REACTIONS OF PALLADIUM COMPOUNDS WITH ACETYLENES: II. TETRAKIS(<i>p</i>-CHLOROPHENYL)CYCLOBUTADIENE PALLADIUM COMPLEXES

Abstract

It is found that both diphenylacetylene and bis(p-chlorophenyl)acetylene on reaction with bis(benzonitrile)palladium chloride in benzene give the benzenoid trimer (R 6 C 6 ) as well as a new type of cyclobutadiene complex [(R 4 C 4 )(PdCl 2 ) x ] 2 (R = Ph and p-ClC 6 H 4 ) for which structure IV is proposed. p,p′-Dichlorotolan reacts with bis(benzonitrile)palladium chloride in ethanol – methylene chloride to give a complex [(R 4 C 4 OC 2 H 5 )PdCl] 2 (II) which is converted into the normal cyclobutadiene complex [(R 4 C 4 )PdBr 2 ] 2 (V) on treatment with hydrogen bromide. This can also be obtained from IV. The tetrakis(p-chlorophenyl)cyclobutadiene palladium halides on treatment with tri-n-butylphosphine give a dimer of tetrakis(p-chloro-phenyl)cyclobutadiene which is probably octakis(p-chlorophenyl)cyclooctatetraene. Tetrakis-(p-chlorophenyl)cyclobutadiene iron tricarbonyl has also been prepared from IV and V by a ligand-transfer reaction.