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Synthesis, Structures and Electrochemistry of New Carbonylnickel Octacarbide Clusters: The Distorting Action of Carbide Atoms in the Growth of Ni Cages and the First Example of the Inclusion of a Carbon Atom within a (Distorted) Ni Octahedral Cage



The reaction of [Ni10C2(CO)15]2– in thf with a large excess of CdCl2·2.5H2O (8–15 equiv.) resulted in the formation of the new carbonyl octacarbide clusters [H5–nNi36C8(CO)36(Cd2Cl3)]n (n = 3–5), which undergo partial CO replacement to give [Ni36–yC8(CO)34–y(MeCN)3(Cd2Cl3)]3– (y = 0–2) after a prolonged time in MeCN. Treatment of the former with an excess of NaOH afforded the larger [H7–nNi42+yC8(CO)44+y(CdCl)]n (n = 6, 7; y = 0, 1) octacarbides. Their structures (as well as those of the analogous Br-containing clusters) have been fully elucidated by single-crystal X-ray analysis of their [Me4N]5[Ni36C8(CO)36(Cd2Cl3)]·(7–2y)MeCN·yC6H14 (y = 0.40), [Me4N]3[Ni36–yC8(CO)34–y(MeCN)3(Cd2Cl3)]·5MeCN(y = 0.61), [Me4N]7[Ni42+yC8(CO)44+y(CdCl)]·(5–y)MeCN (y = 0.19) and [Me4N]6[HNi42+yC8(CO)44+y(CdBr)]·(6–y)MeCN (y = 0.19) salts, which feature highly distorted metal cages (due to the inclusion of several carbide atoms), and the presence of partially vacant capping Ni(CO) fragments. This aspect, together with the fact that all these species undergo several protonation–deprotonation equilibria in solution as well as reversible redox processes under electrochemical control, indicates that a detailed description of molecular species containing a few dozen metal atoms might be sometimes rather troublesome and non-trivial. A complete elucidation of these systems can be achieved only by combining structural, chemical, spectroscopic, electrochemical and spectroelectrochemical studies.

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