On the nature of the SiN double bond and the ease of bending at nitrogen

Abstract

Ab initio calculations (6–31G* basis set) indicate H₂SiNH to be bent (∠SiNH = 126.6°), but to have a low linearization barrier (6.0 kcal/mol at MP4/6–31G*) so that, in accord with experimental results, an electropositive SiH₃ substituent at nitrogen results in a nearly linear structure (∠SiNSi = 175.6°); the SiN double bond is 54.1 kcal/mol weaker than two Si–N single bonds whereas the corresponding difference is only 1.6 kcal/mol for CN vs. two C–N bonds. (1 cal = 4.184 J.)