On Silylated Oxonium and Sulfonium Ions and Their Interaction with Weakly Coordinating Borate Anions

Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me₃Si)₃E]⁺ (E=O, S), by reacting [Me₃Si-H-SiMe₃][B(C₆F₅)₄] and Me₃Si[CB] (CB⁻=carborate=[CHB₁₁H₅Cl₆]⁻, [CHB₁₁Cl₁₁]⁻) with Me₃Si-E-SiMe₃. In the reaction of Me₃Si-O-SiMe₃ with [Me₃Si-H-SiMe₃][B(C₆F₅)₄], a ligand exchange was observed in the [Me₃Si-H-SiMe₃]⁺ cation leading to the surprising formation of the persilylated [(Me₃Si)₂(Me₂(H)Si)O]⁺ oxonium ion in a formal [Me₂(H)Si]⁺ instead of the desired [Me₃Si]⁺ transfer reaction. In contrast, the expected homoleptic persilylated [(Me₃Si)₃S]⁺ ion was formed and isolated as [B(C₆F₅)₄]⁻ and [CB]⁻ salt, when Me₃Si-S-SiMe₃ was treated with either [Me₃Si-H-SiMe₃][B(C₆F₅)₄] or Me₃Si[CB]. However, the addition of Me₃Si[CB] to Me₃Si-O-SiMe₃ unexpectedly led to the release of Me₄Si with simultaneous formation of a cyclic dioxonium dication of the type [Me₃Si-μO-SiMe₂]₂[CB]₂ in an anion-mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me₃Si)₃E]⁺ and [(Me₃Si)₂(Me₂(H)Si)E]⁺ ion formation are presented as well as mechanistic investigations on the template-driven transformation of the [(Me₃Si)₃E]⁺ ion into a cyclic dichalconium dication [Me₃Si-μE-SiMe₂]₂²⁺.     

Aluminum(III) Cations [(NHC) ⋅ AlMes2]+: Synthesis,Characterization, and Application in FLP-Chemistry

The three-coordinate aluminum cations ligated by N-heterocyclic carbenes (NHCs) [(NHC) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ (NHC=IMe^Me 4 , IiPr^Me 5 , IiPr 6 , Mes=2,4,6-trimethylphenyl) were prepared via hydride abstraction of the alanes (NHC) ⋅ AlHMes₂ (NHC=IMe^Me 1 , IiPr^Me 2 , IiPr 3 ) using [Ph₃C]⁺[B(C₆F₅)₄]⁻ in toluene as hydride acceptor. If this reaction was performed in diethyl ether, the corresponding four-coordinate aluminum etherate cations [(NHC) ⋅ AlMes₂(OEt₂)]⁺ [B(C₆F₅)₄]⁻ 7 – 9 (NHC=IMe^Me 7 , IiPr^Me 8 , IiPr 9 ) were isolated. According to a theoretical and experimental assessment of the Lewis-acidity of the [(IMe^Me) ⋅ AlMes₂]⁺ cation is the acidity larger than that of B(C₆F₅)₃ and of similar magnitude as reported for Al(C₆F₅)₃. The reaction of [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻ 4 with the sterically less demanding, basic phosphine PMe₃ afforded a mixed NHC/phosphine stabilized cation [(IMe^Me) ⋅ AlMes₂(PMe₃)]⁺[B(C₆F₅)₄]⁻ 10 . Equimolar mixtures of 4 and the sterically more demanding PCy₃ gave a frustrated Lewis-pair (FLP), i.e., [(IMe^Me) ⋅ AlMes₂]⁺[B(C₆F₅)₄]⁻/PCy₃ FLP-11 , which reacts with small molecules such as CO₂, ethene, and 2-butyne.     

Cationic Niobium-Sandwich and Piano-Stool Complexes

The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)₂]⁺ (arene = C₆H₃Me₃, C₆H₅Me) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene)₂]⁺ (arene = C₆H₃Me₃, C₆H₅Me) and [(arene)M(CO)₄]⁺ (arene = C₆H₃Me₃, C₆H₆) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(OR^F)₄]⁻ or [F{Al(OR^F)₃}₂]⁻ (R^F = C(CF₃)₃). The limits of two synthesis routes starting from neutral Nb(arene)₂ (arene = C₆H₃Me₃, C₆H₅Me) or [NEt₄][M(CO)₆] (M = Nb, Ta) were investigated. All compounds were analyzed by single crystal X-ray determination, vibrational and NMR spectroscopy. DFT calculations were executed to support the experimental data.     

Methylalumoxane (MAO)-Derived MeMAO− Anions in Zirconocene-Based Polymerization Catalyst Systems – A UV-Vis Spectroscopic Study

Reaction of Me₂Si(Ind)₂ZrCl₂ with excess methylalumoxane (MAO) gives rise to ion pairs containing zirconocenium cations of the type [Me₂Si(Ind)₂ZrMe]⁺ in contact with two types of anions, MeMAO _A ⁻ and MeMAO _B ⁻, which differ in their coordinative strengths: More strongly coherent contact-ion pairs [Me₂Si(Ind)₂ ZrMe^+..MeMAO _B ⁻] are converted by a sufficiently high excess of MAO to more easily separable contact-ion pairs [Me₂Si(Ind)₂ZrMe^+..MeMAO _A ⁻], which react with AlMe₃ to form the outer-sphere ion pairs [Me₂Si(Ind)₂Zr(µ-Me)₂AlMe₂]⁺ MeMAO _A ⁻, and are likely to be required also for the formation of the olefin-containing reaction complexes responsible for catalytic activity.     

Polymerization of acrylates and bulky methacrylates with the use of zirconocene precursors: Block copolymers with methyl methacrylate

The polymerization behavior of cyclohexyl methacrylate and trimethylsilyloxyethyl methacrylate with the catalytic system Cp₂ZrMe₂/B(C₆F₅)₃/ZnEt₂ was examined. Block copolymers of these bulky methacrylates with methyl methacrylate (MMA), having high molecular weights and relatively narrow molecular weight distributions, were prepared. n‐Butyl acrylate and tert‐butyl acrylate were polymerized with various catalytic systems based on zirconocene complexes. These polymerizations seemed to proceed to a nonquantitative yield, producing polymers with high molecular weights and relatively low polydispersities. This behavior indicated the presence of termination reactions in the initiation step, which appeared to be faster than the propagation step. Block copolymers of these acrylates with MMA were synthesized with the catalytic system rac‐Et(Ind)₂ZrMe₂/[B(C₆F₅)₄]⁻[Me₂NHPh]⁺/ZnEt₂, starting from the polymerization of MMA. The block copolymers produced were well defined in most cases, as indicated by size exclusion chromatography, NMR, and differential scanning calorimetry measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3337–3348, 2005     

Complexation and Versatile Reactivity of a Highly Lewis Acidic Cationic Mg Complex with Alkynes and Phosphines

[(BDI)Mg⁺][B(C₆F₅)₄⁻] ( 1 ; BDI=CH[C(CH₃)NDipp]₂; Dipp=2,6-diisopropylphenyl) was prepared by reaction of (BDI)MgnPr with [Ph₃C⁺][B(C₆F₅)₄⁻]. Addition of 3-hexyne gave [(BDI)Mg⁺ ⋅ (EtC≡CEt)][B(C₆F₅)₄⁻]. Single-crystal X-ray analysis, NMR investigations, Raman spectra, and DFT calculations indicate a significant Mg-alkyne interaction. Addition of the terminal alkynes PhC≡CH or Me₃SiC≡CH led to alkyne deprotonation by the BDI ligand to give [(BDI-H)Mg⁺(C≡CPh)]₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 2 , 70 %) and [(BDI-H)Mg⁺(C≡CSiMe₃)]₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 3 , 63 %). Addition of internal alkynes PhC≡CPh or PhC≡CMe led to [4+2] cycloadditions with the BDI ligand to give {Mg⁺C(Ph)=C(Ph)C[C(Me)=NDipp]₂}₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 4 , 53 %) and {Mg⁺C(Ph)=C(Me)C[C(Me)=NDipp]₂}₂ ⋅ 2 [B(C₆F₅)₄⁻] ( 5 , 73 %), in which the Mg center is N,N,C-chelated. The (BDI)Mg⁺ cation can be viewed as an intramolecular frustrated Lewis pair (FLP) with a Lewis acidic site (Mg) and a Lewis (or Brønsted) basic site (BDI). Reaction of [(BDI)Mg⁺][B(C₆F₅)₄⁻] ( 1 ) with a range of phosphines varying in bulk and donor strength generated [(BDI)Mg⁺ ⋅ PPh₃][B(C₆F₅)₄⁻] ( 6 ), [(BDI)Mg⁺ ⋅ PCy₃][B(C₆F₅)₄⁻] ( 7 ), and [(BDI)Mg⁺ ⋅ PtBu₃][B(C₆F₅)₄⁻] ( 8 ). The bulkier phosphine PMes₃ (Mes=mesityl) did not show any interaction. Combinations of [(BDI)Mg⁺][B(C₆F₅)₄⁻] and phosphines did not result in addition to the triple bond in 3-hexyne, but during the screening process it was discovered that the cationic magnesium complex catalyzes the hydrophosphination of PhC≡CH with HPPh₂, for which an FLP-type mechanism is tentatively proposed.     

Low-Valent MxAl3 Cluster Salts with Tetrahedral [SiAl3]+ and Trigonal-Bipyramidal [M2Al3]2+ Cores (M=Si/Ge)

Schnöckel's [(AlCp*)₄] and Jutzi's [SiCp*][B(C₆F₅)₄] (Cp*=C₅Me₅) are landmarks in modern main-group chemistry with diverse applications in synthesis and catalysis. Despite the isoelectronic relationship between the AlCp* and the [SiCp*]⁺ fragments, their mutual reactivity is hitherto unknown. Here, we report on their reaction giving the complex salts [Cp*Si(AlCp*)₃][WCA] ([WCA]⁻=[Al(OR^F)₄]⁻ and [F{Al(OR^F)₃}₂]⁻; R^F=C(CF₃)₃). The tetrahedral [SiAl₃]⁺ core not only represents a rare example of a low-valent silicon-doped aluminium-cluster, but also—due to its facile accessibility and high stability—provides a convenient preparative entry towards low-valent Si−Al clusters in general. For example, an elusive binuclear [Si₂(AlCp*)₅]²⁺ with extremely short Al−Si bonds and a high negative partial charge at the Si atoms was structurally characterised and its bonding situation analysed by DFT. Crystals of the isostructural [Ge₂(AlCp*)₅]²⁺ dication were also obtained and represent the first mixed Al−Ge cluster.     

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent-Silyliumylidene Cation

The trapping of a silicon(I) radical with N-heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me] (cAAC_Me=:C(CMe₂)₂(CH₂)NAr, Ar=2,6-iPr₂C₆H₃) with H₂SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me)₂Si:^.]⁺I⁻ ( 1 ), which features a cationic cAAC–silicon(I) radical, and [cAAC_Me−H]⁺I⁻. In addition, the reaction of the NHC–iodosilicon(I) dimer [I_Ar(I)Si:]₂ (I_Ar=:C{N(Ar)CH}₂) with 4 equiv of I_Me (:C{N(Me)CMe}₂), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me)₂SiH]⁺I⁻ ( 2 ) comprising the first NHC–parent-silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar−H bond activation product [1-F-2-I_Me-C₆H₄]⁺I⁻ ( 3 ). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1 . Compounds 1 – 3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X-ray crystallography.     

Trapping a Silicon(I) Radical with Carbenes: A Cationic cAAC–Silicon(I) Radical and an NHC–Parent‐Silyliumylidene Cation

The trapping of a silicon(I) radical with N‐heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAAC_Me] (cAAC_Me=:C(CMe₂)₂(CH₂)NAr, Ar=2,6‐i Pr₂C₆H₃) with H₂SiI₂ in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAAC_Me)₂Si:^.]⁺I⁻ ( 1 ), which features a cationic cAAC–silicon(I) radical, and [cAAC_Me−H]⁺I⁻. In addition, the reaction of the NHC–iodosilicon(I) dimer [I_Ar(I)Si:]₂ (I_Ar=:C{N(Ar)CH}₂) with 4 equiv of I_Me (:C{N(Me)CMe}₂), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(I_Me)₂SiH]⁺I⁻ ( 2 ) comprising the first NHC–parent‐silyliumylidene cation. Its further reaction with fluorobenzene afforded the C_Ar−H bond activation product [1‐F‐2‐I_Me‐C₆H₄]⁺I⁻ ( 3 ). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1 . Compounds 1 – 3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X‐ray crystallography.     

Univalent Gallium Complexes of Simple and ansa‐Arene Ligands: Effects on the Polymerization of Isobutylene

Using [Ga(C₆H₅F)₂]⁺[Al(OR^F)₄]^?( 1 ) (R^F=C(CF₃)₃) as starting material, we isolated bis‐ and tris‐η⁶‐coordinated gallium(I) arene complex salts of p‐xylene (1,4‐Me₂C₆H₄), hexamethylbenzene (C₆Me₆), diphenylethane (PhC₂H₄Ph), and m‐terphenyl (1,3‐Ph₂C₆H₄): [Ga(1,4‐Me₂C₆H₄)_2.5]⁺ ( 2⁺ ), [Ga(C₆Me₆)₂]⁺ ( 3⁺ ), [Ga(PhC₂H₄Ph)]⁺ ( 4⁺ ) and [(C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺ ( 5²⁺ ). 4⁺ is the first structurally characterized ansa‐like bent sandwich chelate of univalent gallium and 5²⁺ the first binuclear gallium(I) complex without a Ga?Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI‐BP86/SV(P) level), [Ga(PhC₂H₄Ph)]⁺[Al(OR^F)₄]^?( 4 ) and [(C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺{[Al(OR^F)₄] ^?}₂ ( 5 ), featuring ansa‐arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR‐PIB). In comparison to the recently published 1 and the [Ga(1,3,5‐Me₃C₆H₃)₂]⁺[Al(OR^F)₄]^? salt ( 6 ) (1,3,5‐Me₃C₆H₃=mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR‐PIB with high contents of terminal olefinic double bonds (α‐contents=84–93 %), low molecular weights (M_n=1000–3000 g mol^?1) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6 , the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.     

Exploring the activation of olefin polymerisation catalysts with density functional theory

Density Functional Theory has been used to study the activation of different olefin polymerisation catalysts by different activators. The results show that biscyclopentadienyl catalyst systems would act as the best catalysts and the activators of the type [CPh₃⁺][A⁻] would be the best at activating such systems. The competition between different species present in solution for the vacant active site in the catalyst was studied for the [(1,2Me₂Cp)₂ZrMe⁺][B(C₆F₅)₃CH₃⁻] system and the pre‐catalyst and AlMe₃ were found to be the compounds most likely to form dormant products in solution.     

Cationic titanium alkyls as alkene polymerisation catalysts: Solvent and anion dependence

The ethylene polymerisation activity of [(Ind)₂TiMe]BPh₄ decreases with decreasing solvent polarity but is enhanced if BPh₄⁻ is replaced by the less basic anion [B{C₆H₃(CF₃)₂}₄]⁻. The reaction of [PhNHMe₂]BPh₄ with Cp*₂TiMe₂ gives [Cp*₂TiMe]BPh₄, the first isolable 14-electron titanium alkyl cation complex (Ind = indenyl, Cp* = C₅Me₅).     

The Non-Ancillary Nature of Trimethylsilylamide Substituents in Boranes and Borinium Cations

The known boranes (R(Me₃Si)N)₂BF (R=Me₃Si 1 , tBu 2 , C₆F₅ 3 , o-tol 4 , Mes 5 , Dipp 6 ) and borinium salts (R(Me₃Si)N)₂B][B(C₆F₅)₄] (R=Me₃Si 7 , tBu 8 ) are prepared and fully characterized. Compound 7 is shown to react with phosphines to generate [R₃PSiMe₃]⁺ and [R₃PH]⁺ (R=Me, tBu). Efforts to generate related borinium cations via fluoride abstraction from (R(Me₃Si)N)₂BF (R=C₆F₅ 3 , o-tol 4 , Mes 5 ) gave complex mixtures suggesting multiple reaction pathways. However for R=Dipp 6 , the species [(μ-F)(SiMe₂N(Dipp))₂BMe][B(C₆F₅)₄] was isolated as the major product, indicating methyl abstraction from silicon and F/Me exchange on boron. These observations together with state-of-the-art DFT mechanistic studies reveal that the trimethylsilyl-substituents do not behave as ancillary subsitutents but rather act as sources of proton, SiMe₃ and methyl groups.     

Heavy Carbene Analogues: Donor‐Free Bismuthenium and Stibenium Ions

Kinetically stabilized congeners of carbenes, R₂C, possessing six valence electrons (four bonding electrons and two non‐bonding electrons) have been restricted to Group 14 elements, R₂E (E=Si, Ge, Sn, Pb; R=alkyl or aryl) whereas isoelectronic Group 15 cations, divalent species of type [R₂E]⁺ (E=P, As, Sb, Bi; R=alkyl or aryl), were unknown. Herein, we report the first two examples, namely the bismuthenium ion [(2,6‐Mes₂C₆H₃)₂Bi][BAr^F₄] ( 1 ; Mes=2,4,6‐Me₃C₆H₂, Ar^F=3,5‐(CF₃)₂C₆H₃) and the stibenium ion [(2,6‐Mes₂C₆H₃)₂Sb][B(C₆F₅)₄] ( 2 ), which were obtained by using a combination of bulky meta‐terphenyl substituents and weakly coordinating anions.     

Replacement of Trimethylamine in Trimethylamine‐trispentafluoroethyl‐borane. Structures of [(C2F5)3BNMe3], [NMe4][(C2F5)3BOH], and K[(C2F5)3BCH2(CO)C6H5]

Trimethylamine‐tris(pentafluoroethyl)borane [(C₂F₅)₃BNMe₃] ( 1 ) reacts at 190 °C with water under displacement of the trimethylamine ligand to yield the hydroxy‐tris(pentafluoroethyl)borate [(C₂F₅)₃BOH]^? ( 2 ). In tributylamine 1 reacts with alkynes HC≡CR to form novel ethynyl‐tris(pentafluoroethyl)borate anions [(C₂F₅)₃BC≡CR]^? – R = C₆H₅ ( 3 ), C₆H₄CH₃ ( 4 ), Si(CH(CH₃)₂)₃ ( 5 ) – in moderate yields. Compound 3 adds water across the triple bond to form the novel anion [(C₂F₅)₃BCH₂(CO)C₆H₅]^? ( 6 ). The structures of [(C₂F₅)₃BNMe₃], [NMe₄][(C₂F₅)₃BOH] and K[(C₂F₅)₃BCH₂(CO)C₆H₅] have been determined by x‐ray crystallography.     

Borane‐Catalyzed Cross‐Metathesis Strategy for Facile Transformation of Cyclic (Alkyl)(Amino)Germylenes

A borane B(C₆F₅)₃‐catalyzed metathesis reaction between the Si?C bond in the cyclic (alkyl)(amino)germylene (CAAGe) 1 and the Si?H bond in a silane (R₃SiH; 2 ) is reported. Mechanistic studies propose that the initial step of the reaction involves Si?H bond activation to furnish an ionic species [ 1 ‐SiR₃]⁺[HB(C₆F₅)₃]^?, from which [Me₃Si]⁺[HB(C₆F₅)₃]^? and an azagermole intermediate are generated. The former yields Me₃SiH concomitant with the regeneration of B(C₆F₅)₃ whereas the latter undergoes isomerization to afford CAAGes bearing various silyl groups on the carbon atom next to the germylene center. This strategy allows the straightforward synthesis of eight new CAAGes starting from 1 .     

Zweikernige silylenverbrückte Cyclopentadienylrhodiumbis(ethen)-Komplexe,photochemische Reaktion mit Benzolderivaten und selektiver Einschluß von Methylcyclopentan in das Kristallgitter von [Me2Si{3-But-C5H3Rh(C2H4)2}2]

Dinuclear Silylene Bridged Cyclopentadienylrhodiumbis(ethene) Complexes, Photochemical Reaction with Benzene Derivatives, and Selective Inclusion of Methylcyclopentane into the Crystal Lattice of [Me₂Si{3-Bu^t-C₅H₃Rh(C₂H₄)₂}₂] By reaction of [{(C₂H₄)₂RhCl}₂] with Na₂[Me₂Si(C₅H₄)₂] or with Li₂[Me₂Si(3-Bu^t-C₅H₃)₂] in THF the dinuclear silylene bridged complexes [Me₂Si{C₅H₄Rh(C₂H₄)₂}₂] 1 and [Me₂Si{3-Bu^t-C₅H₃Rh(C₂H₄)₂}₂] 2 , respectively, were synthesized. Due to the asymmetric substitution of the five-membered rings and their hindered rotation around the Si? C axes, 2 is formed as three isomers. The X-ray structure analysis of 2 obtained from hexane reveals the selective inclusion of methylcyclopentane, the content of which in the solvent is about 17%, into the crystal lattice. UV irradiation of 1 in hexane in the presence of benzene causes elimination of the ethene ligands yielding the μ-η³:η³ benzene complex [Me₂Si(C₅H₄Rh₂)₂C₆H₆] which cannot be separated from unreacted 1 . However, separation is possible in case of the hexamethylbenzene compound 4 analogous with 3 .     

Synthesis and reactivity of [2]disilaniobocenophanes

The paramagnetic ansa-niobocene [(Me₂Si)₂(η⁵-C₅H₄)₂NbCl₂] (1) was obtained from the reaction of Li₂[(Me₂Si)₂(C₅H₄)₂] with [NbCl₄(thf)₂]. Further treatment with Li[AlH₄] yielded [(Me₂Si)₂(η⁵-C₅H₄)₂NbH₃] (3), which is prone to decomposition within a few days at room temperature both in solution and in the solid-state, thus affording primarily an insoluble black material. However, after heating or irradiation of a solution of 3 small quantities of the dimeric niobium hydride species, [(Me₂Si)₂{μ-(η¹:η⁵-C₅H₃)}(η⁵-C₅H₄)NbH]₂ (4), were isolated and characterized by X-ray diffraction.     

Ouebergangsmetall-substituierte phosphane,arsane und stibane: LI. Bis-metallate Na2{Me2Si[(C5H4)(CO)3M]2} (M = Mo,W): darstellung und umwandlung in neutralkomplexe Me2Si[(C5H4)(CO)3MR]2 (R = Me,AsMe2) mit σ-gebundener dimethylarsenido- oder methylgruppe

The bis(sodium-metallates) Na₂{Me₂Si[(C₅H₄)M(CO)₃]₂} (4a: M = Mo, 4b, M = W), in which the metal centres are linked by their cyclopentadienyl ligands through a Me₂Si unit are obtained by the reaction of Na₂[(C₅H₄)₂SiMe₂] (2) with two moles M(CO)₆ (3a: M = Mo; 3b: M = W). Treatment of 4a with Me₂AsCl leads to the formation of the bis(metalloarsane) Me₂Si[(C₅H₄(CO)₃^- MoAsMe₂]₂ (5), which is quarternized by MeI at the arsenic atoms to give the dicationic complex {Me₂Si[(C₅H₄)(CO)₃MoAsMe₃]₂}I₂ (7). In reactions with the ylide Me₃PCH₂ cleavage of the MoAs bonds occurs, followed by transylidation to yield the bis(phosphonium metallate) [Me₄P]₂ {Me₂Si[(C₅H₄)Mo- (CO)₃]₂} (10) and Me₃PCHAsMe₂ (9). From 4a, 4b and MeI the dinuclear methyl complexes Me₂Si[(C₅H₄)(CO)₃MMe]₂ (6a: M=Mo; 6b: M=W) are obtained.     

Trimethylsilylsubstituierte Cyclopentadienylindium(I) Verbindungen; Synthese and Eigenschaften

Reaction of indium(I) chloride with trimethylsilylated cyclopentadienyllithium species yields the air- and moisture-sensitive cyclopentadienylindium complexes In[(Me₃Si)C₅H₄] (1), In[(Me₃Si)₂C₅H₃] (2) and In[(Me₃Si)₃C₅H₂] (3), which are volatile and easily soluble in nonpolar solvents. Compound 1 crystallizes as a chain polymer.