Sterically hindered chalcogenolato complexes. Mono- and di-meric thiolates and selenolates of zinc and cadmium; structure of [{Cd(SeC6H2But3-2,4,6)2}2], the first three-co-ordinate cadmium–selenium complex

Abstract

Protolysis of M[N(SiMe₃)₂]₂(M = Zn or Cd) with arenechalcogenols 2,4,6-R₃C₆H₂EH (E = S or Se; R = Me, Prⁱ or Bu^t) gives the corresponding chalcogenolato complexes M(EC₆H₂R₃-2,4,6)₂ in high yield. Complexes with R = Me form co-ordination polymers which are soluble only in strongly co-ordinating solvents. An adduct [Cd(SC₆H₂Me₃-2,4,6)₂(py)₂] can be isolated which dissociates in vacuo with quantitative loss of pyridine (py). Complexes with R = Prⁱ readily dissolve in poorly co-ordinating solvents in which they form oligomers. NMR, infrared and Raman evidence suggests that the sterically more hindered tris-tert-butylbenzenechalcogenolato complexes of zinc and cadmium are dimeric in the solid state but dissociate in hydrocarbon solution to give two-co-ordinate monomers. The compound Zn(SeC₆H₂Bu^t₃-2,4,6)₂ forms a 1:1 adduct with tetrahydrofuran. The structure of [{Cd(SeC₆H₂Bu^t₃-2,4,6)₂}₂] was determined by X-ray diffraction. The molecule is an asymmetrically bridged dimer, with three-co-ordinate cadmium in a distorted trigonal-planar arrangement. The Cd–Se distances are ca. 0.1 Å shorter than in comparable four-co-ordinate complexes.