Palladium complexes of bridgehead phosphines

Abstract

Palladium chloro complexes reacted with 9-phenyl-9-phosphabicyclononanes (PPBN) and 1-phenylphospholane and gave trans-chlorobis(phosphine)palladium(II) complexes, 1-phenylphospholane also gave rise to a chloro-bridged dimer. With palladium acetate, the two isomers of PPBN (9-phenyl-9-phosphabicyclo-[3.3.1]nonane and-[4.2.1]nonane, 3,3,1-PPBN and 4,2,1-PPBN respectively) formed trans bis(phosphine) complexes exclusively whereas 1-phenylphospholane formed the cis-bis(phosphine) complex; examples of both trans and cis complexes have been structurally characterised. The acetate groups were readily replaced by sulfonic and phosphonic acids to give sulfonato and phosphonato complexes respectively. Reduction of the acetato–4,2,1-PPBN complex to [Pd ⁰ (4,2,1-PPBN) ₃ ] occurred in alcoholic media readily, however the isomeric 3,3,1-PPBN complex was considerably more resistant to reduction. Abstraction of halide from both dichloro–PPBN complexes by Ag(O ₃ SCF ₃ ) in ethanol resulted in the formation of phosphonium salts.