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

The chemical reduction of [Co8Pt4C2(CO)24]2– ([1]2–) with Na/ naphthalene results, after workup, in the isolation of either [Co10Pt2C2(CO)22]4– ([2]4–) or [Co8Pt4C2(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, 1. Introduction Dimetallic and heteronuclear Metal Carbonyl Clusters (MCCs) are interesting both as molecular species and as precursors of metal nanoparticles. In the latter case, the use of a dimetallic molecular precursor enables the preparation of dimetallic nanoparticles with well-defined compositions.[ 1–4] At the molecular level, the synergic effect of two metals with complementary properties and/or the stabilising effect of an interstitial heteroelement results in larger and more stable molecular MCCs.[5,6] Indeed, the largest homoleptic MCC reported to date is the dimetallic cluster [Ni32Pt24(CO)56]6–.[7] In addition, homometallic Ni MCCs are limited to a nuclearity of 12, but this can be increased to 42 by including interstitial carbide atoms.[8] The increased stability of dimetallic and heteronuclear molecular MCCs may result in the appearance of peculiar chemical and physical properties, such as multivalence and paramagnetism.[9] This has been recently exemplified by the Co–Pt dicarbides [Co8Pt4C2(CO)24]n– ([1]n–) (n = 1–4) which display both multivalency (i.e. they undergo several redoxreversible processes) and paramagnetism in the odd-electron monoanion and the even-electron dianion.[10] Herein, we report on the chemical reduction of [1]2–, which results in either [Co10Pt2C2(CO)22]4– ([2]4–) or [Co8Pt4C2(CO)20]4– ([3]4–), depending on the experimental conditions. Both spe- [a] Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy Fax: +39-051-2093690 E-mail: stefano.zacchini@unibo.it [b] Dipartimento di Chimica, Università di Siena, Via De Gasperi 2, 53100 Siena, Italy Eur. J. Inorg. Chem. 2012, 2243–2250 © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2243 [1]n–, [2]n– and [3]n– undergo structural rearrangements resulting, among others, in the formation of the new species [Co10–xPt2+xC2(CO)24]2– ([4]2–) (x = 0–2) structurally related to [1]2–. These dodecanuclear M12C2 dicarbido clusters are not isostructural and differ in the metal composition and/or the number of CO ligands. Nevertheless, they can be readily interconverted even if the interconversion reactions are not straightforward.