The silicon atom in LSiCl or LSiMes (L = PhC(NtBu)(2), Mes = 2,4,6-Me3C6H2) inserts into the B-X bond of RBX2 (R = Ph, Mes, N(SiMe3)(2); X = Cl, Br), which is followed by the migration of the amidinate ligand and the halide atom. By this way, LB(R)SiCl3 (R = Ph, 2; Mes, 3; N(SiMe3)(2), 4) and LB(R)SiX(2)Mes (R = Ph, X = Cl, 5; R = Mes, X = Cl, 6; R = Mes, X = Br, 7) were obtained. Furthermore, a silylene-borane adduct LClSi -> BPhCl2 (1) was obtained as an intermediate in the formation of compound 2. Compounds 2-7 are rare examples of borylhalosilanes.