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 diethyldithiocarbamic acid (dedtc), N-methylaminoethanoldithiocarbamic acid (nmedtc) and N,N'-iminodiethanoldithiocarbamic acid were subjected to cyclic voltammetric reduction studies with a glassy carbon working electrode. 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 irreversible. Attachment of the polar ends of the molecule is indicated by 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 addition, the larger peak current associated with the third response indicates the possible reduction of Bi(dtc)(2)(DMF)(n). In all the complexes 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(deadtc)(3) (1), Sb(deadtc)(3) (2) and Bi(deadtc)(3) (3) were determined by single crystal X-ray analysis. The coordination polyhedron in As(deadtc)(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 Angstrom) and differences between others are not significant owing to the larger size of antimony compared with arsenic. The stereochemical requirement of the lone pair on Sb has a more pronounced effect in disturbing the neighbouring atoms than that observed in the corresponding As compounds. 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 asymmetry in the M-S (M = As, Sb, Bi) bonds is a consequence of the stereochemical requirement for the ligand and the lone pair of electrons on the metals. This is supported by the valence bond sums (VBS) calculated for the complexes. Copyright (C) 1997 Elsevier Science Ltd.