Heterometallic nitrido-carbonyl clusters synthesis and characterization of [Fe5MN(CO)(14)(C5H5)](2-) [Fe3M3N(CO)(18)](3-) (M = Mo, W) and [HFe5MoN(CO)(16)](2-) and solid-state structures of [Fe5MoN(CO)(14)(C5H5)](2-), [Fe5WN(CO)(14)(C5H5)](2-), and [Fe3Mo3N(CO)(18)](3-)

The anionic clusters [Fe5MN(CO)14Cp]2- [M = Mo (1) or W (2)] were synthesized from [Fe4N(CO)12]- and [MCp(CO)3]- in refluxing acetonitrile. The clusters [Fe3M3N(CO)18]3- [M = Mo (3) orW(4)] were prepared by reaction of [Fe4N(CO)12]- with [M2(CO)10]2- under the same conditions. The molybdenum- containing anions 1 and 3 are obtained in higher yields than 2 and 4. The reaction of the tetranuclear iron cluster with [Mo(ç6-Me3C6H3)(CO)3] affords a mixture of [Fe3Mo3N(CO)18]3- and [HFe5MoN(CO)16]2- (5). The solid state structures of the clusters 1, 2 and 3 have been determined; they consist of six metal atoms, arranged in octahedral metal cages encapsulating a ì6-N ligand. The cyclo- Introduction The interest in heterometallic clusters is still growing, and several examples of their application in catalysis can be found in the literature.[1] In homogeneous catalysis, mixed metal species are preferred, due to the presence of polar metal2metal bonds which can tune electron density at the metal centres, thus modifying the reactivity of the coordinated ligands.[2] In the field of heterogeneous catalysis, mixed-metal species can be exploited for the formation of bimetallic particles which are extraordinarily uniform in their morphology and composition.[3] In this context, the stability of the cage due to the interstitial atoms can avoid [a] Dipartimento di Scienze dell’ Ambiente e del Territorio, Universita` di Milano-Bicocca Piazza della Scienza 1, 20126 Milano, Italy rpergola@mailserver.unimi.it Fax: (internat.) 1 39-02/236-2748 [b] Dipartimento di Chimica Inorganica, Metallorganica ed Analitica and Centro del CNR Universita` di Milano, via G. Venezian 21, 20133 Milano, Italy [c] Dipartimento di Biologia Strutturale e Funzionale, Universita` degli studi dell’Insubria, via J. H. Dunant 3, 21100 Varese, Italy [d] Dipartimento di Chimica Strutturale e Stereochimica Inorganica and Centro del CNR 2 Universita` di Milano via G. Venezian 21, 20133 Milano, Italy E-mail: m.manassero@csmtbo.mi.cnr.it Eur. J. Inorg. Chem. 2000, 175921765 ÓWILEY-VCH Verlag GmbH, D-69451Weinheim, 2000 143421948/00/080821759 $ 17.501.50/0 1759 pentadienyl ligand is bound to Mo in 1 and to W in 2; these anions have three edge-bridging carbonyl groups and eleven terminal carbonyl groups. The cluster 3 possesses three molybdenum atoms in a fac arrangement, and the carbonyl ligands are all terminal, or asymmetrically bridging. Inspection of the interatomic distances suggests that molybdenum interacts preferentially with the carbonyl and the nitrido ligands, whereas the iron atoms bind strongly with the other metal centres. The solid state structure of 5 could not be fully resolved owing to crystal disorder. Analytical and spectroscopic data (infrared and 1H NMR) are all consistent with the proposed formula.