The preparation and structural characterisation of bis(N,N-diethylmonothiocarbamato)complexes of cadmium and of the novel tetrameric complex [Et4Zn4(OSCNEt2)2(NEt2)2]: two new bonding modes for the monothiocarbamato ligand

Abstract

Bis(diethylmonothiocarbamato) complexes of cadmium (1) and zinc (2) were prepared by the reaction of sodium monothiocarbamate with cadmium acetate or zinc chloride. Compound 1 crystallises as clear needles and a single crystal X-ray analysis showed it to be monoclinic (space group C2/c, no. 15), a = 22.143(2), b = 9.239(2), c = 7.553(3) Å, β = 101.41(2)° and Z = 4. The coordination at the cadmium centre is distorted trigonal prismatic with two S,O-bidentate and two O-monodentate diethylmonothiocarbamato ligands. This new, O-binucleating, bonding mode for the monothiocarbamato ligand results in polymeric chains which are co-aligned to give a distorted close-packed hexagonal array.

The cage complex [Et₄Zn₄(OSCNEt₂)₂(NEt₂)₂] 3 is formed as the only isolable product from the reaction of EtZnNEt₂ with carbonyl sulfide. Clear rhombic crystals (space group P2₁/n, no. 14) were formed [a = 10.818(1), b = 14.732(1), c = 11.758(2) Å, β = 103.25(1)° and Z = 2]. The cage is comprised of two six-membered Zn₂CNOS metallocycles that are linked by pairs of Zn–S and Zn–O bonds. In 3 a second new bonding mode for the monothiocarbamato ligand is observed in which both the oxygen and sulfur atoms are binucleating. Molecules of 3 pack to form a slightly distorted cubic close-packed array. The variable temperature ¹H NMR of 3 is also reported and shows the cluster to remain intact in solution.