Tungsten-silylene complex

Various alkylgermanes add across the Si-C double bond in the silylene complex 116 to yield germyl(silyl)tungsten complexes (Equation (201), Table 25).248... 

Keywords Divalent Silicon Compounds / Molybdenum Compounds / Silylene Complex / Tungsten Compounds / X-Ray Crystal Structures... 

The chemistry of silylene-metal complexes has developed in quite another direction, however, from reactions of disilyl-metal complexes, leading to complexes of otherwise unstable disilenes such as Me2Si=SiMe2. Molybdenum and tungsten complexes have been particularly well investigated by Berry and co-workers,103 and platinum complexes have also been isolated.104 Readers interested in this field are directed to a 1992 review of silylene, silene, and disilene-metal complexes.105... 

The metal, M, can be Fe, Ru, Os (with n = 4) or Cr (n = 5). Substituents on silicon can vary widely, including aryl, alkyl, alkoxy and Et2N groups. With a slight modification, the same reaction is useful for silylene-tungsten complexes (equation 98). 

Insertion of a silylene into a P-P single bond was observed for the reaction of silylene 85 with the diphosphaetidin complex 163. The tungsten complex of l,2,4,3-azadiphosphasilol-5-ene, 164, was obtained in high isolated yields (Equation 14) <2005CC4842>. 

The coordination of stable silylenes to metal complexes was also reported to produce transition metal silylenoids.40,41 Exposure of unsaturated silylene 16 to Ni(CO)4 resulted in the formation of the disilylene-substituted tetrahedral nickel complex 17 (Scheme 7.3).42,43 Similarly, mixing Ph PAuCI with decamethylsilico-cene 18 produced the silylgold complex 19.44 The 29 Si H NMR spectrum of 19 (8 78 ppm) revealed its silylenoid character. In addition to nickel and gold, other metals, including tungsten,41 platinum,45 iron,40 and ruthenium,46 have been utilized to form silylmetal complexes of stable silylenes. 

Intramolecularly alkoxy base-stabilized bis(germylene)-, 54, or (germylene)(silylene)-, 55, iron complexes, of type IV, were obtained from the photolysis of digermyl or germylsilyl iron complexes (equation 43)14. These are the same type of complexes noted above for base-free tungsten analogs146 involving a-elimination subsequent to photochemical elimination of CO as noted below. 

Compound 161 represents a silylene (SiPh2) complex of tungsten, the silylene ligand of which is stabilized by o-donor action of the neighboring acetylene. Formally, the bonding environment of Si is comprised of only four electron pairs, even though the presence of the two acetylene carbon atoms in the coordination shell of Si accounts for the formal coordination number five [330]. 

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