Small Neutral Geminal Silicon/Phosphorus Frustrated Lewis Pairs

Two new silicon/phosphorus‐based frustrated Lewis pairs (FLP), F3SiCH2PtBu2 (1) and Cl3SiCH2PtBu2 (2) were prepared from lithiated di‐tert‐butylmethylphosphane, LiCH2PtBu2, and the corresponding silicon tetrahalides. They were characterised by NMR spectroscopy and by single‐crystal X‐ray diffraction. A gas phase electron diffraction study of 1 identified two conformers of similar energy in the vapor. The reactivity of both, 1 and 2, towards a series of small molecules was investigated. Phenyl isocyanate was found to undergo addition reactions of its C‐N unit to afford five‐membered SiCPC(O)N‐ring structures. Cl3SiCH2PtBu2 (2) was converted with perfluorophenyllithium and 3,5‐bis(trifluoromethyl)phenyllithium. The reaction with LiC6F5 resulted in the ortho‐fluoride substitution product (C6F5)2SiCH2(C6F4)PtBu2 (5), while the aryl reagent without ortho‐fluoride groups, leads to the intramolecular Lewis pair (C8H3F6)3SiCH2PtBu2 (6). The FLP reactivity of 6 was tested. Silicon/phosphorus‐based frustrated Lewis pairs (FLP) with SiF3, SiCl3, and SiR3 groups (R = C6F5 and C6H3(CF3)2) were prepared and their reactivity towards a series of small molecules was investigated: phenyl isocyanate reacts with F3SiCH2PtBu2 and Cl3SiCH2PtBu2 to form five‐membered SiCPC(O)N‐rings.