Platinum complexes with N-N-C ligands. Syntheses, electrochemical and spectroscopic characterizations of Pt(II) and electrogenerated, formal Pt(I) species

A series of cyclometallated platinum(II) species with NNC ligands (NNCortho-C-deprotonated form of 6-benzyl-substituted 2,2%-bipyridines) and different fourth monodentate ligands (Cl, I, CN, CO, PPh3, Py, MeCN) has been investigated electrochemically, with particular emphasis to the analysis of the relatively stable one-electron reduced species. EPR spectra have been recorded at different temperatures on the electroreduced solutions. The analyses were supported by a systematic comparison with simulated spectra and allowed a definition of the interaction of the additional unpaired electron with the 195Pt, 14N, and 1H nuclei present in the molecule. Attention has been also paid to the effects of the ligands on the thermodynamics (E1:2,r) of the reduction, as well as to some reactivity aspects of the substrates that could be shown by voltammetric tests. A number of these compounds have been synthesised for the first time, so that a full characterisation has been performed.