STRUCTURAL AND ELECTRONIC EFFECTS OF ALKYL SUBSTITUENTS ON THE MAIN-GROUP DITHIOCARBAMATO COMPLEXES - CRYSTAL AND MOLECULAR-STRUCTURES OF TRIS(N,N'-IMINODIETHANOLDITHIOCARBAMATO)METAL(III) COMPLEXES (M=AS, SB AND BI) AND CYCLIC VOLTAMMETRIC STUDIES ON SUBSTITUTE DITHIOCARBAMATES

Various dithiocarbamates of As-III, Sb-III and Bi-III with diethyldith iocarbamic acid (dedtc), N-methylaminoethanoldithiocarbamic acid (nmed tc) and N,N'-iminodiethanoldithiocarbamic acid were subjected to cycli c voltammetric reduction studies with a glassy carbon working electrod e. One-electron reduction processes occurs around -1.0 V for As and Sb complexes and around -0.5 V for Bi complexes which are completely irr eversible. Attachment of the polar ends of the molecule is indicated b y the pre- and post-reduction adsorption processes. As the number of - CH2CH2OH groups increases, the peak currents increase. In the case of Bi complexes, the reduction process tends to become reversible. In add ition, the larger peak current associated with the third response indi cates the possible reduction of Bi(dtc)(2)(DMF)(n). In all the complex es the dtc(-) ion was lost from M(dtc)(3)(-) species, with oxidization around +0.6 V in the reverse scans. The crystal structures of As(dead tc)(3) (1), Sb(deadtc)(3) (2) and Bi(deadtc)(3) (3) were determined by single crystal X-ray analysis. The coordination polyhedron in As(dead tc)(3) is a distorted trigonal antiprism, with three strong (2.33-2.35 Angstrom) and three weak (2.82-2.86 Angstrom) As-S bonds. Sb(deadtc)( 3) has a coordination polyhedron which can be described as a distorted pentagonal pyramid. One of the Sb-S bonds is very short (2.46 Angstro m) and differences between others are not significant owing to the lar ger size of antimony compared with arsenic. The stereochemical require ment of the lone pair on Sb has a more pronounced effect in disturbing the neighbouring atoms than that observed in the corresponding As com pounds. The binuclear Bi-2(deadtc)(6) complex is centrosymmetric, two bidentate ligands being bridged in such a way that each sulfur atom is simultaneously bonded to both metal ions. The resulting coordination polyhedron can be described as a distorted square antiprism. The asymm etry in the M-S (M = As, Sb, Bi) bonds is a consequence of the stereoc hemical requirement for the ligand and the lone pair of electrons on t he metals. This is supported by the valence bond sums (VBS) calculated for the complexes. Copyright (C) 1997 Elsevier Science Ltd.