Insertion and β-Hydride Elimination Reactions of Ruthenium/Zirconium Complexes Containing C₂ Bridges with Bond Orders of 1, 2, and 3

Carbon dioxide inserts into the Zr-C bond of Cp(PMe₃)₂RuCH═CHZrClCp₂, producing the carboxylate complex Cp(PMe₃)₂RuCH═CHCO₂ZrClCp₂. An η²-iminoacyl insertion product, Cp(PMe₃)₂Ru—C≡C-C(N^tBu)ZrClCp₂, results from insertion of ^tBuNC into the Zr-C bond of the dimetalloalkyne complex Cp(PMe₃)₂Ru—C≡C—ZrClCp₂. The reaction of Cp(PMe₃)₂RuCH₂CH₂ZrClCp₂with high concentrations of ^tBuNC also produces an η²-immoacyl insertion product, Cp(PMe₃) ₂RuCH₂CH₂C(N^tBu)ZrClCp₂. At low concentrations of ^tBuNC, a competing reaction is β-hydride elimination from Cp(PMe₃)₂RuCH₂CH₂ZrClCp₂to give Cp(PMe₃)₂RuCH=CH ₂and Cp₂Zr(H)Cl, which is trapped by ^tBuNC under these conditions to give Cp₂ZrCl(η²-^tBuN=CH). The reaction of benzophenone with Cp(PMe₃)₂RuCH₂CH₂ZrClCp₂gives the insertion product Cp(PMe₃)₂RuCH₂CH₂CPh₂OZrClCp₂. β-Hydride elimination is also observed from Cp(PMe₃)₂RuCH═CHZrClCp₂; in the presence of excess ⁿBuC═CH, the products are Cp(PMe₃)₂Ru— C≡C—H and the zirconium vinyl complex Cp₂Zr(Cl)CH═CHⁿBu.