Lewis Acid/Base Reactions of the Bis(amidinato)silylene [iPrNC(Ph)NiPr]₂Si and Bis(guanidinato)silylene [iPrNC(NiPr₂)NiPr]₂Si with ElPh₃ (El = B, Al)

The bis­(amidinato)­silylene [iPrNC­(Ph)­NiPr]₂Si and the analogous bis­(guanidinato)­silylene [iPrNC­(NiPr₂)­NiPr]₂Si react with the Lewis acids BPh₃ and AlPh₃ to form the respective Lewis acid/base adducts 4–7 (adduct 4 has already been described). Compounds 5 and 7 are the first silylene–alane adducts and the first five-coordinate silicon­(II) compounds with an Si–Al bond, and 6 and 7 represent the first silylene–borane and silylene–alane adducts, respectively, that are derived from a bis­(guanidinato)­silylene. Compounds 4–7 were characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy (¹¹B, ¹⁵N, ²⁷Al, ²⁹Si), and 4 and 5 were additionally studied by NMR spectroscopy in solution (¹H, ¹¹B, ¹³C, ²⁷Al, ²⁹Si).