Reversible Inter- and Intramolecular Carbon-Hydrogen Activation, Hydrogen Addition, and Catalysis by the Unsaturated Complex Pt(IPr)(SnBu^t ₃)(H)

The complex Pt(IPr)(SnBu^t ₃)(H) (1) was obtained from the reaction of Pt(COD)₂ with Bu^t ₃SnH and IPr [IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Complex 1 undergoes exchange reactions with deuterated solvents (C₆D₆, toluene-d₈, and CD₂Cl₂), where the hydride ligand and the methyl hydrogen atoms on the isopropyl group of the IPr ligand have been replaced by deuterium atoms. Complex 1 reacts with H₂ gas reversibly at room temperature to yield the complex Pt(IPr)(SnBu^t ₃)(H)₃ (2). Complex 2 also undergoes exchange reactions with deuterated solvents as in 1 to deuterate the hydride ligands and the methyl hydrogen atoms on the isopropyl group of the IPr ligand. Complex 1 catalyzes the hydrogenation of styrene to ethylbenzene at room temperature. The reaction of 1 with 1 equiv of styrene at -20°C yields the η²-coordinated product Pt(IPr)(SnBu^t ₃)(η²-CH₂CHPh)(H) (3), and with 2 equiv of styrene, it forms Pt(IPr)(η²-CH₂CHPh)₂ (4).