Stable silylene–isocyanide complexes [Tbt(Mes)SiCNAr (Ar = Tbt, Mes*; Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl; Mes = mesityl; Mes* = 2,4,6-tri-t-butylphenyl)] reacted with BH3·THF to give the firststable silylborane–isocyanide complexes [Tbt(Mes)SiHBH2CNAr]. The thermal equilibrium between Tbt(Mes)SiHBH2CNAr and TbtSiH2BH(Mes)CNAr was observed.