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 equals bis-diphenylphosphinomethane)

The dimer [Pd-2(mu-(PBU2)-B-t)(mu-(PBU2H)-B-t)((PBU2H)-B-t)(2)](+)X(-) [(1)(BF4-)-B-+, X=BF4; (1)(+)Tf(-), X=CF3SO3], with two terminal and one bridging weakly bonded di-tert-butylphosphine molecules, 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-P(t)Bu(2))(mu-dppm)(PR(3))(2)](+)X(-) [(2)(+)X(-), PR(3) = P(t)Bu(2)H; (3)(+)X(-), PR(3) = PMe(3); (4)(+)X(-), PR(3) = PEt(3); (5)(+)X(-), PR(3) = 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-P(t)Bu(2))(mu-dppm)(SPh)(eta(1) - dppm)] (6) obtained by reaction of(5)(BF4-)-B-+ with PhSNa. The solid state structures of complexes (3)(+)Tf(-) and (5)(+)Tf(-) were determined by X-ray diffraction methods.