INSERTION OF ACETYLENES IN THE PD-PD BOND OF PD2(PH2PCH2PPH2)2CL2

Dimethylacetylene dicarboxylate and hexafluoro-2-butyne add to Pd2(dpm)2Cl2 (dpm = Ph2PCH2PPh2) to give crystalline adducts Pd2(dp)2(μ-acetylene)Cl2. An X-ray crystal structure of Pd2(dpm)2(μ-C4F6)Cl2 reveals that the acetylene has inserted into the metalmetal bond and has been transformed into a cis-dimetallated olefin. The central CC bond length of the bridging olefin is 1.338(16) Å. The coordination about each of the two similar palladium ions is planar and involves two trans-phosphines (one from each of the bridging dpm ligands), a terminal chloride, and one carbon of the bridging olefin. Both Pd2(dpm)2Cl2 and Pd2(dpm)2(μ-C2{CO2H3}2)Cl2 catalyze the cyclotrimerization of dimethyl-acetylene dicarboxylate. © 1979.