Protonation of Platinum(II) Dialkyl Complexes Containing Ligands with Proximate H-Bonding Substituents

The possibility of activating C−H bonds at a platinum(II) center that contains a ligand with a proximate H-bonding functionality, for example a NH2 substituent, has been investigated. A series of platinum(II) dimethyl complexes [Pt(L)Me2], where L is an unsymmetrically substituted bipyridine ligand, has been prepared. Protonation reactions in acetonitrile with 1 equiv of a strong acid generate cationic complexes of the type [Pt(L)Me(CH3CN)]+. The selectivity of the protonation reactions appears to be governed by steric effects rather than H-bonding effects. This is believed to be the result of the low basicity of the amino subsituent in 2-amino pyridines.