Cyclobutadiene–metal Complexes: Part Viii. Synthesis of Tetraphenylcyclobutadiene Nickel Halides by Ligand-Exchange Reactions

The preparation of cyclobutadiene nickel halide complexes (R 4 C 4 NiX 2 ) 2 , where R is phenyl or substituted phenyl, by reaction of the palladium complexes, [R 4 C 4 PdX 2 ] 2 , with a tert-phosphine metal complex, e.g. (n-Bu 3 P) 2 NiX 2 , is described. The reaction proceeds according to the equation[Formula: see text]Possible mechanisms are suggested.