An unusual product distribution from the reaction of Pd(η3-1-PhC3H4)(η5-C5H5) with a deficiency of PPh3 in the presence of bromobenzene

Reactions of Pd(η3-1-PhC3H4)(η5-C5H5) (I) with PPh3 (1:1 ratio) in the presence of excess bromobenzene result in the formation of Pd(η5-C5H5)(η1-PhC3H4)(PPh3) (II), syn- and anti-isomers of the dinuclear species Pd2L2(μ-C5H5)(μ-PhC3H4) (IIIa, b), the phenyl compound PdPh(η5-C5H5)(PPh3) (IV), the dinuclear species Pd2L2(μ-Br)(μ-anti-PhC3H4) (V) and an organic compound, trans-1,3-diphenylpropene. Not observed are trans-PdBrPh(PPh3)2 and [PdBrPh(PPh3)]2, the anticipated products of oxidative addition of bromobenzene to Pd(0)–PPh3 species, and thus, the types of products formed are generally very different from those obtained elsewhere with other phosphines. Compounds IV and V are found to be very stable at high temperature and to be relatively poor catalysts for e.g., the amination of bromoanisole by morpholine in the presence of sodium t-butoxide.