Thermolysis of the five-coordinate Pt(IV) complex (AnIm) Pt(CH3)(3) (1b) (AnIm = [o-C6H4{N (C6H3 Pr-i(2))}(CH = NC6H3 Pr-i(2))](-)) in benzene-d(6) at 60 degrees C yields a new Pt(II) olefin hydride complex (2b-d(27)). For the AnIm complexes and their nacnac analogues, intermolecular arene C-H bond activation is found to be faster than intramolecular - hydride elimination at 60 C. In contrast, intermolecular alkane activation is slow relative to - hydride elimination at 60 C. Although AnIm and nacnac complexes have similar structures and spectral features, modification of the bidentate nitrogen ligand backbone from nacnac to AnIm dramatically increases the rate of ethane reductive elimination from the five-coordinate platinum(IV) complex and decreases the rate of olefin insertion at the platinum( II) olefin hydride complex.