Molecular structures of acetylene derivatives of tin 7.~* Bis(trimethylstannyl)acetylene: analysis of electron diffraction data taking into account nonlineear relations between Cartesian and internal vibrational coordinates

摘要

The electron diffraction data on bis(trimethylstannyl)acetylene, Me_3SnC ident to CSnMe_3, were analyzed in the framework of the one-dimensional dynamic model of free internal rotation of the SnMe_3 group about the axis of the Sn-C ident to C-Sn linear fragment. The root-mean-square amplitudes and harmonic shrinkage coorections used in the analysis were calculated from the scaled quantum-chemical force field (i) taking into account nonlinear relations between Cartesian and internal vibrational coordinates at the first-order level of perturbation theory (h1) and (ii) using a conventional approach (h0). The r_h1 parameters of internuclear distances describe the euilibrium geometry of the Me_3SnC ident to SnMe_3 molecule much better than the commonly accepted parameters r_#alpha# ident to r_h0. Substitutent effects on the geometry of the acetylene fragement are discussed.