Metal ion and anion coordination in the thiamine–[Pt II(NO 2) 4] 2− system. Structures of a metal complex, Pt(thiamine)(NO 2) 3, and two salts, (H-thiamine)[Pt(NO 2) 4]·2H 2O and (thiamine monophosphate) 2[Pt(NO 2) 4]·2H 2O

Abstract

Reaction of thiamine or thiamine monophosphate (TMP) with K 2Pt(NO 2) 4 afforded a metal complex, Pt(thiamine)(NO 2) 3 ( 1), and two salt-type compounds, (H-thiamine)[Pt(NO 2) 4]·2H 2O ( 2) and (TMP) 2[Pt(NO 2) 4]·2H 2O ( 3), which were structurally characterized by X-ray diffraction. In 1, the square-planar Pt 2+ ion is coordinated to the pyrimidine N(1′), a usual metal-binding site, and three NO 2 − groups. The thiamine molecule exists as a monovalent cation in 1 and a divalent cation in 2 while the TMP molecule is a monovalent cation in 3. In each compound, thiamine or TMP adopts the usual F conformation and forms two types of host–guest-like interactions with anions, which are of the bridging forms, C(2)H⋯anion⋯pyrimidine-ring and N(4′1)H⋯anion⋯thiazolium-ring. In 3, there is an additional anion–bridging interaction between the pyrimidine and thiazolium rings of TMP, being of the form C(6′)H⋯anion⋯thiazolium-ring. The salts 2 and 3 show similar hydrogen-bonded cyclic dimers of thiamine or TMP between which the anions are held. Results are compared with those of the other thiamine–platinum complexes.