Magnetic Behavior of Odd- and Even-Electron Metal Carbonyl Clusters: The Case Study of [Co₈Pt₄C₂(CO)₂₄]ⁿ⁻(n= 1, 2) Carbide Cluster

Abstract

The reaction of [Co(6)C(CO)(15)](2-) with 2 equiv of PtCl(2)(Et(2)S)(2) affords the new heterobimetallic [Co(8)Pt(4)C(2)(CO)(24)](2-), [1](2-), carbonyl cluster. [1](2-) undergoes reversible chemical and electrochemical oxidation and reduction processes disclosing a complete series of [1](n-) (n = 1-4) clusters. The mono- and dianion of [1](n-) have been isolated as their tetra-substituted ammonium salts and fully characterized by means of IR, (13)C NMR, ESI-MS, and X-ray crystallography. Variable-temperature (VT) solid-state EPR studies on pure crystalline samples indicate that both [1](2-) and [1](-*) are paramagnetic, due to a doublet state of the latter and a triplet state of [1](2-). This conclusion is supported by SQUID measurements on the same crystalline sample of [1](2-). The present study indisputably demonstrates that even-electron transition metal carbonyl clusters (TMCC) can be magnetic.

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

“…Both, [1] 2and [1]have been isolated and structurally characterised. [10] In an attempt to isolate [1] [1] n-(n = 3-4), and the resulting suspension was divided into two portions. One portion was treated according to procedure (A) and the second according to procedure (B) resulting in the isolation of [2] 4 ] or dilute acids) and reduced (with Na/naphthalene) yielding [3] n-(n = 1-6) (Scheme 3).…”

“…Alternatively, the metal polyhedron can be viewed as composed of two trigonal-prismatic Co 6 C units sharing a vertical edge plus two extra Pt atoms capping simultaneously the facing square faces of the prisms. [10] Thus, it is composed of three face-sharing octahedra, the external ones being centred by two C atoms. The structure is completed by 12 terminal CO ligands (one per metal atom) and 10 edge-bridging carbonyl groups (four on each square layer and two spanning opposite Co-Pt bonds in the central rhomb).…”

“…However, as shown in Figure 7, deconvolution of the cyclic voltammogram as well as differential pulse voltammetry suggest that it apparently un- Despite the multiple redox processes exhibited by [2] 4and [3] 4-, no redox congeners have been isolated because of the cluster reorganisations (or degradations) accompanying the electron-transfer processes. [10] Conversely, the reduced species [ Moreover, a second irreversible oxidation process was detected.…”

“…[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. [10] Herein, we report on the chemical reduction of [1] 2-, which results in 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. [9] This has been recently exemplified by the Co-Pt dicarbides [Co 8 Pt 4 C 2 (CO) 24 ] n-([1] n-) (n = 1-4) which display both multivalency (i.e.…”

Electron Reservoir Activity of High-Nuclearity Transition Metal Carbonyl Clusters

“…As expected on the basis of the electrochemical reversibility, the variations in metal-metal bonds are rather limited, Table 7. As a matter of fact the monoanion [Co 8 Pt 4 C 2 (CO) 24 ] − has been crystallographically characterized [25] and a few significant structural parameters are reported in Table 8. Since the distances Ag-Ag tend to decrease and the Ag-Fe tend to increase with the addition of electrons, it is evident that the LUMOs of the cluster are bonding with respect to the Ag-cuboctahedron and antibonding with respect to the Fecapping subunits.…”