Selenourea as a ligand: visible and infrared spectra of some complexes of selenourea with cobalt, zinc, cadmium, and mercury

Abstract

The donor properties of selenourea (su) are in general very similar to those of thiourea. Ligand field parameters derived from the visible spectra of Co(su)₄(ClO₄)₂ and Co(su)₄(NO₃)₂ are 10 Dq= 4040 cm^–1, β= 0·61. The i.r. spectrum of co-ordinated selenourea is discussed in terms of the calculated potential energy distribution for the planar vibrations of selenourea. Metal–selenium stretching vibrations lie in the frequency range 245–167 cm^–1 decreasing in the order M = Co > Zn > Cd > Hg. The ratio νMSe : νMS in comparable selenourea and thiourea complexes is approximately 0·80. The mercury(II) complex Hg(su)₂Br₂ probably contains planar [Hg(su)₂Br]⁺ ions, but the structures of Hg(su)₂Cl₂ and Hg(su)₂l₂ cannot be determined with any degree of certainty from the i.r. data alone.