EXAFS AND X-RAY-DIFFRACTION STUDIES ON THE STRUCTURE OF THE TETRATHIOCYANATOCADMATE(II) COMPLEX IN DIMETHYL-SULFOXIDE

The structure of the tetrathiocyanatocadmate(II) complex in dimethyl sulfoxide (DMSO) has been studied by the EXAFS (extended X-ray absorption fine structure) and solution X-ray diffraction methods. It has been revealed that the tetrathiocyanatocadmate(II) complex has a five-coordinate structure with an additional DMSO molecule. The structure in DMSO is different from that in water and N,N-dimethylformamide, in which no solvent molecule coordinates to the central metal ion. It has also been seen that the coordination mode of the thiocyanate ions in the tetrathiocyanatocadmate(II) complex changes depending on the source of thiocyanate ions due, probably, to different hydrogen bonding abilities of the N- and S-sites of the thiocyanate ion with the counter cations, i.e., the [Cd(NCS)3(SCN)(dMSo)]2- and [Cd(NCS)4(dmso)]2- complexes are formed in solutions containing NH4SCN and (C2H5)4NSCN, respectively. The Cd-N, Cd-S, and Cd-O bond lengths within [Cd(NCS)3(SCN)(dmso)]2- are, respectively, 222(l), 262(1), and 234(l) pm, while the Cd-N and Cd-O bond lengths within [Cd(NCS)4(dmso)]2- are 223(1) and 239(2) pm, respectively.