STRUCTURAL STUDIES OF COMPLEXES CONTAINING CYCLOPLATINATED TRIS(PYRAZOL-1-YL)METHANE

Cyclometallation at the C(5) position of one ring of tris(pyrazol-1-yl)methane occurs on dissolution of PtMe2{(pz)3CH} in 3,5-dimethylpyridine, to form the platinum(II) complex PtMe{(pz)2(C3H2N2)-CH-N,C}(3,5-Me2py) (1b). Structural studies of 1b, and the related complexes PtMe{(pz)2(C3H2N2)-CH-N,C}(N-methylimidazole) (1c) and PtMe{(pz)2(C3H2N2)CH-N,C}{PPh2(o-MeOC6H4)} (1d) show that these complexes have square planar geometry with cis-organic groups, with the cyclometallated group having one pyrazole ring uncoordinated. The complexes PtMe{(pz)2(C3H2N2)CH-C}(L2) [L2 = 2PPh3 (2a), 2PEtPh2 (2b), Ph2PCH2CH2PPh2 (2c)] have a similar geometry at platinum(II); the metallated ligand is present as a [C]- donor with two uncoordinated pyrazole rings. In 2a, 2b, and 2c, there are short Pt...H contacts at approximately 2.7 angstrom for the methine proton of the cyclometallated ligand.