Synthesis and Catalytic Properties of a Carbometalated Half-Sandwich Ru(II) Complex Bearing a Rigid Polyaromatic Tether

We describe the synthesis and catalytic studies of a prototypical coordinatively rigid carbometalated half-sandwich Ru(II) complex bearing a rigid polyaromatic tether. This compound represents a rare example of the nonplanar pincer complex with an unusual coordination environment. Despite being coordinatively and electronically saturated, the carbometalated complex showed the ability to activate and transfer hydrogen to polar and nonpolar double bonds. The catalytic activity of the complex was benchmarked in the Ru-catalyzed chemoselective hydrogenation of α,β-unsaturated ketones. Our initial mechanistic studies indicate that the hydrogenation is operated via an inner-sphere mechanism that proceeds via dihydride intermediates.