Synthesis and structures of heteroleptic silylenes

The reaction of benzamidinato silicon trichloride [{PhC(NR)(2)}SiCl3] [R = Bu-t (1), SiMe3 (2)] with 2 equiv of potassium in THF afforded mononuclear chlorosilylene [{PhC(NBu')(2)}SiCl] (3) and [{PhC(NSiMe3)(2)}(2)SiCl2] (4), respectively. Compound 4 was formed by the disproportionation of unstable [{PhC(NSiMe3)(2)}SiCl]. The reaction of [{PhC(NBu')(2)}SiCl3] (1) with 1 equiv of UR (R = NMe2, OBut, OPrj, PPr2i) in THF yielded [{PhC(NBut)(2)}SiCl2R] [R = NMe2 (5), OBut (6), OPrj (7), PPr2i (8)]. Treatment of 5-8 with 2 equiv of potassium in THF resulted in the novel heteroleptic silylene [{PhC(NBut)(2)}SiR] [R = NMe2 (9), OBut (10), OPri (11), PPr2i (12)]. Compounds 4, 9, and 12 have been analyzed by X-ray crystallography.