Metal Segregation in Bimetallic CoPd Carbide Carbonyl Clusters: Synthesis, Structure, Reactivity and Electrochemistry of [H Co Pd C (CO) ] (n=3-6).

Nanometric CoPd bimetallic [H Co Pd C (CO) ] (n=3-6) tetracarbide carbonyl clusters have been prepared by redox condensation of [Co C(CO) ] with [PdCl (Et S) ]. The crystal structures of both the dihydride tetra-anion and monohydride penta-anion have been determined as their [NEt ] [H Co Pd C (CO) ]⋅4 CH COCH and [NMe (CH Ph)][NMe ] [HCo Pd C (CO) ]⋅5 CH COCH salts, respectively. The two species are isostructural and their structures display a perfect segregation of the two metals. They are composed of a cubic close-packed (ccp) Pd core stabilised on its surface by four {Co C(CO) } organometallic fragments. Their polyhydride nature has been corroborated by the study of their reactions with acids and bases, and confirmed by electrochemical studies. In addition, the reactions of [H Co Pd C (CO) ] with Na/naphthalene and PPh /CO allowed the isolation of other lower nuclearity homoleptic and heteroleptic clusters, that is, [H Co Pd C (CO) ] (n=5, 6), [Co Pd C(CO) (PPh ) ], [Co Pd C(CO) (PPh ) ], and [Co Pd C (PPh ) (CO) Cl] . [H Co Pd C (CO) ] (n=5, 6) represent the first homoleptic metal-carbonyl clusters containing three interstitial carbide atoms.