The redox chemistry of [Ni9C(CO)17]2–and [Ni10(C2)(CO)16]2–: Synthesis, electrochemistry and structure of [Ni12C(CO)18]4–and [Ni22(C2)4(CO)28(Et2S)]2–

This paper reports a detailed study of the oxidation and reduction reactions of simple nickel mono-carbide and mono-acetlyde carbonyl clusters. The reduction of [Ni 9 C(CO) 17 ] 2– with Na/naphtalene affords the new [Ni 12 C(CO) 18 ] 4– mono-carbide cluster. Under the same experimental conditions, [Ni 10 (C 2 )(CO) 16 ] 2– reacts with Na/naphtalene yielding a mixture of the previously reported [Ni 11 (C 2 )(CO) 15 ] 4– and [Ni 12 (C 2 )(CO) 16 ] 4– mono-acetylide tetra-anions. The oxidation reactions of both [Ni 9 C(CO) 17 ] 2– and [Ni 10 (C 2 )(CO) 16 ] 2– , carried out with miscellaneous reagents, e.g. , [C 7 H 7 ][BF 4 ], [Cp 2 Fe][PF 6 ], AgNO 3 , are more complicated and less selective, leading to mixtures of products, among which the previously reported [Ni 8 C(CO) 16 ] 2– , [Ni 16 (C 2 ) 2 (CO) 23 ] 4– , [Ni 38 C 6 (CO) 42 ] 6– and [Ni 32 C 6 (CO) 36 ] 6– species have been identified. Interestingly, oxidation of [Ni 10 (C 2 )(CO) 16 ] 2– with Pd(Et 2 S) 2 Cl 2 affords the new tetra-acetylide [Ni 22 (C 2 ) 4 (CO) 28 (Et 2 S)] 2– , even if in low yields. The new species [Ni 12 C(CO) 18 ] 4– and [Ni 22 (C 2 ) 4 (CO) 28 (Et 2 S)] 2– have been structurally characterized by means of single crystal X-ray diffraction. Electrochemical and spectroelectrochemical studies have been performed on [Ni 12 C(CO) 18 ] 4– . This compound can be electrochemically oxidized and reduced reversibly affording [Ni 12 C(CO) 18 ] 3– and [Ni 12 C(CO) 18 ] 5– , respectively. The same species can be obtained by chemical methods but, due to their limited stability during work-up, it has not been possible to isolate them.