Coordination polymers from dithiolato complexes and alkali metal cations: How a crystallizing and coordinating solvent influences the dimensionality

Abstract

This article describes the influence of different solvents on the versatility of coordination-networks, formed from alkali metal coordination complex and transition metal bis(dithiolato) complex [M(btdt)2]1− (M = Cu(III) and Au(III); btdt = 2,1,3-benzenethiadiazole-5,6-dithiolate) in compounds 1–7: {[Na(CH3OH)4][Cu(btdt)2]}n (1), {[Na(THF)4][Cu(btdt)2]}n (2), {[Na(CH3COCH3)2][Cu(btdt)2]}n (3), {[Na(DMF)2][Cu(btdt)2]}n (4), {[Na(CH3CN)2][Cu(btdt)2]}n (5) {[Na(THF)2][Na(THF)(OH2)] [Au2(btdt)4]}n (6) and {[Na(CH3COCH3)2][Au(btdt)2]}n (7). The coordination polymers 1–5, based on copper(III)-bis(dithiolene) complex [CuIII(btdt)2]1−, are synthesized by the recrystallization of a dark-brown coloured precipitated precursor (P1) having a black appearance from the different solvents. The precursor P1 was obtained by the reaction of one mole equivalent of CuCl2·2H2O with two mole equivalents of H2btdt in MeOH, treated with an excess amount of NaOH in an open air atmosphere. For the preparation of compounds 6 and 7, AuCl3·2H2O was treated with H2btdt in MeOH containing NaOH to obtain precipitated precursor P2, which was recrystallized from THF and acetone to produce single crystals of 6 and 7 respectively. In the crystal structures of coordination polymers 1–7, where sodium coordination complex is a cationic component, the dimensionality of the networks of the resulting coordination polymers has greatly been influenced by the nature of hybridization of central carbon atom of the sodium-coordinated solvent, which happens to be the recrystallizing solvent. In order to investigate the influence of the counter cation on the structural diversity and dimensionality, we have compared the supramolecular chemistry of these sodium metal based coordination polymers 1–7 with that of our previously reported potassium-based coordination polymers {[K(CH3COCH3)3][Cu(btdt)2]}n and {[K(CH3CN)2][Cu(btdt)2]}n. All these compounds have been characterized unambiguously by single crystal X-ray crystallography and routine spectroscopy (IR, UV-visible and NMR). Interestingly, copper compounds 1 and 3–5 exhibit two quasi-reversible reduction responses at −0.13 V and −1.10 V vs Ag/AgCl respectively in DMF solutions.