Reversible Inter- and Intramolecular Carbon–Hydrogen
Activation, Hydrogen Addition,
and Catalysis by the Unsaturated Complex Pt(IPr)(SnBu<sup>t</sup><sub>3</sub>)(H)
The
complex Pt(IPr)(SnBu<sup>t</sup><sub>3</sub>)(H) (<b>1</b>)
was obtained from the reaction of Pt(COD)<sub>2</sub> with Bu<sup>t</sup><sub>3</sub>SnH and IPr [IPr = <i>N</i>,<i>N</i>′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene].
Complex <b>1</b> undergoes exchange reactions with deuterated
solvents (C<sub>6</sub>D<sub>6</sub>, toluene-<i>d</i><sub>8</sub>, and CD<sub>2</sub>Cl<sub>2</sub>), where the hydride ligand
and the methyl hydrogen atoms on the isopropyl group of the IPr ligand
have been replaced by deuterium atoms. Complex <b>1</b> reacts
with H<sub>2</sub> gas reversibly at room temperature to yield the
complex Pt(IPr)(SnBu<sup>t</sup><sub>3</sub>)(H)<sub>3</sub> (<b>2</b>). Complex <b>2</b> also undergoes exchange reactions
with deuterated solvents as in <b>1</b> to deuterate the hydride
ligands and the methyl hydrogen atoms on the isopropyl group of the
IPr ligand. Complex <b>1</b> catalyzes the hydrogenation of
styrene to ethylbenzene at room temperature. The reaction of <b>1</b> with 1 equiv of styrene at −20 °C yields the
η<sup>2</sup>-coordinated product Pt(IPr)(SnBu<sup>t</sup><sub>3</sub>)(η<sup>2</sup>-CH<sub>2</sub>CHPh)(H) (<b>3</b>), and with 2 equiv of styrene, it forms Pt(IPr)(η<sup>2</sup>-CH<sub>2</sub>CHPh)<sub>2</sub> (<b>4</b>)
