Alkyl Carbon−Nitrogen Reductive Elimination from Platinum(IV)−Sulfonamide Complexes

Platinum(IV) complexes containing monodentate sulfonamide ligands, fac-(dppbz)PtMe3(NHSO2R)
(dppbz = o-bis(diphenylphosphino)benzene; R = p-C6H4(CH2)3CH3 (1a), p-C6H4CH3 (1b), CH3 (1c)), have
been synthesized and characterized, and their thermal reactivity has been explored. Compounds 1a−c
undergo competitive C−N and C−C reductive elimination upon thermolysis to form N-methylsulfonamides
and ethane, respectively. Selectivity for either C−N or C−C bond formation can be achieved by altering
the reaction conditions. Good yields of the C−N-coupled products were observed when the thermolyses
of 1a−c were conducted in benzene-d6. In contrast, exclusive C−C reductive elimination occurred upon
themolysis of 1a,b in nitrobenzene-d5. When the thermolyses of 1a were performed in the presence of
sulfonamide anion NHSO2R- in benzene-d6, ethane elimination was completely inhibited and C−N reductive
elimination products were formed in high yield. Mechanistic studies support a two-step reaction pathway
involving initial dissociation of NHSO2R- from the platinum center, followed by nucleophilic attack of this
anion on a methyl group of the resulting five-coordinate platinum(IV) cation to form MeNHSO2R and (dppbz)PtMe2. C−C reductive elimination to form ethane occurs directly from the five-coordinate Pt(IV) cation.