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.