Axial Shielding of 5d8 and 5d7 Metal Centers in Dimesitylplatinum Complexes with Unsaturated Chelate Ligands: Spectroscopic and Spectroelectrochemical Studies of Four Different Oxidation States. Organometallics, (14)3:1176--1186, 1995. [PUMA: axial bipyrazine complex complex;bipyridine complex;bipyrimidine complex;dimesitylplatinum complex;dipyridophenazine complex;platinum complex;shielding complex;tetraazaphenanthrene complex;valence diimine dimesityl dimesitylplatinum]