Metal ion interactions with thiamine. Crystal structures of Co(thiamine)Cl3·0.4H2O and Zn(thiamine)Br3·0.2H2O: metal bonding to the base

The crystal structures of Co(thiamine)Cl3·0.4H2O (1) and Zn(thiamine)Br3·0.2H2O (2) have been determined by X-ray diffraction. The compounds are isomorphous to each other. Each compound forms a discrete M(thiamine)X3 (M=Co(II) and X=Cl−; M=Zn(II) and X=Br∝-) structure with the tetrahedral M(II) atom being bonded by the three halide atoms and the N(1′) atom of the pyrimidine ring. The thiamine ligand adopts the S conformation: oT and oP=128.9(3) and 111.8(4)° for 1 and 130.5(9) and 113.5(9)° for 2. A ‘two-point’ halide bridge between the pyrimidine and the thiazolium moieties of the same molecule through an N(4′α)H···X(1) hydrogen bond and an X(2)···thiazolium electrostatic contact is a factor that affects the S conformation. Crystal data: 1, monoclinic, space group C2/c, a=25.767(9), b=8.490(2), c=17.539(6) A, β=106.24(1)°, Z=8, Dcalc=1.579 g cm−3 and R=0.045 for 3508 observed reflections; 2, monoclinic, space group C2/c, a=26.388(5), b=8.563(1), c=17.753(3) A, β=105.95(1)°, Z=8, Dcalc=1.977 g cm−3 and R=0.051 for 1991 observed reflections.