IMIDAZOLE DERIVATIVES .8. CARBENE COMPLEX ES OF SILICON AND TIN

Stable adducts of the composition L . SiCl4 (2), L . SiR(2)Cl(2) (3, 4 ), and L . SnR(2)Cl(2) (6) are formed by the reaction of the imidazol- 2-ylidenes L (1) with the corresponding silicon and tin halides. For L . SiCl4 (2b; L = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) and L . SnPh(2)Cl(2) (6c; L = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) the monomeric nature of the compounds containing pentacoordinated sili con and tin is established by X-ray structure analyses. The reaction o f 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (Ic) with SnCl2 leads to the formation of the monomeric stannylene complex L . SnCl2 (7c; L = 2,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) whose molecular geo metry indicates a week carbon-to-tin donor bond [Sn-C(1) 2.290(5) Angs trom].