Synthesis of Base-Free Silyl (silylene) and Germyl (germylene) Complexes

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1. Photolysis of Cp^*W(CO)_3Me (Cp^*=η-C_5Me_5) in the presence of excess HSiMe_2SiMe_3 afforded yellow crystals of a self-stabilized silyl (silylene) tungsten complex with a dimeric structure, [Cp^*W(CO)_2(=SiMe_2)(SiMe_3)]_2(1). In contrast, photolysis of Cp^*W(CO)_3Me in the presence of HSiMe_2SiMeMes_2 (Mes=2,4,6-Me_3C_6H_2) afforded a silyl (silylene) tungsten complex Cp^*W(CO)_2(=SiMes_2)(SiMe_3)(2). Complex 2 is the first "base-free" silyl (silylene) complex. X-ray crystal structure analysis of complex 1 and 2 revealed the significantly short W=Si bond compared to the W-Si bond. The ^<29> Si NMR signal of the silylene ligand for 2 appeared at remarkably low field (δ380.9 ppm) with a tungsten satellite having a large coupling constant (^1J_<SiW>=154.9 Hz). These results clearly demonstrate the double bond character of tungsten-silylene bonding.2. Photolysis of Cp^*W(CO)_3GeMe_2GeMe_3 resulted in the formation of a "base-free" germyl (germylene) tungsten complex Cp^*W(CO)_2(=GeMe_2)(GeMe_3)(3) quantitatively. Complex 3 is the first germylene complex having only small methyl groups on the germanium atoms. Reaction of complex 3 with Fe_2(CO)_9 resulted in the formation of a germylene-bridged dimetal complex Cp^*(OC)_3W(μ-GeMe_2)Fe(CO)_3GeMe_3 quantitatively.