Novel coordination behavior of unsaturated hydrocarbon ligands on Pd-Pd bonds

The dinuclear Pd(I) complexes containing substitutionally labile acetonitri le ligands [Pd-2(CH3CN)(2)(L)(2)] (BF4)(2) [L = CH3CN (1), PPh3 (2)] were p repared. The complex 1 was demonstrated to serve as a versatile building bl ock for synthesizing sandwich chain complexes made of conjugated polyenes a nd linear polypalladium chains. The complex 2 reacted with 2 equiv arylacet ylenes to give dinuclear organopalladium complexes arising from formal [2 s igma + 2 pi + 2 pi] addition with the Pd-Pd sigma bond participating as one component. The reaction of 2 with 1,3-butadiene afforded a complex regarde d as an intermediate lying halfway on the [2 sigma + 4 pi] reaction coordin ate.