Hydrosilylation Induced by N→Si Intramolecular Coordination: Spontaneous Transformation of Organosilanes into 1‐Aza‐Silole‐Type Molecules in the Absence of a Catalyst

Our attempts to synthesize the N→Si intramolecularly coordinated organosilanes Ph 2 L 1 SiH ( 1 a ), PhL 1 SiH 2 ( 2 a ), Ph 2 L 2 SiH ( 3 a ), and PhL 2 SiH 2 ( 4 a ) containing a C H N imine group (in which L 1 is the C,N‐chelating ligand {2‐[C H N(C 6 H 3 ‐2,6‐ i Pr 2 )]C 6 H 4 } − and L 2 is {2‐[C H N( t Bu)]C 6 H 4 } − ) yielded 1‐[2,6‐bis(diisopropyl)phenyl]‐2,2‐diphenyl‐1‐aza‐silole ( 1 ), 1‐[2,6‐bis(diisopropyl)phenyl]‐2‐phenyl‐2‐hydrido‐1‐aza‐silole ( 2 ), 1‐ tert ‐butyl‐2,2‐diphenyl‐1‐aza‐silole ( 3 ), and 1‐ tert ‐butyl‐2‐phenyl‐2‐hydrido‐1‐aza‐silole ( 4 ), respectively. Isolated organosilicon amides 1 – 4 are an outcome of the spontaneous hydrosilylation of the C H N imine moiety induced by N→Si intramolecular coordination. Compounds 1–4 were characterized by NMR spectroscopy and X‐ray diffraction analysis. The geometries of organosilanes 1 a – 4 a and their corresponding hydrosilylated products 1 – 4 were optimized and fully characterized at the B3LYP/6‐31++G(d,p) level of theory. The molecular structure determination of 1 – 3 suggested the presence of a SiN double bond. Natural bond orbital (NBO) analysis, however, shows a very strong donor–acceptor interaction between the lone pair of the nitrogen atom and the formal empty p orbital on the silicon and therefore, the calculations show that the SiN bond is highly polarized pointing to a predominantly zwitterionic Si + N − bond in 1 – 4 . Since compounds 1 – 4 are hydrosilylated products of 1 a – 4 a , the free energies (Δ G 298 ), enthalpies (Δ H 298 ), and entropies (Δ H 298 ) were computed for the hydrosilylation reaction of 1 a – 4 a with both B3LYP and B3LYP‐D methods. On the basis of the very negative Δ G 298 values, the hydrosilylation reaction is highly exergonic and compounds 1 a – 4 a are spontaneously transformed into 1 – 4 in the absence of a catalyst.