Computational study of selectivity in the [PtIICl4]2−-catalysed arylation of arenes by diaryliodonium reagents: arene activation at PtIV centres

The mechanism for the [PtIICl4]2−-catalysed reaction of Ph2IIII(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 [PtIICl4]2−, giving trans-[PhPtIVCl4(TFA)]2−. Transformation to cis-[PhPtIVCl3(TFA)]− leads to reaction with NapH at the β-position in an inner-sphere Concerted Metalation Deprotonation (CMD) manner to give cis-[Ph(Nap)PtIVCl3]− and trifluoroacetic acid. Reductive elimination yields β-PhNap, and coordination of chloride regenerates [PtIICl4]2− for subsequent catalytic cycles. The selectivity for β-phenylation over α-phenylation is attributable to steric factors in the CMD PtIV transition state containing a higher coordination number than that occurring for related reactions in PdII catalysis that gives α-phenylation