Synthesis, characterization and reactivity of (dithiolato)indium complexes

We have synthesized indium complexes incorporating tetradentate dithiolate ligands. The 1:1 reaction of InX3 (X = OAc, NO3) and the corresponding dithiol or dithiolate yielded the compounds [(SOOS)In(py) (NO3)] (1), [(SNNS)In(OAc)] (2), [In(mu-SNNS)(2)(mu-OMe)In][NO3] (3), [(SNNSPr)In(OAc)] (4), [(NNS2)In (OAc)] (5) and [(NNS2)In(NO3)] (6) [H-2(SOOS) = 2,2'-(ethylenedioxy)diethanethiol; H-2(SNNS) = N, N'-dimethyl-N,N'-bis(2-mercaptoethyl)ethylenediamine; H-2(SNNSPr) = N,N'-diethyl-N,N'-bis(2-mercaptoethyl)propanediamine; H2(NNS2) N,N-diethyl-N',N'-bis(2-mercaptoethyl)ethanediamine]. The solid-state structures of 1, 2 and 4-6 are mononuclear and show a tetradentate SOOS/SNNS/NNS2 ligand and a distorted octahedral (1) or trigonal bipyramidal (2, 4-6) coordination geometry at indium. Compound 3 is dinuclear, with the indium centres bridged by a -OMe oxygen atom and a thiolate sulfur atom of chelating tetradentate ligands, respectively. InX3 (X = Cl, NO3) were found to be useful Lewis acid catalysts for the aldol reaction of benzaldehyde and 1-(trimethylsiloxy)cyclohexene under ambient conditions, while compounds 1-6 show moderate activity as catalysts for the esterification of stearic acid and transesterification of methyl stearate and glyceryl trioctanoate. (C) 2017 Elsevier Ltd. All rights reserved.