Vibrational analysis of the trigonal bipyramidal NbCl5 and NbBr5 molecules

Abstract

Vibrational normal coordinate analysis has been made for NbCl5 and NbBr5 molecules with D3h symmetry and using Wilson's GF matrix method. The observed frequencies are quantitatively assigned on the basis of the calculated potential energy distribution values for each vibration. The values of force constants for NbCl′ (axial) and NbCl (equatorial) bonds in NbCl5 equal 194 and 261 Nm−1, respectively. The corresponding values for NbBr5 are 142 and 217 Nm−1. These values are discussed in view of the bonding and structure of both compounds.