Dedicated to Douglas Stephan on the occasion of his 70th birthday.The incorporation of transition metals into frustrated Lewis pairs (FLPs) offers multiple opportunities for bond activation and catalysis. In this work, we explore the combination of the Lewis acidic Ir(III) cation [(η 5 -C 5 Me 5 )IrCl(PMe 2 Ar Dipp2 )]with the Lewis basic Pt(0) compound Pt(P t Bu 3 ) 2 . The bulkiness of the phosphine ligands prevents the formation of a bimetallic adduct. We have explored the cooperative cleavage of dihydrogen to gauge bimetallic FLP reactivity.As anticipated, compounds [(η 5 -C 5 Me 5 )Ir-(Cl)(H)(PMe 2 Ar Dipp2 )] and [PtH(P t Bu 3 ) 2 ] + are rapidly formed, which suggests an actual FLP mechanism operating. However, our indepth experimental/computational study evidences that the whole process is considerably more complicated. Instead of a genuine FLP-type activation, we favor a synergistic route that entails a number of equilibrium processes and the Brønsted catalyzed hydrogenation of the Pt(0) precursor.

The divergent reactivity of the cationic iridium complex [(η5-C5Me5)­IrCl­(PMe2ArDipp2)]+ (ArDipp2 = C6H3–2,6-(C6H3–2,6- i Pr2)2) toward organolithium and Grignard reagents is described. The noninnocent behavior of the Cp* ligand, a robust spectator in the majority of stoichiometric and catalytic reactions, was manifested by its unforeseen electrophilic character toward organolithium reagents LiMe, LiEt, and Li n Bu. In these unconventional transformations, the metal center is only indirectly involved by means of the Ir­(III)/Ir­(I) redox cycle. In the presence of less nucleophilic organolithium reagents, the Cp* ligand also exhibits noninnocent behavior undergoing facile deprotonation, which is also concomitant with the reduction of the metal center. In turn, the weaker alkylating agents EtMgBr and MeMgBr effectively achieve the alkylation of the metal center. These reactive iridium­(III) alkyls partake in subsequent reactions: while the ethyl complex undergoes β-H elimination, the methyl derivative releases methane by a remote C–H bond activation. Computational studies, including the quantum theory of atoms in molecules (QTAIM), support that the preferential activation of the non-benzylic C–H bonds takes place via sigma-bond metathesis.