THE PTCL4(2-) THIAMIN SYSTEM .2. STRUCTURE OF TRANS[PT(DMSO-S)(THIAMIN)CL2](PH4B) AND ITS EQUILIBRIA IN DMSO

Reaction of thiamin nitrate with [Pt(dmso-S)Cl3]- in aqueous solution leads to the formation of the cationic complex trans-[Pt(dmso-S)(thiam in)Cl2]+. Its tetraphenylborate salt was isolated, and its crystal str ucture is reported here: Space group P2(1)2(1)2(1), a = 17.872(6) angs trom, b = 18.822(5) angstrom, c = 11.469(2) angstrom, V = 3858(2) angs trom3, Z = 4, and final discrepancy factor R = 0.0363 for 2423 reflect ions with F > 3sigma(F). The reactions of this complex, Pt(thiamin)Cl3 , and a mixture of cis-Pt(dmso)2Cl2 and (thiamin)Cl were studied with high-field H-1 NMR spectroscopy and Pt-195 NMR spectroscopy in dmso. T he reaction of Pt(thiamin)Cl3 in dmso results in the formation of [Pt( dmso-S)Cl3]- and cis-[Pt(dmso-S)(thiamin)Cl2]+, which subsequently par tially isomerizes to trans-[Pt(dmso-S)(thiamin)Cl2]+. A 1:1 mixture of cis-Pt(dmso-S)2Cl2 and (thiamin)Cl yields trans-[Pt(dmso-S)(thiamin)C l2]+ in the initial stage of the reaction, which then partly isomerize s to cis-[Pt(dmso-S)(thiamin)Cl2]+.