Aspects of the inorganic chemistry of rubber vulcanisation. Part 1. Reactions of zinc bis(dithiocarbamates) and bis(benzothiazole-2-thiolates) with carboxylates, and the structure of [NBun4][{Zn(S2-CNMe2)2}2(µ-OCOMe)]

Abstract

Reaction of [Zn(S₂CNMe₂)₂] with [NR₄][OCOR′](R = Me or Buⁿ; R′= Me, Et, Prⁿ, or Buⁿ) gives [NR₄][Zn(S₂CNMe₂)₂(OCOR′)], but when R′= n-C₅H₁₁, n-C₆H₁₃, n-C₇H₁₅, n-C₈H₁₇, or C₁₇H₃₅, [NR₄][Zn(S₂CNMe₂)₃] only has been isolated. Treatment of [{Zn(C₇H₄NS₂)₂}_n](C₇H₅NS₂= 2-mercaptobenzothiazole) with [NBuⁿ₄][OCOR′](R′= Me or C₁₇H₃₅) gives only [NBuⁿ₄][Zn(C₇H₄NS₂)₃(OH₂)]. The structure of [NBuⁿ₄][{Zn(S₂CNMe₂)₂}₂(µ-OCOMe)], obtained after recrystallisation of [NBuⁿ₄][Zn(S₂CNMe₂)₂(OCOMe)], has been determined crystallographically. The molecule consists of two five-co-ordinate zinc atoms, each having an essentially square-pyramidal geometry (S₄O co-ordination), bridged by the acetato-group. The relevance of these compounds to certain aspects of the activation of sulphur in rubber vulcanisation is briefly discussed.