Rearrangement-Driven Synthesis of Borylhalosilanes from N-Heterocyclic Silylenes and Aminoborondihalides

A selective and efficient synthetic route to borylhalosilanes has been developed via the rearrangement reactions of N-heterocyclic tetrylenes with amino-borondihalides. Functionalized amidinato-substituted silylenes of the type [PhC(NtBu)2SiR] (R = Cl, OtBu, Cbz, Si(SiMe3)3, N(SiMe3)2) react cleanly with amino-borondihalides to afford borylhalosilanes in isolated yields of 30–40%. The process proceeds through migration of the amidinato ligand from Si to B, facilitating ligand exchange between Si(II) and B(III) centers. Notably, the heavier group 14 analogues [PhC(NtBu)2ECl; E = Ge, Sn] follow a divergent pathway involving boron insertion into the amidinate backbone, generating EBr2 precipitates. The resulting products, LBSiBr3Cbz (2a), LBSiBr3tBuCbz (2b), LBSiBr2(OtBu)Cbz (3), LBSiBr2(Cbz)2(4), LBSiBr2[N(SiMe3)2]Cbz (5), LBSiBr2[Si(SiMe3)3]Cbz (6), and LBClCbz (7) (L = PhC(NtBu)2), feature Si(IV) and B(III) centers and were comprehensively characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction studies. These findings establish a versatile platform for generating structurally diverse borylhalosilanes and highlight striking reactivity differences across the group 14 series.