Cage Rearrangements in Dodecanuclear Co–Pt Dicarbido Clusters Promoted by Redox Reactions

Abstract

The chemical reduction of [Co 8 Pt 4 C 2 (CO) 24 ] 2-([1] 2-) with Na/ naphthalene results, after workup, in the isolation of either [Co 10 Pt 2 C 2 (CO) 22 ] 4-([2] 4-) or [Co 8 Pt 4 C 2 (CO) 20 ] 4-([3] 4-), depending on the experimental conditions. All these species undergo several chemical and/or electrochemical redox reactions, disclosing the existence of structurally related dodecanuclear clusters [1] n-(n = 0-4), [2] n-(n = 2-6) and [3] n-(n = 1-7). In the attempt to isolate more reduced species,[a]

Bimetallic Nickel–Cobalt Hexacarbido Carbonyl Clusters [H6–nNi22Co6C6(CO)36]n−(n= 3–6) Possessing Polyhydride Nature and Their Base-Induced Degradation to the Monoacetylide [Ni9CoC2(CO)16–x]3–(x= 0, 1)

“…Such a suggestion is further implemented by electrochemical studies, which clearly point out that [H 2 Ni 22 Co 6 C 6 (CO) 36 ] 4– and [HNi 22 Co 6 C 6 (CO) 36 ] 5– display different voltammetric profiles. If they were the same species in a different oxidation state, they would have, conversely, shown the same electrochemical behavior, as previously discussed. ,− In particular, [H 2 Ni 22 Co 6 C 6 (CO) 36 ] 4– displays two reduction processes with features of chemical reversibility ( E °′ 4–/5– = −0.533 V; E °′ 5–/6– = −0.833 V, in acetone), whereas [HNi 22 Co 6 C 6 (CO) 36 ] 5– displays three reductions ( E °′ 5–/6– = −0.961 V; E °′ 6–/7– = −1.293 V; E °′ 7–/8– = −1.666 V, in CH 3 CN). Therefore, the changes in ν(CO) reported in Scheme cannot be due to redox reactions.…”

“…In addition, joined electrochemical and chemical experiments result as being the only tools available to elucidate the polyhydride nature of such large carbonyl clusters, since their hydride atoms are 1 H NMR silent. This point has already been discussed in the literature, even if a satisfactory explanation of this phenomenon is still missing. ,− …”

“…We have recently discussed the problems of detecting hydrides in high-nuclearity carbonyl clusters, showing that above a nuclearity of ca. 22 all 1 H NMR resonances disappear since they become so broad as to get blurred in the baseline of the spectrum. ,− Thus, as already reported, the hydride nature of large metal carbonyl clusters can be only indirectly inferred from joined chemical and electrochemical experiments.…”

Metal Segregation in Bimetallic CoPd Carbide Carbonyl Clusters: Synthesis, Structure, Reactivity and Electrochemistry of [H6−nCo20Pd16C4(CO)48]n− (n=3–6)

“…The C 2 ‐acetylide fragment of [Co 4 Pd 4 C 2 (PPh 3 ) 4 (CO) 10 Cl] − is semiexposed in view of the fact that the metal cage is rather open. It must be remarked that several homoleptic MCCs containing fully interstitial C 2 units are known, with C–C contacts in the range 1.35–1.50 Å 17b, 29. Homoleptic MCCs containing semiexposed acetylide fragments are more rare.…”

Intermetalloid and Heterometallic Clusters Combining p-Block (Semi)Metals with d- or f-Block Metals

“…Viewed another way, the encapsulated transition metal atoms have a full 18-electron shell: 10 e – from Ni 0 and 2 e – each from each neighboring main group atom in the square antiprismatic pocket. The structure of [Ni 2 @Sn 7 Bi 5 ] 3– is related to a family of carbide-centered transition metal–carbonyl clusters (e.g., [C 2 @Rh 12 (CO) 24 ] 2– ) − as well as structural motifs found in the solid state, such as in Ir 3 E 7 (E = Ge, Sn) and FeBi 2 . − …”