Synthesis and chemistry of some palladacyclopentanes

Abstract

The palladacyclopentane complexes [P[graphic omitted]H₂)L₂][(1) L₂= 1,2-bis(diphenylphosphino)ethane(dppe); (2) L₂=NNN′N′-tetramethylethylenediamine(tmen)] have been prepared by reaction of the corresponding dichlorides with an ether solution of 1,4-dilithiobutane. Compound (2) participates in substitution reactions of tmen with various ligands [dppe, 2,2′-bipyridyl (bipy), or PPh₃] affording (1), [P[graphic omitted]H₂)(bipy)](3), and [[graphic omitted]H₂)(PPh₃)₂](4) respectively. The palladium–carbon bonds of these compounds are easily cleaved by HCl and Br₂ to given n-butane and 1,4-dibromobutane as the organic products. Treatment of (1) with CO does not result in carbonylation products; by contrast, (2)–(4) react to give cyclopentanone. Compound (1) and some isostructural linear palladium dialkyls react with SO₂ to give corresponding S-bonded disulphinates. Compounds (1), (3), and (4) undergo ready hydride abstraction by the trityl cation to give the η³-1-Methylallyl complexes, [Pd(η³-CH₂CHCHMe)L₂][BF₄].