Metal Segregation in Bimetallic CoPd Carbide Carbonyl Clusters: Synthesis, Structure, Reactivity and Electrochemistry of [H 6− n Co 20 Pd 16 C 4 (CO) 48 ] n − ( n =3–6)

Nanometric CoPd bimetallic [H 6− n Co 20 Pd 16 C 4 (CO) 48 ] n − ( n =3–6) tetracarbide carbonyl clusters have been prepared by redox condensation of [Co 6 C(CO) 15 ] 2− with [PdCl 2 (Et 2 S) 2 ]. The crystal structures of both the dihydride tetra‐anion and monohydride penta‐anion have been determined as their [NEt 4 ] 4 [H 2 Co 20 Pd 16 C 4 (CO) 48 ] ⋅ 4 CH 3 COCH 3 and [NMe 3 (CH 2 Ph)][NMe 4 ] 4 [HCo 20 Pd 16 C 4 (CO) 48 ] ⋅ 5 CH 3 COCH 3 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 16 core stabilised on its surface by four {Co 5 C(CO) 12 } 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 2 Co 20 Pd 16 C 4 (CO) 48 ] 4− with Na/naphthalene and PPh 3 /CO allowed the isolation of other lower nuclearity homoleptic and heteroleptic clusters, that is, [H 6− n Co 16 Pd 2 C 3 (CO) 28 ] n − ( n =5, 6), [Co 4 Pd 2 C(CO) 11 (PPh 3 ) 2 ], [Co 2 Pd 5 C(CO) 8 (PPh 3 ) 5 ], and [Co 4 Pd 4 C 2 (PPh 3 ) 4 (CO) 10 Cl] − . [H 6− n Co 16 Pd 2 C 3 (CO) 28 ] n − ( n =5, 6) represent the first homoleptic metal–carbonyl clusters containing three interstitial carbide atoms.