Etude électrochimique de complexes organométalliques: XXVII. Électrogénération du complexe anionique Nb(η5-C5H4SiMe3)2Cl2−

The one-electron reduction of Nb(η⁵-C₅H₄SiMe₃)₂Cl₂ at −30°C yields the corresponding stable anion wich slowly decomposes at room temperature to give [Nb(η⁵C₅H₄SiMe₃)Cl]₂.     

An easy and direct synthetic route to phosphamido niobocenes through nucleophilic attack of phosphide niobocene complexes on acyl halides

The synthesis of the new cationic functionalized phosphane niobocene complexes [Nb(η⁵-C₅H₄SiMe₃)₂(P(CH₂CO(C₆H₅))Ph₂)(L)]Cl, LCO (3) or CNXylyl (4), and new phosphamido-niobocene complexes [Nb(η⁵-C₅H₄SiMe₃)₂(P{CO(C₆H₅)}Ph₂)(L)]Cl, LCO (5), CNXylyl (6), [Nb(η⁵-C₅H₄SiMe₃)₂(P(COCH(C₆H₅)₂)Ph₂)(L)]Cl, LCO (7) or CNXylyl (8), has been achieved. The complexes were prepared by reaction of the Lewis base niobocene complexes [Nb(η⁵-C₅H₄SiMe₃)₂(PPh₂)(L)], LCO (1) or CNXylyl (2), with the appropriate RX (PhCOCH₂Cl, chloroacetophenone) and RCOX (PhCOCl, benzoyl chloride, Ph₂CHCOCl, diphenylacetyl chloride) reagents through the formation of new P–C bonds in the corresponding nucleophilic substitution reactions. These processes afforded new metallophosphanes in which one of the substituents on the phosphorus atom contains a ketonic moiety. The presence of the carbonyl group in the coordination sphere of phosphorus increases the coordination possibilities of the phosphane and enriches the applications of these complexes.     

Synthesis of new chloro methyl niobium and tantalum complexes with silyl-cyclopentadienyl ligands: X-ray crystal structure of [Ta{η-C5H3(SiMe3)2}Cl2Me2]

Trichloro methyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₃Me] (X = Cl, 2; Me, 3), dichloro dimethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₂Me₂] (X = Cl, 4; Me, 5) and tetramethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Me₄] (X = Me, 6; Cl, 7) niobium complexes were synthesized by treatment of starting tetrachloro derivatives [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1a; Me, 1b) with dimethyl zinc or chloro methyl magnesium in different proportions and conditions. A mixture of trichloro methyl and dichloro dimethyl tantalum complexes [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl_4−xMe_x] (x = 1, 8; 2, 9) in a 2:1 molar ratio was obtained in the reaction of [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl₄] (1c) with 0.5 equivalents of ZnMe₂ in toluene at low temperature. 8 could be isolated as single compound when 1 equivalent of 1c was added to the mixtures of 8 and 9, while the reaction of 1c with 1.5 equivalents of dimethyl zinc gave 9 as unitary product. However, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 0.5 equivalents of alkylating reagent giving the trichloro methyl compound [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₃Me] (10) in good yield. On the other hand, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 2 equivalents of MgClMe in hexane at room temperature giving a mixture of dichloro dimethyl and chloro trimethyl complexes[Ta{η⁵-C₅H₃(SiMe₃)₂}Cl_4−xMe_x] (x = 2, 11; 3, 12), while the use of 4 equivalents of MgClMe converts 1c into the tetramethyl derivative [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Me₄] (13). Finally, a tetramethyl tantalum complex [Ta{η⁵-C₅H₃(SiMe₃)₂}Me₄] (14) was prepared by reaction of [Ta{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1c; Me, 1d) with 5 (X = Cl) or 4 (X = Me) equivalents of MgClMe in diethyl ether (X = Cl) or hexane (X = Me), respectively, as solvent. All the complexes were studied by IR and NMR spectroscopy and the molecular structure of the complex 11 was determined by X-ray diffraction methods.     

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.     

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.     

Synthesis and reactivity of new mono- and dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [Ta(η-C5H4SiMe3)Cl2{NC6Me4-4-(N(SiMe3)2)}]

The reaction of [1,4-{SiMe₃(H)N}₂C₆Me₄] (1) with 2 equivalents of LiBuⁿ followed by the addition of SiMe₃Cl gave the diamine compound [1,4-{(SiMe₃)₂N}₂C₆Me₄] (2). [Ta(η⁵-C₅H₄SiMe₃)Cl₄] reacts with 2, in a 2:1 stoichiometric ratio, to initially yield a mixture of the dinuclear, [{Ta(η⁵-C₅H₄SiMe₃)Cl₂}₂(μ-1,4-NC₆Me₄N)] (3), and mononuclear, [Ta(η⁵-C₅H₄SiMe₃)Cl₂{NC₆Me₄-4-(N(SiMe₃)₂)}] (4), imido complexes. 3 can be obtained exclusively by submitting the reaction mixture to repeated cycles of evacuation, to remove volatiles, followed by addition of solvent and subsequent heating. The mononuclear imido complex 4 was isolated from the reaction of [Ta(η⁵-C₅H₄SiMe₃)Cl₄] with 2 in a 1:1 stoichiometric ratio. The molecular structure of 4 was determined by X-ray diffraction studies. [TaCl₃(CH₃CN)₂{NC₆Me₄-4-(N(SiMe₃)₂)}] (5) has been prepared by the reaction of one molar equivalent of TaCl₅ with 2 in a CH₃CN/CH₂Cl₂ solvent mixture. The synthesis of the niobium complexes, [{Nb(η⁵-C₅H₄SiMe₃)Cl₂}₂(μ-1,4-NC₆Me₄N)] (6) and [Nb(η⁵-C₅H₄SiMe₃)Cl₂{NC₆Me₄-4-(N(SiMe₃)₂)}] (7), was achieved in a similar manner to their tantalum analogues. The reactivity of 7 towards nucleophilic reagents, namely lithium benzamidinate, lithium (trimethylsilyl)cyclopentadienyl or lithium dimethylamide, has been studied and the following compounds prepared:[Nb(η⁵-C₅H₄SiMe₃)RCl{NC₆Me₄-4-(N(SiMe₃)₂)}] (R = η⁵-C₅H₄SiMe₃ (8), PhC(NSiMe₃)₂ (9), NMe₂ (10)). In an attempt to form the hetero bimetallic complex, [{Nb(η⁵-C₅H₄SiMe₃)Cl₂}(μ-1,4-NC₆Me₄N){Ta(η⁵-C₅H₄SiMe₃)Cl₂}] (11), the reaction of 7 with [Ta(η⁵-C₅H₄SiMe₃)Cl₄] has been studied. Analysis of the reaction products showed that 11 may exist in equilibrium with the homo bimetallic complexes 3 and 6.     

C2-Bridged sandwich and half-sandwich entities with Ti(IV) and Cr(0) centers

The intense purple colored bi- and trimetallic complexes {Ti}(CH₂SiMe₃)[CC(η⁶-C₆H₅)Cr(CO)₃] (3) ({Ti}=(η⁵-C₅H₅)₂Ti) and [Ti][CC(η⁶-C₆H₅)Cr(CO)₃]₂ (5) {[Ti]=(η⁵-C₅H₄SiMe₃)₂Ti}, in which next to a Ti(IV) center a Cr(0) atom is present, are accessible by the reaction of Li[CC(η⁶-C₆H₅)Cr(CO)₃] (2) with {Ti}(CH₂SiMe₃)Cl (1) or [Ti]Cl₂ (4) in a 1:1 or 2:1 molar ratio. The chemical and electrochemical properties of 3, 5, {Ti}(CH₂SiMe₃)(CCFc) [Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄)] and [Ti][(CC)_nMc][(CC)_mM′c] [n, m=1, 2; n=m; n≠m; Mc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); M′c=(η⁵-C₅H₅)Ru(η⁵-C₅H₄); Mc=M′c; Mc≠M′c] will be comparatively discussed.     

Photochemical reactions of allyl and crotyl halides with cyclopentadienyl-chromium, -molybdenum and -tungsten complexes

[MoCl(CO)₃(η⁵-C₅H₅)] on photolysis with allyl or crotyl halides C₅H₄RX gives Mo^IV complexes [MoX₂(CO)(η³-C₃H₄R)(η⁵-C₅H₅)] (R = H, X = Cl, Br, I; R = Me, X = Cl, Br). [WCl(CO)₃(η⁵-C₅H₅)] under similar conditions gives trihalides [WX₃(CO)₂(η⁵-C₅H₅)] (X = Cl, Br) on reaction with C₃H₅Cl and C₃H₅Br while [WCl(CO)₃(η⁵-C₅H₄SiMe₃)] and [CrI(CO)₃(η⁵-C₅H₅)] react with allyl chloride to give [WCl₃(CO)₂(η⁵-C₅H₄SiMe₃)] and [CrCl₂(η⁵-C₅H₅)] respectively.     

Ein Beitrag zur Reaktivität von (η5-C5Me5)(CO)2FeP(SiMe3)2 gegenüber P-Chlormethylenphosphanen

On the Reactivity of (η⁵-C₅Me₅)(CO)₂FeP(SiMe₃)₂ Toward P-Chloromethylene phosphanes The reaction of (η⁵-C₅Me₅)(CO)₂FeP(SiMe₃)₂ ( 2 ) with three equivalents of Cl? P?C(SiMe₃)₂ ( 3a ) afforded the 3-methanediyl-1,3,5,6-tetraphosphabicyclo[3.1.0]hex-2-ene (η⁵-C₅Me₅)(CO)₂Fe? ( 6a ). In contrast, 2 reacts with two equivalents of Cl? P?C(Ph)SiMe₃ ( 3b ) to give the thermolabile (η⁵-C₅Me₅) · (CO)₂Fe? P[P?C(Ph)SiMe₃]₂ ( 4b ) which decomposed during the reaction with further 3b. 4 b was also obtained from (η⁵-C₅Me₅)(CO)₂Fe? P(SiMe₃)? P?C(SiMe₃)₂ ( 1a ) and two equivalents of 3b .     

Electrochemical studies on organometallic compounds: XLI. Electrogeneration and ESR characterization of [Nb(η5C5H4SiMe3)2Cl{P(OMe)3}]+

In tetrahydrofuran with 0.2 M NaBPh₄ as supporting electrolyte, the one-electron oxidation at −0.4 V relative to an aqueous saturated calomel electrode (SCE) of the electrogenerated species [Nb(η⁵-C₅H₄SiMe₃)₂{ClP(OMe)₃}] (3) yields the cationic niobium(IV) complex [Nb(η⁵-C₅H₄SiMe₃)₂-Cl{P(OMe)₃}]⁺ (4), which has been characterized by ESR spectroscopy. 4 can also be obtained by chemical oxidation of 3.     

Metallo-Carbosiloxan-Dendrimere mit Titanocendichlorid-Endgruppen

The synthesis of titanocenedichloride end-grafted carbosiloxane dendrimers of the 1^st and 2^nd generation is reported. To find the optimal reaction conditions, Me₂ClSiH (1) was reacted with (η⁵-C₅H₄SiMe₂CHCH₂)(η⁵-C₅H₅)TiCl₂ (2). The best result could be obtained with the Karstedt catalyst, whereby exclusively the β-isomer ((η⁵-C₅H₄SiMe₂CH₂CH₂SiMe₂Cl)(η⁵-C₅H₅)TiCl₂, 3) is formed. Under similar conditions Me₃SiOCH(Me)(CH₂)₄SiMe₂H (4) reacts with 2 to give (η⁵-C₅H₄SiMe₂CH₂CH₂SiMe₂(CH₂)₄CH-(Me)OSiMe₃)(η⁵-C₅H₅)TiCl₂ (5). When using MeSi(OCH(Me)(CH₂)₄SiMe₂H)₃ (6), Si(OCH(Me)(CH₂)₄SiMe₂H)₄ (8) and MeSi[O(CH₂)₃SiMe(OCH(Me)(CH₂)₄SiMe₂H)₂]₃ (10) instead of 1 and 4, the respective metallo dendrimers MeSi[OCH(Me)(CH₂)₄-SiMe₂CH₂CH₂SiMe₂(η⁵-C₅H₄)(η⁵-C₅H₅)TiCl₂]₃ (7), Si[OCH(Me)(CH₂)₄SiMe₂CH₂CH₂SiMe₂(η⁵-C₅H₄)(η⁵-C₅H₅)TiCl₂]₄ (9) and MeSi{O(CH₂)₃SiMe[OCH(Me)(CH₂)₄SiMe₂CH₂CH₂SiMe₂(η⁵- C₅H₄)(η⁵-C₅H₅)TiCl₂]₂}₃ (11) can be isolated.Compounds 3, 5, 7, 9 and 11 were characterised by elemental analysis as well as IR and NMR spectroscopy (¹H, ¹³C{¹H}, ²⁹Si{¹H}).     

Dicyclopentadienyl-niobium(iii) and -niobium(iv) complexes

The reduction of (η-C₅H₅)₂NbCl₂ (I) under various conditions gives the dimer (η-C₅H₅)₄Nb₂Cl₃ (II) containing niobium(III) and niobium(IV). Reaction of II with AgClO₄ gives [(η-C₅H₅)₄Nb₂Cl₂]⁺ ClO₄^- (III). FeCl₃ and (C₆F₅)₂ TlBr displace I from II to give (η-C₅H₅)₂Nb(μ-Cl)(μ-X)MY₂, where MFe, XYCl(IV) and MTl, XBr, YC₆F₅ (V). Reactions of I with metal halides MXY₂ give (η-C₅H₅)₂ClNb(μ-Cl)MXY₂ where XYCl, MAl (VI), Fe (VII), Tl (VIII) and XBr, YC₆F₅, MTl (IX). The chemical behaviour of all these compounds is described.     

Komplexe mit sterisch anspruchsvollen Liganden: IV. Gehinderte Rotation der Ringliganden in Tetrakis(trimethylsilyl)metallocenen des Eisens und des Titans

Variable-temperature ¹H NMR studies have revealed that in 1,1′,3,3′-tetrakis(trimethylsilyl)ferrocene, Fe[η⁵-C₅H₃(SiMe₃)₂-1,3]₂, as well as in 1,1′,3,3′-tetrakis(trimethylsilyl)titanocene dichloride, Ti[η⁵-C₅H₃(SiMe₃)₂-1,3]₂Cl₂, the rotation of the five-membered ring about the metal-ring vector is hindered at lower temperatures. The titanocene complex was prepared from TiCl₃ and bis(trimethylsilyl)cyclopentadienyllithium via Ti[η⁵-C₅H₃(SiMe₃)₂-1,3]₂Cl.     

Stabile Bis(alkinyl)-Titanocen-Komplexverbindungen von FeCl2 und CuCl

The application of (η⁵-C₅H₄SiMe₃)₂Ti(CC-SiMe₃)₂ as an organometallic bidentate chelate ligand for MCl₂ building blocks (M = Fe, Co, Ni) is discussed. Reaction of the organometallic substituted alkyne Me₃Si-CC-(η⁵-C₅H₄SiMe₃)₂Ti-CC-SiMe₃, I, with FeCl₂ affords in high yields the dinuclear complex {(η⁵-C₅H₄SiMe₃)₂Ti(CC-SiMe₃)₂}FeCl₂, II. The identy of compound II is confirmed by analytical and spectroscopic data as well as by an X-ray diffraction study. Structural data for L₂Ti(CC-SiMe₃)₂, I, {L₂Ti(CC-SiMe₃)₂}FeCl₂, II, and {L₂Ti(CC-SiMe₃)₂}CuCl, III, (L = η⁵-C₅H₄SiMe₃) are discussed.     

Nickelocene chemistry : II. New methylidyne trinickel cluster compounds

The new methylidene trinickel cluster complexes, [RCNi₃(η⁵-C₅H₅₃] (R  CMe₃ or SiMe₃) and [Me₃SiCNi₃(η⁵-C₅H₅)2(η⁵-C₅H₄CH₂SiMe₃)] have been isolated in low yield from reactions between nickelocene and the corresponding alkyllithium reagents, RCH₂Li. The compounds [RCNi₃(η⁵-C₅H₅)₃] (R  Ph, CMe₃ or SiMe₃) have also been obtained by treatment of the σ-alkylnickel complexes [(η⁵-C₅H₅)Ni(CH₂R)(PPh₃)] with n-BuLi in the presence of an excess of nickelocene, but under similar conditions [(η⁵-C₅H₅)Ni(CH₂C_1OH₇-2)-(PPh₃)] (where C_1OH₇-2  2-naphthyl) failed to give [2-C_1OH₇CNi₃(η⁵-C₅H₅)₃]. The attempted synthesis of [(η⁵-C₅H₅)Ni(CH₂CCH)(PPh₃)] from [(η⁵-C₅H₅)-NiBr(PPh₃)] and CHCCH₂MgBr gave only [(η⁵-C₅H₅)Ni(CCMe)(PPh₃)] by an unusual rearrangement reaction.     

Pyrolysis of metallocene complexes (ηC5H4R)2MR: An organometallic route to metal carbide (MC) materials (M = Ti,Zr, Hf)

The following compounds were prepared and their pyrolysis in a stream of argon was studied: (η⁵-C₅H₅)₂Ti(C?CC₆H₅)₂, (η⁵-C₅H₄SiMe₃)₂-Ti(SH)₂, [(η⁵-C₅H₅)Ti(μ-CH₂)]₂, (η⁵-C₅H₅)₂ZrR₂-(R?CH₂, CH₂C₆H₅, N(CH₃)₂), (η⁵-C₅H₄CH₃)₂-Zr(C?CC₆H₅)₂, [(η⁵-C₅H₄SiMe₃)₂Zr(μ-S)]₂, [(η⁵-C₅H₄SiMe₃)₂Hf(μ-S)]₂ and (η⁵-C₅H₄SiMe₃)₂Hf-(C?CC₆H₅)₂. The products of bulk pyrolysis of these materials were formed in 20–40% yield, based on the charged sample weight, and consisted mainly of titanium carbide together with small amounts of amorphous carbon.     

Synthesis and structures of binuclear half-sandwich cobalt (III) ortho-carboranedithiolato complexes with silyl-bridged bis(cyclopentadienyl) ligands

Five binuclear half-sandwich cobalt complexes, [(η⁵-C₅H₄)Co(CO)I₂]₂SiMe₂ (3), [(η⁵-C₅H₄)Co(S₂C₂B₁₀H₁₀)]₂SiMe₂ (4), [(η⁵-C₅H₄)]₂Co₂(μ₂-S₂C₂B₁₀H₁₀)SiMe₂ (5), [(η⁵-C₅H₃)CoI₂](μ-I)[(η⁵-C₅H₃)Co(CO)I](SiMe₂)₂ (8), [(η⁵-C₅H₃)Co(S₂C₂B₁₀H₁₀)]₂(SiMe₂)₂ (9), were successfully synthesized in moderate yield by the reactions of corresponding ligands, (C₅H₅)₂SiMe₂ (1) and (C₅H₄)₂(SiMe₂)₂ (6), respectively. The molecular structures of 3, 5, 6, 8 and 9 was determined by X-ray crystallographic analysis, which distinctly depict various molecular structures containing the Cp rings and the metal centers with halide or 1,2-dicarba-closo-dodecaborane-1,2-dithiolato ligands. For the (η⁵-C₅H₄)₂SiMe₂ complexes, coordination of the fragments CpCo favors a exo conformation. With the rigid structure of the di-bridged ligand (C₅H₄)₂(SiMe₂)₂, only cis isomers of the corresponding (η⁵-C₅H₃)₂(Si₂Me₂)₂ complexes are formed. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.     

Metallcarbonyl-Synthesen,XIV. Neuartige Vanadium-, Niob- und Tantal-Komplexe mit Wasserstoff-Brücken

Syntheses of Metal Carbonyls, XIV. Novel Vanadium, Niobium, and Tantalum Complexes Having Hydrido Bridges The novel homo- and heterodinuclear organometallic μ-hydrido compounds 3a – c of vanadium, niobium, and tantalum have been synthesized by light-induced reactions of the hydridoniobium complex (η⁵-C₅H₅)₂NbH₃ ( 1 ) with the half-sandwich complexes (η⁵-C₅H₅)M(CO)₄ ( 2a : M = V; 2b : M = Nb; 2c : M = Ta). These compounds have the general composition L_xM – H – Nb(CO)(η⁵-C₅H₅)₂. The formation of the M – H – Nb moieties is a dark-reaction preceded by two photoreactions that are independent from each other elimination of CO from 2a – c and elimination of H₂ from 1 , with the extruded carbon monoxide being transfered to the (η⁵-C₅H₅)₂NbH fragment; subsequent fixation of the species (η⁵-C₅H₅)₂Nb(CO)H thus generated to the photogragments (η⁵-C₅H₅)M(CO)₃ results in donor stabilization of these latter groups. The structural architecture of the derivatives 3a und b was established by X-Ray diffraction. The hydrogen bridges are to be considered as three-center two-electron functions that are responsible for a serious lengthening of the otherwise by at least 40 pm shorter metal-to-metal distances amounting to 371.3 pm in 3a and 373.3 pm in 3b (mean values).     

Übergangsmetall-substituierte Acylphosphane und Phosphaalkene. 22 [1] Insertionen von Hexafluoraceton in die PX-Bindung von Metallophosphanen des Typs (η5-C5Me5)(CO)2M?PX2 (M = Fe,Ru; X = Me3Si,Cl). Strukturbestimmung von (η5-C5Me5)(CO)2Fe?P(SiMe3)C(CF3)2(OSiMe3)

Transition Metal-substituted Acylphosphanes and Phosphaalkenes. 22. Insertions of Hexafluoroacetone into the PX-Bond of Metallophosphanes (η⁵-C₅Me₅)(CO)₂M? PX₂ (M = Fe, Ru; X = Me₃Si, Cl). Structure Determination of (η⁵-C₅Me₅)(CO)₂Fe? P(SiMe₃)C(CF₃)₂(OSiMe₃) Reaction of the metallophosphanes (η⁵-C₅Me₅)(CO)₂M? P(SiMe₃)₂ ( 1a : M = Fe; 1b : M = Ru) with hexafluoroacetone (HFA) afforded the complexes (η⁵-C₅Me₅)(CO)₂M? P(SiMe₃)C(CF₃)₂(OSiMe₃) ( 2a, b ). The attempted synthesis of a metallophosphaalkene from 2a by thermal elimination of hexamethyldisiloxane failed. The acid catalyzed hydrolysis of 2a afforded compound (η⁵-C₅Me₅) · (CO)₂Fe? P(H)C(CF₃)₂(OSiMe₃) ( 3 ). Hexafluoracetone and (η⁵-C₅Me₅)(CO)₂Fe? PCl₂ ( 4 ) under-went reaction to give the metallochlorophosphan (η⁵-C₅Me₅) · (CO)₂Fe? P(Cl)? O? C(CF₃)₂Cl ( 5 ). Constitutions and configurations of the compounds ( 2–5 ) were established by elemental analyses and spectroscopic data (IR, ¹H-, ¹³C, ¹⁹F-, ²⁹Si-, ³¹P-NMR, MS). The molecular structure of 2a was determined by x-ray diffraction analysis.     

Novel Hydrogen Transfer Reactions to the Ligated 1,2,4-Triphosphole in [Ru(η4-C8H12){η-P3C2But 2CH(SiMe3)2}]

INTRODUCTION

As discussed in a recent preliminary publication¹, the complex [Ru(η⁴-C₈H₁₂){η-P₃C₂Bu^t ₂CH(SiMe₃)₂}] (1) (C₈H₁₂ = cycloocta-l,5-diene) was prepared by the reaction of [Ru(η⁶-C₁₀H₈)(η⁴-C₈H₁₂)] (2) (C₁₀H₈ = naphthalene) with the 1,2,4-triphosphole P₃C₂Bu^t ₂CH(SiMe₃)₂ (3) (Fig. 1), illustrating the aromatic behaviour of (3).