Synthesis of mono-phosphido, mono-dppm bridged Pd(I) cationic dimers. Structure and fluxionality of [Pd-2(mu-P(t)Bu(2))(mu-dppm)(eta(1)-dppm),]CF3SO3 (dppm = bis-diphenylphosphinomethane)

The dimer [Pd-2(mu-(PtBu2)(mu-(PtBu2H)(PtBu2H)2](+)X(-) [(1+)(BF4-), X=BF4; (1)(+)TfO(-), X=CF3SO3], with two terminal and one bridging weakly bonded di-tert-butylphosphine molecule, proved to be an excellent reagent for the preparation of new mono-phosphido, mono-dppm bridged palladium(I) derivatives of general formula [Pd-2(mu-PtBu2)(mu-dppm)(PR3)2](+)X(-) [(2)(+)X(-), PR3 = PtBu2H; (3)(+)X(-), PR3 = PMe3; (4)(+)X(-), PR3 = PEt3; (5)(+)X(-), PR3 = eta(1)-dppm]. The cation (5)(+) has one dppm molecule terminally bonded to each palladium atom in a monodentate fashion. As demonstrated by solution P-31{H-1} NMR spectra, the two phosphorus atoms of each eta(1)-dppm molecule are rapidly scrambled without dissociation through an intermediate chelate coordination of the disphosphine molecule. The same fluxional behavior was observed in the neutral [Pd-2(mu-PtBu2)(mu-dppm)(SPh)(eta(1)-dppm)] (6) obtained by reaction of(5+)(BF4-) with PhSNa. The solid state structures of complexes (3)(+)TfO(-) and (5)(+)TfO(-) were determined by X-ray diffraction methods.