Transition and group IIb metal complexes with "active aldehyde" derivatives of thiamine

The Zn(2+), Cd(2+), Hg(2+), Co(2+) and Ni(2+) ions produce zwitterionic type complexes with the ligands (L), 2-(alpha-hydroxy-benzyl)thiamine=HBT and 2-(alpha-hydroxy-cyclohexyl-methyl)thiamine = HCMT, of the type MLCl(3). The ligands are in the S conformation, the metals are bound to N(1), of the pyrimidine moiety of thiamine and the complexes have a trigonally distorted tetrahedral structure, as the crystal structure of the complex Zn(HCMT)Cl(3) (orthorombic, a=14.4 b=14.1 c=17.4 beta=105.6(O) V=3392A(3) R=13.8%), the one and two dimensional (1)H nmr spectra of the Zn(2+), Cd(2+) and Hg(2+) complexes and the electronic spectra of the Co(2+) and Ni(2+) complexes show. A brief review of the previous techniques (structure of the Hg(HBT)Cl(3) complex, IR-Raman spectra, (13)C nmr in solution and solid state etc) used to characterize these complexes, is also given here and the proper conclusions drawn.