(DIHALOMETHYL)PALLADIUM(II) COMPLEXES FROM PALLADIUM(0) PRECURSORS OF DIBENZYLIDENE ACETONE - SYNTHESIS, STRUCTURAL CHEMISTRY AND REACTIVITY

Bis(dibenzylideneacetone)palladium(0) (1) reacts with one equivalent of a chelating phosphine ligand (P-P) or two equivalents of a monophosphine ligand (P) to give complexes of the type (P-P)Pd(dba) (3a-c; dba = dibenzylidene acetone) and (P)(2)Pd(dba) (3d,e) respectively, that have been characterized spectroscopically and structurally (X-ray structure analysis). These complexes readily cleave the carbon-halogen bond of chloroform or bromoform. The air- and moisture-stable oxidative addition products (P-P)Pd(CHX(2))X (4a-d; X = Cl, Br) are thus obtained in 70-85% yield. Their identity was established by a single-crystal X-ray diffraction study of 4a.