Dinuclear [{(π-C3H5)M(PR3)}2(μ-X)]Y complexes of nickel and palladium

The double halide-bridged pi-allyl complexes {(eta(3)-C3H5)M(mu-X)}(2) (M = Ni, Pd; X = Cl, Br) resist halide abstraction by thallium salts of weakly coordinating anions Y = PF6, B(C6F5)(4), and B{C6H3(CF3)(2)}(4) in noncoordinating CH2Cl2. In the presence of a bulky phosphine ((PPr3)-Pr-i, (PBu3)-Bu-t) or when 2 equiv of (eta(3)-C3H5)M(PR3)X is reacted with TlY, one of the halide ions is replaced to afford the ionic dinuclear, single halide-bridged complexes [{(eta(3)-C3H5)M-(PR3)}(2)(mu-X)]Y (M = Ni, X = Br (6, 7); M = Pd, X = Cl (8, 9) and Br (10, 11)), which do not react with further TlY. The corresponding complexes with Y = Al{OC(CF3)(3)}(4) have also been prepared. In addition, it has been found that the dinuclear palladium complexes, but not the nickel derivatives, are also stable for Y = OTf. According to NMR the complexes represent a mixture of diastereomers in solution. For [{(eta(3)-C3H5)Ni((PPr3)-Pr-i)}(2)(mu-Br)] [Al{OC(CF3)(3)}(4)] (6c) and [{(eta(3)-C3H5)Pd((PBu3)-Bu-t)}(2)(mu-Br)] [B(C6F5)(4)] (11b) the crystal structures have been determined. The reaction of (eta(3)-C3H5)M(PMe3)X with TlY affords a mixture of [(eta(3)-C3H5)M(PMe3)(2)]Y (described for M = Ni, Y = PF6 (12) and M = Pd, Y = PF6 (13)) and the starting phosphine-free {(eta(3)-C3H5)M(mu-X)}(2).