Protonation of platinum(II) pyrazolates: synthesis, characterization and X-ray crystal structure of [Pt(dppe)(Hpz-N)(2)][BF4](2)center dot CHCl3 center dot H2O (Hpz-N = unsubstituted pyrazole)

Protonation reactions of [Pt(dppe)(pz-N)(2)] (1) carried out either with HBF4(aq) or with [18-crown-6 .H3O][BF4], afford the new pyrazole adduct [Pt(dppe)(Hpz-N)(2)][BF4](2) (3) characterized by analytical, infrared and multinuclear NMR data. Deprotonation of 3 as well as protonation of 1, under controlled conditions, give the known binuclear Pt(II) pyrazolato complex [Pt(dppe)(mu -pz-N,N'](2)[BF4](2) (2). Competitive formation of mono-, 3, and dinuclear, 2, compounds is discussed. The structure of a solvate of complex 3, (C33H35B2N4OF8Cl3P2Pt), was solved by X-ray diffraction. The platinum atom exhibits a distorted square-planar geometry (P-Pt-P angle 85.3(1)degrees and N-Pt-N angle 87.0(4)degrees). The geometry around the B atom is tetrahedral. The hydrogen bonds between the pyrazole rings and one BF4- orientate the pyrazoles roughly in the same direction, away from the coordination plane. (C) 2001 Published by Elsevier Science Ltd.