Fixation modes of gold(III) from solutions using cadmium(II) dithiocarbamates. Preparation, supramolecular structure and thermal behaviour of polynuclear and heteropolynuclear gold(III) complexes: Bis(N,N-dialkyldithiocarbamato-S,S0)gold(III) polychlorometallates, [Au(S_2CNR_2)_2]_nX (n = 1: X = [AuCl_4]~-; n = 2: X = [CdCl_4]~(2-), [Cd_2Cl_6]~(2-))

摘要

Four novel heteropolynuclear and polynuclear complexes of the general formulae [Au(S_2CNR_2)_2]_2X (X = [CdCl_4]~(2-), R=CH_3 (1); X = [Cd_2Cl_6]~(2-), R=C_3H_7 (2)) and [Au(S_2CNR_2)_2][AuCl_4] (R=iso-C_3H_7 (3); R = iso-C_4H_9 (4)) were prepared using heterogeneous reactions between appropriate freshly precipitated binuclear cadmium(II) dialkyldithiocarbamates and AuCl_3 in 2 M hydrochloric acid. The isolated complexes were studied by ~(13)C CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA) under an argon atmosphere. In all molecular structures (1-4), one of the gold atoms coordinates two dialkyldithiocarbamate ligands in the S,S0-bidentate mode, forming a square-planar coordination polygon [AuS_4], while the other gold atom (in 3 and 4) has four neighbouring chlorine atoms [AuCl_4]. At the supramolecular level, compounds 1 and 2 comprise binuclear cations, [Au_2{S_2CN(CH_3)_2}_4]~(~(~(2+))) and polynuclear chains, ([Au{S_2CN(C_3H_7)_2}_2]~+)_n in a combination with [CdCl_4]~(2-) and [Cd_2Cl_6]~(2-) anions, respectively. Unexpected structural distinctions at the supramolecular level were discovered for the chemically related compounds 3 and 4. In these ionic complexes, there are either cationic trinuclear formations, {[Au{S_2CN(iso-C_3H_7)_2}_2]_2[AuCl_4]}~+, or polynuclear chains, ([Au{S_2CN(iso- C_4H_9)_2}_2]~+)_n, both combined with [AuCl_4]~- anions, in the structural basis of compounds 3 and 4, respectively.