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The two clusters [HFe5NiN(CO)14]2- (1) and [HFe4Ni2N(CO)13]2- (2) were obtained by reaction of [Fe4N(CO)12]- and [Ni6(CO)12]2- in refluxing MeCN and EtCN, respectively, along with other Fe-Ni mixed metal clusters. Their solid state structures were determined on the [PPh4]+ salts, and both have an octahedral metal cage, containing an interstitial nitrogen atom. The two Ni atoms in 2 are cis, with a Ni-Ni separation of 2.724(1) Å. The two anions have different stereochemistry of the carbonyl ligands: in 1, five CO's are semi-bridging, and the remaining nine are terminal; in 2 there are three asymmetric bridging and ten terminal ligands (two for each iron and one for each nickel). The hydride ligands were located in the final difference maps, both bridging a Ni-Fe edge of the clusters but, thanks to the better quality of the diffraction data, the metal-hydrogen distances were refined only in 2. In this cluster, the Fe-H and Ni-H bond lengths are 1.77(2) and 1.79(2) Å, respectively. © 2006 Elsevier B.V. All rights reserved.

The reaction between norbornene (C7H10) and Ir-6(CO)(16) in refluxing toluene yields the substituted cluster [Ir-6(CO)(14)(C7H8)]. In the solid state, the six iridium atoms define an octahedral metal cage, and one face is capped by the C7H8 ligand, coordinated through a 1,2-vinylidene unit. The loss of two hydrogen atoms from the olefin is, presumably, the result of a double oxidative addition of its C-H bonds, followed by elimination of a hydrogen molecule from the cluster. The bonding parameters of the organic fragment, as well as the architecture of the carbonyl ligands, closely match those found in the alkyne-substituted [Ir-6(CO)(14)(PhCCPh)] complex. The cluster [Ir-6(CO)(14)(C7H8)] was characterized through H-1-, C-13- and bidimensional COSY NMR.

The three clusters [Fe6Ni6N2 (CO)24]n- (n = 2-4) have been isolated, and their solid-state structures determined. The clusters are composed by three face-sharing octahedra, with the external ones filled by two interstitial nitride. The addition of electrons brings about swelling of the central, empty octahedron. Cyclic voltammetry shows that redox conversions of the three clusters are totally reversible. Extended Hückel and density functional calculations have been performed, to explain this behavior. © 2005 Académie des sciences. Published by Elsevier SAS. All rights reserved.

The cluster [FeNi5(CO)(13)] (2-) (1) was obtained by reaction of Fe(CO)(5) and [Ni-6(CO)(12)](2-) (2), in acetonitrile at room temperature. Its solid state structure was determined on the [NEt4]() salt, and consists of a trigonally distorted octahedron, with six edge-bridging ligands. This assembly strictly recalls the architecture of the prototypical [Ni-6(CO)(12)](2-) anion, by formal replacement of one Ni(CO) unit with the Fe(CO)(2) fragment. However, the requirements of the additional ligand have sterical consequences on the other carbonyl groups, which can not be coplanar as in the all-nickel cluster. [FeNi5(CO)(13)](2-) reacts readily with acids, to yield the already known [HFe3Ni(CO)(12)](-) (3), and with CO, being stepwise fragmented to species of lower nuclearity, ending with [Fe3Ni(CO)(12)](2-) (4) or [Fe-2(CO)(8)](2-). The solid state structure of the tetranuclear [Fe3Ni(CO)(12)](2-) was also determined, and is reported here. (C) 2002 Elsevier Science B.V. All rights reserved.

Reaction of [Co3(CO)9CCl] with [Ni6(CO)12]2- results in a complicated mixture of mixed Co-Ni carbide carbonyl clusters, among which the [Co3Ni9C(CO)21]3- trianion has been isolated in a pure crystalline state and fully characterized by X-ray crystallography. The metal framework of this compound is unprecedented in cluster geometries and may be described as a square antiprism of metal atoms tetra-capped on two alternate pairs of adjacent triangular faces. Despite the presence of a caged carbon atom in the square-antiprismatic cavity, the compound is readily degraded by carbon monoxide (25 "C, 1 atm) mainly to a mixture of [Co(CO)4]- and [Ni(CO)4]. Corresponding degradation of the cluster under a mixture of carbon monoxide and hydrogen yields, in addition, trace amounts of organics, mainly C1 and C2 hydrocarbons, probably derived from the carbide atom.

The synthesis, chemical behavior and single crystal X ray structure of two new CoNi bimetallic carbide clusters, namely [Co 2 Ni 10 (CO) 20 C] 2− and [Co 3 Ni 9 (CO) 20 C] 2− , are reported. The first complex was isolated in ca. 30% yield among the products of the reaction of Co 3 (CO) 9 CCl with [Ni 6 (CO) 12 ] 2− , while the second was obtained quantitatively by reaction with protonic acids of the previously reported [Co 3 Ni 9 (CO) 20 C] 3− . The two compounds are isostructural and show a metal frame which can be regarded as derived by distortion of a tetra-capped triangulated dodecahedron of D 2 d symmetry; the statistical (Co and Ni atoms being undistinguishable) idealized symmetry of the metal frame is only D 2 owing to progressive deformations toward a tetra-capped tetragonal antiprismatic geometry, which are probably related to the steric requirements of the interstitial carbide atom.

The dianion [FeIr4(CO)15]2– can be obtained by reduction of an equimolar mixture of [Fe(CO)5] and [Ir4(CO)12] in alcoholic NaOH and under 1 atm of carbon monoxide. The salt [N(PPh3)2]2[FeIr4(CO)15](1) crystallizes in the triclinic space group P with unit-cell dimensions a= 11.399(3), b= 14.032(3), c= 29.163(4)A, α= 86.18(2), β= 84.52(2), γ= 80.14(2)°, and Z= 2. Its metal framework consists of a trigonal bipyramid with the equatorial triangle formed by iridium atoms. The mean values of the Fe–Ir, Ireq–Ireq′ and Irap–Ireq distances are 2.943, 2.708, 2.991 A, respectively. The monoanion [Fe2Ir3(CO)14]– was obtained from [Fe(CO)4]2– and [Ir(CO)2Cl2]–. The salt [PPh4][Fe2Ir3(CO)14](2) crystallizes in the orthorthombic space group P212121 with unit-cell dimensions a= 12.461(5), b= 14.306(5), c= 23.504(6)A, and Z= 4. Its metallic framework is comprised of an iridium triangle capped on opposite side by two iron atoms. The mean values of the Fe–Ir and Ir–Ir distances are 2.648 and 2.708 A, respectively. In the derivative (1) the trigonal bipyramid is considerably elongated in the direction of the apical atoms, When compared with that in (2). This elongation is consistent with the increased number of cluster valence electrons: 76 in (1) and 72 in (2).

A new approach to the synthesis in good yields of known cobalt and iron carbidecarbonyl clusters by CO cleavage in mild conditions is reported. Cleavage of CO results from attaching an acetyl or benzoyl carbocation to the oxygen atom, and by transfer of electrons from an external source. This synthetic approach to carbide molecular clusters may be of some significance with respect to the formation of carbide atoms on to metal crystallites. Attempts to synthesize nickel carbide clusters with the same approach have only been partly successful. The new [Ni9C(CO)17]2~ and [Ni8C(CO)13]2~ have been obtained more conveniently from the reaction of [Ni6(CO)12]2- with CC14. The related reaction of [Ni6(CO)12]2- with Co3(CO)9CCl results in the formation of the mixed-metal carbide cluster [Co3Ni9C(CO)20]3_. This compound is degraded under a carbon monoxide and hydrogen mixture (25 °C, 1 atm) to Ni(CO)4, [Co(CO)4]~ and ethane. Intermediate formation of [Co3Ni7(C-C) (CO)15]3-, in which the two carbide atoms show an interatomic separation of 1.43 A, or of a related species, would provide a possible pathway for C-C bond formation.

The synthesis and properties of the new dicarbidocarbonyl bimetallic clusters [Co3Ni7(CO)16C2]2− (I), [Co3Ni7(CO)16C2]3− (II), and [Co3Ni7(CO)15C2]3− (III), are described. Compound I, which is paramagnetic, has been synthesized in high yields by redox-condensation of Co3(CO)9CCl with [Ni9(CO)17C]2−, whereas the diamagnetic trianions II and III have been respectively obtained by reduction of I, with sodium metal in THF and sodium hydroxide in methanol. The anion I has been isolated in a crystalline state in association with several tetrasubstituted ammonium or phosphonium cations, which are characterized by elemental analysis and by a single-crystal X-ray diffraction study, of the tetraphenylphosphonium salt. The anion I has a metal frame based on a 3,4,3-C2h stack of metal atoms, which may be regarded as derived by condensation of two either octahedral or trigonal-prismatic moieties. The resulting deca-vertices metal polyhedron encapsulates a C2 fragment showing a short CC interatomic separation of 1.48 A. The three cobalt atoms cannot be distinguished from the remaining seven nickel atoms and are probably randomly distributed over the ten vertices. The M-M distances are scattered over the range 2.34–2.80 A, and each carbide carbon is encapsulated in a seven-vertices cage which may be described as a distorted capped trigonal prism. The carbonyl stereochemistry comprises six carbonyl groups terminally bonded to the atoms of the top and bottom triangular layers, and ten edge-bridging CO which span the ten inter-layer edges. The structure of this decanuclear dicarbide cluster is compared with those reported for related species and a rationalization is offered for the variations of the metal geometry and the CC interatomic separation.

In the title compound two C‐atoms are located in the cavity of a cluster. The CċC distance in very short—only 1.49 Å (for comparison: CC single bond 1.54 Å)—but, as deduced from a consideration of the number of cluster valence electrons, a delocalized CC interaction is more probable than a localized one. (Figure Presented.) Copyright © 1984 by Verlag Chemie, GmbH, Germany

The cluster [Fe5MnN(CO)16]2 (1) was synthesized from [Fe6N(CO)15]3- and Mn2(CO)10, in refluxing EtCN, or [Fe4N(CO)12]- and [FeMn(CO)9] -. Its solid state structure was determined on the [Me3NCH2Ph] + salt, and consists of an octahedral metal cage, enclosing a six-coordinated nitrido ligand. The position of the manganese atom in the solid state could be established, despite some crystallographic disorder, by considering the local stereochemistry of the ligands. The cluster [Fe6N(CO)14NO]2- (2) was obtained in moderate yields by the reaction of [Fe4N(CO12] with Mo(CO)3(EtCN)3. The nitrosyl is formed by oxidation of the starting nitride, and the source of the oxygen is presumably a carbonyl, whose splitting is mediated by the molybdenum complex. This process is the first example of an oxidation of a nitride in a carbonyl cluster. The solid state structure of the iron cluster is also octahedral, and the linear nitrosyl ligand was unambiguously located from the short Fe–N bond distance, and from dishomogeneous distribution of ligands. Cyclic voltammetric studies have shown that electron transfer processes are followed by chemical reactions thus testifying that no stable redox congeners exist for these two nitride clusters.

The cluster [Ir 4 (CO) 11 (CPhCHPh)] − was obtained by reaction of [HIr 4 (CO) 11 ] − and diphenylacetylene by refluxing in tetrahydrofuran (THF), with yields approaching 80%. The solid state structure was determined on the [NEt 4 ] + salt; the cluster possesses a tetrahedral metallic framework, with three edge bridging carbonyls. The vinyl fragment, having two phenyl rings in cis , is bound in axial position and donates only one electron to the cluster, since the CC double bond (1.34 A) does not interact with any iridium atom. The 13 C-NMR of the cluster, recorded at −90°C, allows full assignment of the signals. The cluster [Ir 6 (CO) 14 (COOMe) 2 ] 2− was obtained by nucleophilic attack of MeONa on [Ir 6 (CO) 16 ], in anhydrous methanol at room temperature. The solid state structure was determined on its [N(PPh 3 ) 2 ] + salt. Two methoxycarbonyl fragments are on adjacent metal vertices of the octahedral framework.