Synthesis, characterization, and C–H/C–C cleavage reactions of two rhodium–trispyrazolylborate dihydrides

Treatment of Tp′Rh(PMe3)Cl2 and Tp′Rh(CNCH2CMe3)Cl2 with Cp2ZrH2 produces Tp′Rh(PMe3)H2 and Tp′Rh(CNCH2CMe3)H2, respectively, in excellent yield. Photolysis of benzene solutions of each dihydride complex generates hydrogen and the fragment [Tp′Rh(L)] which inserts into the solvent C–H bond. The phosphine dihydride has also been shown to be a catalyst for the hydrogenation of biphenylene, showing a capability to cleave C–C bonds. Reductive elimination of benzene from Tp′Rh(PMe3)PhH is nearly 250 times slower than from Cp*Rh(PMe3)PhH.