Silicon derivatives of group 1, 2, 11 and 12 elements

Silyl anions and especially silicon derivatives of group 1, 2, 11 and 12 elements are important and versatile organometallic reagents in synthesis. The best-studied class of silyl anions are the alkali metal silanides that feature monomeric, dimeric and polymeric arrangements as molecular units. Alkali metal silanides have not only become interesting for their molecular structures but have also attracted recent attention due to their synthetic abilities. Recently, alkali metal tri- tert -butylsilanides (supersilanides, MSi t Bu 3 ) have been used for the synthesis of new main group element clusters and compounds with elements in low coordination states. In contrast to the well-established silanides with alkali metals, few alkaline-earth metal silanides are known. Information regarding the structure and reactivity of these molecules is thus still rather limited. Silyl derivatives of the zinc group are conveniently accessible by metathesis reaction of MX 2 and alkali metal silanides. X-ray crystal structure analyses show that the silanides of zinc, cadmium and mercury ( t Bu 3 SiMSi t Bu 3 ; M = Zn, Cd, Hg) are monomeric, wheras t Bu 3 SiZnBr and t Bu 3 SiHgCl are tetrameric, the former with a regular, the latter with a pronounced irregular cubic M 4 X 4 framework. The compound (Me 3 SiMe 2 Si) 3 Si Hg Hg Si(SiMe 2 SiMe 3 ) 3 represents the first molecular two-coordinated dinucluear mercury(I) silyl derivative. Contrary to the well-known cuprates with organic ligands, few compounds are known with a Si Cu bond. In contrast to homoleptic transition metal silanides, a huge number of heteroleptic complexes of transition metals with silyl ligands have been synthesized and structurally characterized. Most of them are prepared by addition of silanes, R 3 SiH, to reactive transition metal species.