Synthesis and reactivity of palladium cluster compounds

The synthesis, characterisation and reactions of a new group of palladium clusters are discussed. When [Pd-2(dba)(3)] (dba = dibenzylideneacetone) and PBu3t react in the presence of organic halides CRCl3 (R = H, F) the novel methylidyne cluster compounds [Pd-4(mu(3)-CR)(mu-Cl)(3)(PBu3t)(4)] are obtained. These are the first examples of mu(3)-alkylidyne palladium compounds. They undergo substitution reactions with LiBr and with phosphines (e.g. PCy3) to yield the cluster compounds [Pd-3(mu(3)-CR)(mu- Br)(3)(PBu3t)(4)] with H-2 leads to cluster fragmentation and the capping mu(3)-CF fragment is converted to CFH3. The reaction is an important component of a potential catalytic cycle for the conversion of CFCl3 to CFH3. This reaction is particularly relevant because of the current interest in finding efficient routes to convert CFCs to HFCs. The reactions between [Pd-2(dba)(3)], PBu3t and the organic halides CHX3 (X = Br, I) have also been studied and the dimers [P-2(mu-X)(2)(PBu3t)(2)] have been obtained. Their reactions with CNXyl, H-2, CO, [Co-2(CO)(8)] and [Fe-2(CO)(9)] have been studied and some interesting products have been obtained. The reactions with [Co-2(CO)(8)] have led to the novel heteronuclear clusters [CoPd3(mu(3)-X)(3)(mu-CO)(3)(CO)(2)(PBu3t)(3)] (X = Cl, Br, I). (C) 1998 Elsevier Science S.A. All rights reserved.