Synthesis, characterization, and fluxional behaviour of binuclear palladium complexes with a half-a-frame structure

Partial removal of chloride anions from the dimer [Pd(eta (3)-2-CH3-C3H4)(m u -Cl)](2) with AgTf(Tf = CF3SO3) followed by addition of dppm affords [Pd- 2(eta (3) -Me-C3H4)(2)(mu -Cl)(mu -dppm)]Tf (1). The substitution of Cl- by X- (X = pz, SC6F5, S-py) using the appropriate salts yields the new deriva tives [Pd-2(eta (3)-Me-C3H4)(2)(mu -X)(mu -dppm)]Tf (2-4). All complexes ex hibit a dinuclear half-A-frame structure with two isomers present in soluti on. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperat ure H-1 NMR spectroscopy. The molecular structures of 2 and 4 were solved b y X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases.