Mechanism of Dihydrogen Splitting by An Apparent Bimetallic Frustrated Lewis Pair based on Ir(III)/Pt(0)

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 [(eta(5)-C5Me5)IrCl(PMe2ArDipp2)](+) (Ar-Dipp2=C6H3-2,6-(C6H3-2,6-Pr-i(2))(2)) with the Lewis basic Pt(0) compound Pt((PBu3)-Bu-t)(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 [(eta(5)-C5Me5)Ir(Cl)(H)(PMe2ArDipp2)] and [PtH((PBu3)-Bu-t)(2)](+) are rapidly formed, which suggests an actual FLP mechanism operating. However, our in-depth 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 Bronsted catalyzed hydrogenation of the Pt(0) precursor.

Automated summary

The combination of Lewis acidic Ir(III) cation and Lewis basic Pt(0) compound offers potential for bond activation and catalysis. The study uncovers a cooperative cleavage reaction of dihydrogen and provides evidence for a synergistic route rather than a genuine FLP-type activation. The whole process involves equilibrium processes and the Bronsted catalyzed hydrogenation.