Isocyanide-Phosphine Complexes of Palladium(II) Dihalides: Synthesis, Structure, and Resistance to Ligand Disproportionation Reactions

The structure of isocyanide-phosphine complexes of palladium(II) dihalides [PdX2(CNR)(PPh3)] (X = Cl, Br, I; R = t-Bu, Xyl, and Mes) in CDCl3 solutions and in solid phase, and also their resistance to cis/trans isomerization and ligands disproportionation were studied. The isocyanide-phosphine complexes of palladium(II) chloride, bromide, and iodide in crystals take the cis configuration. In solution isocyanide-phosphine complexes of palladium(II) chloride and bromide exist predominantly in the cis configuration. They are resistant to ligand disproportionation and can be prepared by mixing equivalent amounts of the corresponding bisisocyanide and bisphosphine complexes. In contrast, mixed-ligand isocyanide-phosphine complexes of palladium iodide in solution rapidly form mixtures of cis and trans isomers, and also of bisisocyanide and bisphosphine complexes.