Hydrosilylation of a silicon(II) hydride: synthesis and characterization of a remarkable silylsilylene

The synthesis and characterization of novel monomeric silylsilylenes [{PhC(NtBu)(2)}Si--Si{(NtBu)(2)C(H)Ph}R] (R=Cl (2), H (4)) are described. Compound 2 was prepared by the treatment of [{PhC(NtBu)(2)}SiHCl(2)] (1) with two equivalents of potassium graphite, whereas compound 4 was synthesized by the treatment of 1 with four equivalents of potassium graphite. The results suggest that silicon(II) hydride intermediate [{PhC(NtBu)(2)}SiH] was formed in the reduction, which underwent a hydrosilylation with the amidinate ligand of [{PhC(NtBu)(2)}SiR] (R=Cl or H) to form 2 and 4, respectively. The existence of [{PhC(NtBu)(2)}SiH] in solution was demonstrated by the treatment of [{PhC(NtBu)(2)}SiCl] (3) with [K{HB(iBu)(3)}]. Compounds 2 and 4 have been characterized by X-ray crystallography and NMR spectroscopy. The results show that compounds 2 and 4 are stable in solution or the solid state, and do not dimerize to form the corresponding disilene. DFT calculations show that the Si--Si bonds in 2 and 4 do not have multiple-bond character.