Computational study of selectivity in the [Pt^IICl₄]^2--catalysed arylation of arenes by diaryliodonium reagents: Arene activation at Pt^IV centres

The mechanism for the [Pt^IICl₄]^2--catalysed reaction of Ph₂I^III(TFA) (TFA = trifluoroacetate) with naphthalene (NapH) to give β-phenylation over α-phenylation of naphthalene has been examined by computational methods. In support of the mechanism proposed by Sanford based on experimental evidence, reaction commences by oxidative phenyl transfer from [Ph₂I]⁺ to [Pt^IICl₄]^2-, giving trans-[PhPt^IVCl₄(TFA)]^2-. Transformation to cis-[PhPt^IVCl₃(TFA)]^- leads to reaction with NapH at the β-position in an inner-sphere Concerted Metalation Deprotonation (CMD) manner to give cis-[Ph(Nap)Pt^IVCl₃]^- and trifluoroacetic acid. Reductive elimination yields β-PhNap, and coordination of chloride regenerates [Pt^IICl₄]^2- for subsequent catalytic cycles. The selectivity for β-phenylation over α-phenylation is attributable to steric factors in the CMD Pt^IV transition state containing a higher coordination number than that occurring for related reactions in Pd^II catalysis that gives α-phenylation.