Molecular structure and vibrational spectra of bis-N,N'-diethyldithiocarbamate compounds with closed-shell metal ions

The molecular structures of isolated M(Et(2)dtc)(2)(M is Zn-II, Cd-II, Hg-II, Pb-II; Et(2)dtc is (C2H5)(2)NC(S)S-) have been examined by the PM3 and MMP2 methods. The compounds have a compressed tetrahedral (different from the solid state for Zn, Cd, HE) or pyramidal helical (the same as in the solid state for ph) MS4 group. These structures are attributed to the presence of highly strained 4-membered rings MS2C and small bite angles. The pyramidal structure of the Pb(Et(2)dtc)(2) compound suggests that the Pb(II)s(2) lone pair is stereochemically active. Raman spectra recorded in the solid state and in solution (CHCl3 or CH2Cl2) were compared in an attempt to trace the changes that occur in the metal coordination sphere upon dissolution. The band splittings in the solid-state Raman spectra of Zn(Et(2)dtc)(2) and Cd(Et(2)dtc)(2) were attributed to the intermolecular couplings in the dimeric structures: these splittings disappear in the solution spectra. In agreement with its monomeric solid-state structure, the solid state and solution spectra of Pb(Et(2)dtc)(2) were coincident. (C) 1997 Elsevier Science B.V.