Metal ion and anion coordination in the thiamine–[PtII(NO2)4]2− system. Structures of a metal complex, Pt(thiamine)(NO2)3, and two salts, (H-thiamine)[Pt(NO2)4]·2H2O and (thiamine monophosphate)2[Pt(NO2)4]·2H2O

Reaction of thiamine or thiamine monophosphate (TMP) with K2Pt(NO2)4 afforded a metal complex, Pt(thiamine)(NO2)3 (1), and two salt-type compounds, (H-thiamine)[Pt(NO2)4]·2H2O (2) and (TMP)2[Pt(NO2)4]·2H2O (3), which were structurally characterized by X-ray diffraction. In 1, the square-planar Pt2+ ion is coordinated to the pyrimidine N(1′), a usual metal-binding site, and three NO2 − 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.