Ligand exchange between arylcopper compounds and bis(hypersilyl)tin or bis(hypersilyl)lead: Synthesis and characterization of hypersilylcopper and a stannanediyl complex with a Cu-Sn bond

Bis(hypersilyl)tin (1) and bis(hypersilyl)lead (2) [hypersilyl= Hyp = tris( trimethylsilyl)silyl] undergo ligand exchange reactions with other carbene homologues to yield heteroleptic distannenes or diplumbenes. Here we report the extension of this reaction principle to coordinatively unsaturated ary lcopper(I) compounds. The primary reaction products are probably adducts wi th the carbene homologues as Lewis base and the arylcopper compounds as Lew is acids. This is followed by rearrangement to the adducts HypCu-E-(Hyp)Ar* (E = Sn (6) and Pb (7); Ar* = C(6)H(3)Mes(2)-2,6,) of hypersilylcopper (9) and the heteroleptic stannanediyl or plumbanediyl. The complex may be the final product or may dissociate into its component parts, free hypersilylco pper (9) and the appropriate heteroleptic carbene homologue. The colorless hypersilylcopper forms a trimer (9), in the solid state with short Cu Cu co ntacts (238.4-241.5 pm). All observed Cu-Si bonds are relatively long. Howe ver, shorter distances (234.9-237.4pm) alternate with longer ones (249.2 pm ), such that quasi-monomeric hypersilylcopper units can be identified. The dark green complex 6 exhibits a shorter Cu-Si bond (227.3 pm), The Sn-Cu bo nd length was determined to be 249.9 pm. The turquoise plumbanediyl Pb(Hyp) Ar* (8) is the first strictly monomeric mixed aryl silyl derivative, even i n the solid state. The steric repulsions are obviously less than in the par ent homoleptic compounds because the Pb-C bond in 8 is shorter (229.0 pm) a nd the C-Pb-Si angle (109.2 degrees) is markedly smaller.