NHC-Stabilized Mixed Group 13/14/15 Element Hydrides.

The syntheses of novel N-heterocyclic carbene (NHC) adducts of group 13, 14 and 15 element hydrides are reported. Salt metathesis reactions between NaPH and IDipp ⋅ GeH BH OTf (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) led to mixtures of the two isomers IDipp ⋅ GeH BH PH (2 a) and IDipp ⋅ BH GeH PH (2 b); by altering the reaction conditions an almost exclusive formation of 2 b was achieved. Attempts to purify mixtures of 2 a and 2 b by re-crystallization from THF afforded a salt [IDipp ⋅ GeH BH  ⋅ IDipp][PHGeH BH PH BH GeH ] (4) that contains the novel anionic cyclohexyl-like inorganic heterocycle [PHGeH BH PH BH GeH ] . In addition, the borane adducts IDipp ⋅ GeH BH PH BH (3 a) and IDipp ⋅ BH GeH PH BH (3 b) as even longer chain compounds were obtained from reactions of 2 a/2 b with H B ⋅ SMe and were studied by NMR spectroscopy. Accompanying DFT computations give insight into the mechanism and energetics associated with 2 a/2 b isomerization as well as their decomposition pathways.