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 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 bridgi ng weakly bonded di-tert-butylphosphine molecules, proved to be an exc ellent reagent for the preparation of new mono-phosphido, mono-dppm br idged 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 solu tion P-31{H-1} NMR spectra, the two phosphorus atoms of each eta(1)-dp pm molecule are rapidly scrambled without dissociation through an inte rmediate chelate coordination of the disphosphine molecule. The same f luxional behavior was observed in the neutral [Pd-2(mu-P(t)Bu(2))(mu-d ppm)(SPh)(eta(1) - dppm)] (6) obtained by reaction of(5)(BF4-)-B-+ wit h PhSNa. The solid state structures of complexes (3)(+)Tf(-) and (5)()Tf(-) were determined by X-ray diffraction methods.