Dihydropentalenes from the palladium(II)-induced cyclotetramerisation of acetylenes; X-ray crystal structures of two dihydropentalenes

Abstract

Phenyl- or p-chlorophenyl-acetylene reacts with [PdL(Bu^tCCHCHCBu^tCl)Cl](L = 2,5-dithiahexane) to give the dihydropentalenes (IIa, R¹= Ph) and (IIb, R¹= C₆H₄Cl-p), which are isostructural with the orange tetramer (Ph₄C₈H₄) obtained from the reaction of phenylactylene with PdCl₂; the structures of (IIb) and of the purple tetramer (Ph₄C₈H₄) also obtained from the latter reaction have been elucidated by X-ray crystallography.