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A reinvestigation of the redox behavior of the [Fe(3)(&mgr;(3)-S)(CO)(9)](2)(-) dianion led to the isolation and characterization of the new [Fe(5)S(2)(CO)(14)](2)(-), as well as the known [Fe(6)S(6)(CO)(12)](2)(-) dianion. As a corollary, new syntheses of the [Fe(3)S(CO)(9)](2)(-) dianion are also reported. The [Fe(5)S(2)(CO)(14)](2)(-) dianion has been obtained by oxidative condensation of [Fe(3)S(CO)(9)](2)(-) induced by tropylium and Ag(I) salts or SCl(2), or more straightforwardly through the reaction of [Fe(4)(CO)(13)](2)(-) with SCl(2). The [Fe(6)S(6)(CO)(12)](2)(-) dianion has been isolated as a byproduct of the synthesis of [Fe(3)S(CO)(9)](2)(-) and [Fe(5)S(2)(CO)(14)](2)(-) or by reaction of [Fe(4)(CO)(13)](2)(-) with elemental sulfur. The structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)] were determined by single-crystal X-ray diffraction analyses. Crystal data: for [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)], monoclinic, space group P2(1)/c (No. 14), a = 24.060(5), b = 14.355(6), c = 23.898(13) Å, beta = 90.42(3) degrees, Z = 4; for [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)], monoclinic, space group C2/c (No. 15), a = 34.424(4), b = 14.081(2), c = 19.674(2) Å, beta = 115.72(1) degrees, Z = 4. The new [Fe(5)S(2)(CO)(14)](2)(-) dianion shows a "bow tie" arrangement of the five metal atoms. The two Fe(3) triangles sharing the central Fe atom are not coplanar and show a dihedral angle of 55.08(3) degrees. Each Fe(3) moiety is capped by a triply bridging sulfide ligand. The 14 carbonyl groups are all terminal; two are bonded to the unique central atom and three to each peripheral iron atom. Protonation of the [Fe(5)S(2)(CO)(14)](2)(-) dianion gives reversibly rise to the corresponding [HFe(5)S(2)(CO)(14)](-) monohydride derivative, which shows an (1)H-NMR signal at delta -21.7 ppm. Its further protonation results in decomposition to mixtures of Fe(2)S(2)(CO)(6) and Fe(3)S(2)(CO)(9), rather than formation of the expected H(2)Fe(5)S(2)(CO)(14) dihydride. Exhaustive reduction of [Fe(5)S(2)(CO)(14)](2)(-) with sodium diphenyl ketyl progressively leads to fragmentation into [Fe(3)S(CO)(9)](2)(-) and [Fe(CO)(4)](2)(-), whereas electrochemical, as well as chemical oxidation with silver or tropylium tetrafluoroborate, in dichloromethane, generates the corresponding [Fe(5)S(2)(CO)(14)](-) radical anion which exhibits an ESR signal at g = 2.067 at 200 K. The electrochemical studies also indicated the existence of a subsequent one-electron anodic oxidation which possesses features of chemical reversibility in dichloromethane but not in acetonitrile solution. A reexamination of the electrochemical behavior of the [Fe(3)S(CO)(9)](2)(-) dianion coupled with ESR monitoring enabled the spectroscopic characterization of the [Fe(3)S(CO)(9)](-) radical monoanion and demonstrated its direct involvement in the generation of the [Fe(5)S(2)(CO)(14)](n)()(-) (n = 0, 1, 2) system.

Transition metal carbonyl clusters of high nuclearity are often closely related to fragments of a metal lattice; more rarely, clusters that can be considered as an extended fragment of the lattice of a binary compound have been stabilized in a ligand shell, although some important examples of this type of cluster are known.". Metal carbonyl clusters that exhibit the above behavior are of interest since they may provide a molecular approach to new materials,l3I and may be used as models for both experimentalL4] and theoretical studies.151Several years ago we reported the synthesis and crystal structure of the nickel carbide cluster 1 and its corresponding hexaanion 2;(,] the Ni,,C, inner core of 1 is closely related to the [HNi38C,(Co)4215-1 M,,C, truncated-octahedral fragment that is present in the M,,C, lattice, for example, in CT,,C,.~'~ The method for preparing these clusters was improved recently, and thus it has now been possible to study their reactivity. As part of these reactivity studies we report here on the synthesis and crystal structure of the new [Ni,,C,,,]6 hexaanion 3, which consists of the above-mentioned M,,C, fragment stabilized in a shell of 36 edge-bridging carbonyl groups. and a change in the pattern of the carbonyl absorption bands of 2 (1992s, 1817s, 1862s cm-') was observed when the reaction was monitored by IR spectroscopy.@' As the reaction proceeds, the absorption band attributed to the terminal carbonyl groups (1992 cm-I ) becomes progressively less intense, and the two bands attributed to the edge-bridging carbonyl ligands collapse into a single absorption band that is shifted to a slightly higher wavenumber. The intermediate IR patterns suggest the possible formation of [Ni,,-xC,(CO),,_,]6-(x = 1-5) species by stepwise elimination of Ni(C0) moieties. All [Ni38-xC6(CO)42 Owing to their very low solubility, the salts of 3 separate out, together with some insoluble inorganic material, from the reaction solution containing 5."01 The quaternary ammonium and phosphonium salts have been purified by extraction in MeCN and crystallized by layering the extracts with diisopropyl ether.The unit cell of the [PPh,Me], salt of 3 contains one cluster anion located on a crystallographic inversion center, six cations, and four acetonitrile molecules.["] The structure of 3, which shows an overall idealized 0, symmetry, is shown in Figure 1. The truncated octahedral Ni,,C, framework of 3 is identical to the corresponding fragment in 1, and reveals very close interatomic separations. The structure contains an inner, empty Ni, cube (av Ni-Ni = 2.397 A) whose six faces are capped by carbon atoms, which describe a C, octahedron without bonding interactions between the C atoms. This inner Ni,C, moiety is surrounded by a truncated-octahedral Ni,, shell (av NiNi = 2.461 A). The Ni atoms of the Ni,, shell are arranged in such a way that they generate six square-antiprismatic cavities, in which the six carbide-C atoms (av Ni-C = 2.062 A) are located. Each Ni atom of the inner cube lies approximately 0.93 A bel...

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