Silylisocyanates and silylisothiocyanates: a comparative theoretical study

Structural geometrical parameters, rotational constants, dipole moments and vibrational frequencies of a series of silylisocyanates, R3SiNCO, and silylisothiocyanates, R3SiNCS, with R=H, F, Cl, CH3 have been calculated at different levels of approximation using DFT methods, with B3LYP and B3PW91 functionals, and the MP2 method, using the 6-311G** and 6-311G(2df,2pd) basis sets. The results were compared with available experimental data. The conformation of the Si–N–C–E (E=O, S) skeleton is also discussed analysing statistically the solid state structures, retrieved from the Cambridge Structural Database, containing RnANCE fragments (R=substituent, A=element of the XIV group, E=element of the XVI group).