₄N)] (R=Me, CH₂Ph (4), CH₂SiMe₃) and [{Ta(η⁵-C₅Me₅)(CH₂SiMe₃)₂}₂(μ-1,4-NC₆H₄N)] yielded [{Nb(η⁵-C₅H₄SiMe₃)(η²-RCNAr)R}₂(μ-1,3-NC₆H₄N)] (R=Me (5), CH₂Ph (6), CH₂SiMe₃ (7)), [{Nb(η⁵-C₅H₄SiMe₃)(η²-RCNAr)R}₂(μ-1,4-NC₆H₄N)] (R=Me (8), CH₂Ph (9), CH₂SiMe₃ (10)) and [{Ta(η⁵-C₅Me₅)(η²-Me₃SiCH₂CNAr)CH₂SiMe₃}₂(μ-1,4-NC₆H₄N)] (11) (Ar=2,6-Me₂C₆H₃), respectively, from a single insertion process. The reaction with the mono-alkyl complex [{Nb(η⁵-C₅H₄SiMe₃)(Me)Cl}₂(μ-1,4-NC₆H₄N)] gave [{Nb(η⁵-C₅H₄SiMe₃)(η²-MeCNAr)Cl}₂(μ-1,4-NC₆H₄N)] (12), produced from the isocyanide insertion in the metal-alkyl carbon bond. The alkyl-amido complex [{Nb(η⁵-C₅H₄SiMe₃)(Me)NMe₂}₂(μ-1,4-NC₆H₄N)] gave, from the preferential isocyanide insertion in the metal-amide nitrogen bond, [{Nb(η⁵-C₅H₄SiMe₃)(η²-Me₂NCNAr)Me}₂(μ-1,4-NC₆H₄N)] (13). The molecular structure of one of the alkyl precursors, [{Nb(η⁵-C₅H₄SiMe₃)(CH₂Ph)₂}₂(μ-1,4-NC₆H₄N)] (4), has been determined.     

The synthesis and characterisation of some nickel(0) complexes with π-bounded vinylsilicon ligands; the molecular structure of [Ni{P(C6H5)3}2{η-CH2CHSi(CH3)3}]

Reactions of the nickel(0) complexes [Ni(cod)₂] (in the presence of PP or [Ni(PPh₃)₂C₂H₄] with vinyl-siloxanes, -silanes or -silazanes yield, by displacement of alkene ligand, the new nickel π-complexes [Ni(PPh₃)₂(η-CH₂CHSi(OSiMe₃)₃)] (2), [{Ni(PPh₃)}₂{μ-(η-{(CH₂CH)₂SiMe}₂O})] (4), [Ni(PPh₃){η⁴-CH₂CHSi(Me)(μ-O)}₃] (5), [{Ni(η-CH₂CHSiMe₂)₂O}(η-CH₂CHSiMe₃)] (7) and the known complexes [Ni(PPh₃)₂(η-CH₂CHSiMe₃)] (1), [{Ni(PPh₃)}₂{μ-(η-(CH₂CH)₄Si})] (3), [{Ni(PPh₃)(η-CH₂CHSiMe₂)₂NH}] (6) obtained by a simple one pot synthesis, more efficiently than in hitherto published reports. The X-ray crystal structure of (1) shows a trigonal planar environment around the nickel atom.     

Unsaturation in binuclear cyclopentadienylchromium carbonyl thiocarbonyls: Viability of (η-C5H5)2Cr2(CS)2(CO)3 in contrast to (η-C5H5)2Cr2(CO)5

The cyclopentadienylchromium carbonyl thiocarbonyls Cp₂Cr₂(CS)₂(CO)_n (n = 4, 3, 2, 1) have been studied by density functional theory using the B3LYP and BP86 functionals. The lowest energy Cp₂Cr₂(CS)₂(CO)₄ structure can be derived from the experimentally characterized unbridged Cp₂Cr₂(CO)₆ structure by replacing the two terminal carbonyl groups furthest from the Cr-Cr bond with two terminal CS groups. The two lowest energy Cp₂Cr₂(CS)₂(CO)₃ structures have a single four-electron donor η²-μ-CS group and a formal Cr-Cr single bond of length ∼3.1 Å. In contrast to the carbonyl analogue Cp₂Cr₂(CO)₅ these Cp₂Cr₂(CS)₂(CO)₃ structures are viable with respect to disproportionation into Cp₂Cr₂(CS)₂(CO)₄ and Cp₂Cr₂(CS)₂(CO)₂ and thus are promising synthetic targets. The lowest energy Cp₂Cr₂(CS)₂(CO)₂ structures have all two-electron donor CO and CS groups and short CrCr distances around ∼2.3 Å suggesting the formal triple bonds required to give the chromium atoms the favored 18-electron configurations. These Cp₂Cr₂(CS)₂(CO)₂ structures are closely related to the known structure for Cp₂Cr₂(CO)₄. In addition, several doubly bridged structures with four-electron donor η²-μ-CS bridges are found for Cp₂Cr₂(CS)₂(CO)₂ at higher energies. The global minimum Cp₂Cr₂(CS)₂(CO) structure is a triply bridged triplet with a CrCr triple bond (2.299 Å by BP86). A higher energy singlet Cp₂Cr₂(CS)₂(CO) structure has a shorter Cr-Cr distance of 2.197 Å (BP86) suggesting the formal quadruple bond required to give each chromium atom the favored 18-electron configuration.     

X-ray and conformation analysis of the new trinuclear cluster of osmium Os3(μ,η2-OCC6H5)(η3-C3H5)(CO)9

The crystal structure of the Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ cluster synthesized by the reaction of the (μ-H)Os₃(μ-O=CC₆H₅)(CO)₁₀ complex with allylamine in chloroform was determined by X-ray analysis. Prolonged storage of the reaction mixture led to N-C bond cleavage in allylamine and η³-addition of the allyl fragment at one of the Os atoms (Os-C 2.246 ?, 2.248 ?, and 2.273 ?). The unit cell parameters of the complex are a = 9.494(1) ?, b = 10.479(1) ?, c = 12.474(2) ?, α = 84.55(1)°, β = 70.08(1)°, γ = 70.72(1)°, V = 1255.8(4), ?³, space group P , Z = 2; C₁₉H₁₀O₁₀Os₃; d _calc = 2.922 g/cm³, 3085 I _hkl > 2σ _I of 3611 collected reflections; R = 0.0252. The structure of Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ is molecular. The plane of the Os₃ triangle and the OsCOOs plane are connected according to the “butterfly” principle with an angle of 103.4° between them. The Os-Os distances in the cluster core vary from 2.836(1) ? to 2.844(1) ?; the Os-C_carb distances are 1.88(1)–1.97(1) ?; the distances to the atoms of the bridging ligands are Os-C 2.11(1) ?, Os-O 2.14(1) ?; the O-C bridging bond is 1.24(1) ?. of the Os₃(μ,η²-O=CC₆H₅)(η³-C₃H₅)(CO)₉ triosmium cluster were studied theoretically. The potential curve of the internal rotation of the allyl ligand relative to the Os(1)-C(9) bond was determined. The rotation barrier of the allyl ligand in crystal relative to the Os(1)-C(9) bond is 8.38 kJ/mol, and the rotation of the ligand is not hindered. The effects of the intra-and intermolecular interactions on the conformation state of the cluster complex are considered. Original Russian Text Copyright ? 2008 by V. A. Maksakov, N. V. Pervukhina, N. V. Podberezskaya, M. Yu. Afonin, V. A. Potemkin, and V. P. Kirin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 5, pp. 926–932, September–October, 2008.     

Cyclopentadienyl chromium and tungsten complexes with halide, methyl and σ-phenylethynyl ligands: Structures of (η-C5H5)Cr(NO)2(-CC-C6H5), (η-C5H5)Cr(NO)2I and [(η-C5H4)-COOCH3]W(CO)3Cl

With copper(I) iodide as catalyst, σ-alkynyls, compounds (η⁵-C₅H₅)Cr(NO)₂(CC-C₆H₅) (5), [(η⁵-C₅H₄)-COOCH₃]Cr(NO)₂(CC-C₆H₅) (10), and [(η⁵-C₅H₄)-COOCH₃]W(CO)₃(CC-C₆H₅) (13), were prepared from their corresponding metal chloride 1, 6 and 12. Structures of compound 3, 5 and 12 have been solved by X-ray diffraction studies. In the case of 5, there is an internal mirror plane passing through the phenylethynyl ligand and bisecting the Cp ring. The phenyl group is oriented perpendicularly to the Cp with an eclipsed conformation. The twist angle is 0° and 118.4° for -CC-Ph and two NO ligands, respectively. The orientation is rationalized in terms of orbital overlap between ψ₃ of Cp, dπ of Cr atom, and π^∗ of alkynyl ligand, and complemented by molecular orbital calculation. The opposite correlation was observed on the chemical shift assignments of C(2)-C(5) on Cp ring in compounds 6 and 12, using HetCOR NMR spectroscopy. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of ¹³C NMR data and compared with the calculations via density functional B3LYP correlation-exchange method.     

Trimethylsilyl-functionalised bis(indenyl)iron(II) complexes: solid-state structure of [η-1,3-(SiMe3)2C9H5]2Fe

The synthesis of the bis(η⁵-indenyl)iron sandwich complexes (η⁵-1-SiMe₃-C₉H₆)₂Fe (3a), (η⁵-2-SiMe₃-C₉H₆)₂Fe (3b), [η⁵-1,2-(SiMe₃)₂C₉H₅]₂Fe (4a) and [η⁵-1,3-(SiMe₃)₂C₉H₅]₂Fe (4b), by the reaction of the appropriate lithium indenide salts [prepared from 1-SiMe₃-C₉H₇ (2a), 2-SiMe₃-C₉H₇ (2b), 1,2-(SiMe₃)₂C₉H₆ (2c) or 1,3-(SiMe₃)₂C₉H₆ (2d)] with ferrous chloride (1) in a 2:1 molar ratio is discussed. The solid-state structure of 4b was determined by single-crystal X-ray diffractometry. Complex 4b exists in a gauche conformation, showing that the indenyl ligands are sterically imposed by the bulk of the Me₃Si substituents. The average Fe-C distance is 2.091(3) Å. Cyclovoltammetric studies indicate that 3 and 4 are redox-active with one-electron oxidations [E^1/2=−270 to −360 mV versus Fc/Fc⁺, Fc=(η⁵-C₅H₅)₂Fe].     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

Synthesis and structure of the monometallic cationic complex [Cp(CO)2Fe{η-(CH2CHCH2CH3)}]PF6 (Cp = η-C5H5)

The bimetallic carbocation complex [{Cp(CO)₂Fe}₂(μ-C₄H₇)]PF₆ reacted with trifluoroacetic acid to give the mononuclear cationic complex [Cp(CO)₂Fe{η²-(CH₂CHCH₂CH₃)}]PF₆, which formed yellow orthorhombic crystals in the space group P2₁2₁2₁ with a = 7.652(4), b = 13.422(7), c = 14.037(7); α = β = γ = 90.00 and Z = 4. The carbocation is coordinated to the metal in a η²-fashion forming a chiral metallacyclopropane type structure. The β-CH carbon (C9) is disordered over two positions (C9A and C9B), each having about 50% occupancy. This is attributed to there being both the R and S enantioface isomers in equal amounts in the crystal sample. NMR data indicate that the metallacyclopropane structure observed in the solid state is preserved in solution.     

Functionalization of linear and cyclic siloxanes and a dendritic carbosilane with (η-C5H5)Fe(CO)2Si(CH3)2CHCH2 via hydrosilylation reaction

A series of multimetallic systems containing silicon-linked cyclopentadienyl dicarbonyl iron moieties including carbosilane dendrimers and cyclic and polymeric siloxanes have been prepared using hydrosilylation reactions. For this purpose the vinyl-substituted silyliron complex (η⁵-C₅H₅)Fe(CO)₂Si(CH₃)₂ CHCH₂ (1) was prepared by salt elimination reaction between Na[(η⁵-C₅H₅)Fe(CO)₂] and ClSi(CH₃)₂CHCH₂ and fully characterized. Hydrosilylation reaction of 1 with the appropriate Si-H functionalized molecules in the presence of Karstedt catalyst afforded the novel silyl carbonyl iron-functionalized cyclotetrasiloxane 2, dendrimer 3 and copolymer 4, in which the organometallic units are attached to the silicon-based frameworks through a two-methylene flexible spacer. The electrochemical behaviour of compounds 1-4 has been examined in dichloromethane, tetrahydrofuran and acetonitrile solutions using cyclic voltammetry.     

Synthesis and crystal structure of highly soluble ansa-titano- and zirconocene dichloride complexes [Me2Si(η-C5H2(SiMe3)2]2MCl2 (M=Ti, Zr)

The synthesis and X-ray characterization of ansa-metallocene dichloride titanium and zirconium complexes of the type [Me₂Si(η⁵-C₅H₂(SiMe₃)₂)₂]MCl₂ (M=Zr (1), Ti (2)) are reported. The complexes have been tested for ethylene polymerization.     

Crystal structure and spectral characteristics of {[(C6H5)NH]2C=NH(C6H5)}[B(C6H5)4]·C2H5OH

A novel compound of {[(C₆H₅)NH]₂C=NH(C₆H₅)}[B(C₆H₅)₄]·C₂H₅OH is prepared and examined by single crystal X-ray diffraction. Crystal data: C₄₅H₄₄BN₃O, M = 653.64, monoclinic, space group P2₁/c, unit cell parameters: a = 24.375(2) Å, b = 17.5829(15) Å, c = 18.090(1) Å, β = 105.277(2)°, V = 7479.0(11) ų, Z = 8, d _calc = 1.161 g/cm³, T = 293 K, R ₁ = 0.064. The structure contains two crystallographically independent cations, two anions, and two solvate ethanol molecules. Three types of interactions occur between them: interionic N-H(N)⋯π and N(H)⋯π⋯H(C), π-delocalized system of Ph rings of the anions, and interaction of ions with ethanol molecules N-H⋯O-H(O)⋯π. The compound is characterized by IR and luminescence spectra. At room temperature, the emission intensity grows with time of exposure to UV irradiation. Original Russian Text Copyright ? 2008 by T. M. Polyanskaya, E. A. Il’inchik, V. V. Volkov, M. K. Drozdova, O. P. Yur’eva, and G. V. Romanenko __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 3, pp. 512–521, May–June, 2008.     

Facile synthesis and X-ray structures of (η-C5Me5)Ti(OAr)3 (OAr = OC6F5, OCH2C6F5, and OCH2C6F2H3)

New half-sandwich titanocene complexes (η⁵-C₅Me₅)Ti(OC₆F₅)₃ (1), (η⁵-C₅Me₅)Ti(OCH₂C₆F₅)₃ (2), and (η⁵-C₅Me₅)Ti(OCH₂C₆F₂H₃)₃ (3) were synthesized via the displacement of methoxide ligands in (η⁵-C₅Me₅)Ti(OMe)₃ by the corresponding aryloxy or benzyloxy ligands. These compounds have been fully characterized by various spectroscopic methods including X-ray crystallography. Compound 1 has a distorted three-legged piano stool structure. However, complexes 2 and 3 have the chariot-like structure, where chariot means a two-wheeled horse-drawn vehicle. The π electron donation of oxygen atom to Ti center in complexes 1-3 is considerable.     

Synthesis of niobocene imido cations: X-ray crystal structure of [Nb(NBu)(η-C5H4SiMe3)2(CNBu)][BPh4]

The reduction of [Nb(NBu^t)(η⁵-C₅H₄SiMe₃)₂Cl] by sodium amalgam followed by oxidation by [Fe(η⁵-C₅H₅)₂][BPh₄] in the presence of CNBu^t gave [Nb(NBu^t)(η⁵-C₅H₄SiMe₃)₂(CNBu^t)][BPh₄] (1). In a similar manner, [Nb(NPh)(η⁵-C₅H₄SiMe₃)₂(CNBu^t)][BPh₄] (2), [Nb(NPh)(η⁵-C₅H₄SiMe₃)₂(CO)][BPh₄] (3) and [Nb(NBu^t){Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CNBu^t)][BPh₄] (4), were prepared. The reduction of [Nb(NBu^t){Me₂Si(η⁵-C₅H₄)₂}Cl] gave, depending on the experimental conditions, either the d¹-d¹ dimer [(Nb{Me₂Si(η⁵-C₅H₄)₂}(μ-NBu^t))₂] (5) or the hydride derivative [Nb(NBu^t){Me₂Si(η⁵-C₅H₄)₂}H] (6). The reaction of 5 with I₂ led to the formation of [Nb(NBu^t){Me₂Si(η⁵-C₅H₄)₂}I] (7). The molecular structure of 1 was determined by single-crystal X-ray diffraction studies.     

Photochemical reactions of W(CO)6 with hydrosilanes: synthesis, spectroscopic characteristic, and crystal structure of W(CO)3(η-PhSiHPh2)

Photolysis of W(CO)₆ in the presence of Ph₃SiH in n-heptane leads to the formation of the first tricarbonyl(η⁶-triphenylhydrosilane)tungsten complex W(CO)₃(η⁶-PhSiHPh₂) (1) in good yield (ca. 70%). The molecular structure of the new tungsten-silane compound was established by single-crystal X-ray diffraction studies and characterized by IR, UV-Vis, ¹H, ¹³C{¹H}, and ²⁹Si{¹H} NMR spectroscopy.