Synthesis and Rearrangement of Stable NHC→Silylene Adducts and Their Unique Reactivity towards Cyclohexylisocyanide

Abstract

The syntheses and reactivity of the two N-heterocyclic carbene (NHC) --> silylene complexes 2 and 4 have been investigated. The latter are easily accessible by reaction of the zwitterionic, N-heterocyclic silylene LSi: 1 [L=Ar-N-C(=CH(2))CH=C(Me)-N-Ar, Ar=2,6-iPr(2)C(6)H(3)] with 1,3,4,5-tetramethylimidazol-2-ylidene and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, respectively. While compound 2 undergoes facile rearrangement above -20 degrees C to give the unsymmetrical N-heterocyclic silylcarbene 3, the derivative 4 remains unchanged even after boiling in benzene. The remarkable reactivity of 3 and 4 towards cyclohexylisocyanide has been examined which leads in a unique series of C-H, Si-H, and C-N bond activations to the new triaminosilanes 5 and 6, respectively. The novel compounds 3, 4, 5, and 6 were fully characterized by (1)H, (13)C, and (29)Si NMR spectroscopy, EI-MS, elemental analysis, and single-crystal X-ray diffraction.