A Cationic Rh(III) Complex That Efficiently Catalyzes Hydrogen Isotope Exchange in Hydrosilanes

The synthesis and structural characterization of a mixed-sandwich (η5-C5Me5)Rh(III) complex of the cyclometalated phosphine PMeXyl2 (Xyl = 2,6-C6H3Me2) with unusual κ4-P,C,C′,C′′ coordination (compound 1-BArf; BArf = B(3,5-C6H3(CF3)2)4) are reported. A reversible κ4 to κ2 change in the binding of the chelating phosphine in cation 1+ induced by dihydrogen and hydrosilanes triggers a highly efficient Si−H/Si−D (or Si−T) exchange applicable to a wide range of hydrosilanes. Catalysis can be carried out in an organic solvent solution or without solvent, with catalyst loadings as low as 0.001 mol %, and the catalyst may be recycled a number of times.