SYNTHESIS OF PALLADIUM DIMERS BRIDGED BY A RANGE OF PHOSPHINOCYCLOPENTADIENYL LIGANDS

The reaction of [PdClMe(cod)] or [Pd-2(mu-Cl)(2)Me(2)(AsPh(3))(2)] wit h TlC(5)H(4)PPh(2) yields the dppc-bridged complex [Pd(2)Me(2)(mu-eta( 5)-C(5)H(4)PPh(2))(2)]. The compound crystallizes in the monoclinic sp ace group P2(1)/c with a = 10.511(5) Angstrom, b = 19.848(8) Angstrom, c = 14.933(5) Angstrom, beta = 100.31(3)degrees, V = 3065(2) Angstrom (3), and Z = 4. Least-squares refinement converged at R = 0.0468 and R (w) = 0.0614, based on 7202 reflections with F > 4.0 sigma(F). Analogo us reactions of [Pd-2(mu-Cl)(2)R(2)(AsPh(3))(2)] (R = Et, Ph, COMe) wi th TIC(5)H(4)PPh(2) generate [Pd(2)R(2)(mu-eta(5)-C(5)H(4)PPh(2))(2)]. Similarly, dimethylcyclopentadienyl complexes may be prepared by reac tion of [Pd-2(mu-Cl)(2)-Me(2)(NC(5)H(3)Me(2)-2,6)] or [Pd-2(mu-Cl)(2)P h(2)(AsPh(3))(2)] with TlC(5)H(4)PMe(2). Reactions of [PdClMe-(cod)] w ith TlC5H4P(OEt)(2), or [Pd-2(mu-Cl)(2)Me(2)(AsPh(3))(2)] with LiC(5)M e(4)PPh(2), further extend the range of phosphinocyclopentadienyl-brid ged palladium complexes. In each case, their NMR spectra indicate that , in contrast to their platinum analogues, they adopt symmetrical, eta (5)-cyclopentadienyl structures in solution. On standing in solution, the compounds [Pd(2)Me(2)(mu-eta(5)-C(5)H(4)PR(2))(2)] (R = Me, OEt) u ndergo coupling of the methyl and phosphino groups, and loss of pallad ium, to yield C(5)H(4)PR(2)Me, each of which has also been prepared fr om TlC5H4-PR(2) and iodomethane.