C–H and C–C Bond Formation Promoted by Facile κ3/κ2 Interconversions in a Hemilabile “Click”-Triazole Scorpionate Platinum System

A series of platinum complexes bearing 3-fold symmetrical “Click”-triazole-based scorpionate ligands (TtR) has been prepared. Metalation of these weakly donating ligands results in neutral Pt­(II) complexes that display a κ2 coordination mode. Such complexes are susceptible to oxidative addition using a variety of electrophilic alkyl and allyl reagents to generate isolable cationic κ3 Pt­(IV) complexes. Protonation of the κ2 precursors results in Pt­(IV) dimethyl hydride cations. Thermolysis of the dimethyl hydride species at 35 °C in the presence of a trapping π-acid ligand initiates reductive elimination of methane and formation of a Pt­(II) species of the type [TtPhPtMe­(L)]­[BF4] (L  CO, ethylene, propylene, cis-2-butene, trans-2-butene, isobutylene) in good yield. Furthermore, the κ3 σ-allyl complexes [TtRPt­(Ph)2(CH2CHCH2)]­[I] cleanly undergo Csp2–Csp2 reductive coupling to form biphenyl at ambient temperatures. The TtR ligand serves as a homofunctional hemilabile ligand and exhibits a lower barrier κ3/κ2 interconversion to generate reactive unsaturated five-coordinate complexes than the well-studied Tp′PtMe2H complex, which requires thermolysis at temperatures above 100 °C.