BS8 I TSThe compounds [ ReCr(rCC,H,Me-4) (CO),] and [ Fe,( CO),] in diethyl ether at room temperature afford the trimetal complex [CrReFe(p3-CC,H,Me-4) (p-CO) (CO),,]. An X-ray diffraction study established that there are two independent molecules in the asymmetric unit and that the molecular structure consists of a p,-CCrReFe core with the chromium and the rhenium atoms ligated by four carbonyl groups and the iron atom by three such groups. A carbonyl ligand bridges the Cr-Re vector, however, the chromium and rhenium sites are disordered (60 : 40) and since the molecules have pseudo-mirror planes relating the metal tetracarbonyl fragments the bridging CO group may not be symmetrically disposed. Reactions between the compounds [ ReM (rCC,H,Me-4) (CO),] ( M = Mo or W) and [Fe,(CO),] afford the related cluster compounds [MReFe(p3-CC,H,Me-4)(p-CO) (CO),,], but these species were shown to be formed via the intermediacy of the complexes [MReFe(p-CC,H,Me-4) (CO),,]. The compounds [CoW(rCC6H,Me-4)(CO),] and [Fe,(CO),] react to give the cluster complex [CoFe,(p,-CC,H,Me-4) (p-CO) (CO),], and reactions of the latter with PPh, and with Ph,PCH,PPh, are described. Spectroscopic data for the new complexes are reported and discussed. Analysis of the l3C-{lH) n.m.r. data for [CoFe,(p3-CC,H,Me-4) (p-CO) (CO),] has shown that the aromatic ring of the tolylmethylidyne group is locked into a fixed position at -80 "C. However, in the closely related cluster [Co3(p,-CC,H,Me-4)(CO),] the group is free to rotate about the p3-C-C1 axis at this temperature. These results have been interpreted in the light of extended Huckel molecular orbital calculations on the bonding of these molecules.We are currently investigating reactions of the compounds [ReM(=CC4H,Me-4)(CO),] (1, M = Cr, Mo, or W) with lowvalent metal species in the expectation that these dimetal complexes will be useful precursors to metal clusters. In the previous paper, we showed that platinum(o) fragments will combine with the carbon-metal triple bonds present in the compounds (1) to give new tri-and penta-nuclear metal clusters.Earlier we reported ' reactions with [co,(co),] which afford the cluster complexes [MReCo,(p3-CC,H,Me-4)(CO), J.Herein we describe reactions of [Fe,(CO),] with the dimetal compounds (1) which yield 'mixed-metal' clusters containing iron. We also report some preliminary work using the compound [CoW(~C4H,Me-4)(CO),] (2) as a reagent for metal cluster synthesis.
Results and DiscussionTreatment of the compounds (lb) and (lc) with one equivalent of [Fe,(CO),], in diethyl ether at room temperature, afforded the orange crystalline complexes [MReFe(p-CC,H,Me-4)-(CO),,] (3b, M = Mo; 3c, M = W). However, the corresponding reaction with (la) gave only a red-brown complex 2,3-pCarbonyl-1,
