Synthesis and characterization of heterometallicbl] clusters

Abstract

Interest towards heterometallic clusters and their reactivity is increasing [1]. Most of these species were obtained via redox condensation or via reactions of carbonylmetalates in polar solvents; some were prepared by pyrolytic reactions in apolar solvents. We now report a synthetic method for neutral mixed clusters, based on the pyrolysis of cyclopentadienyl-nickel derivatives and of iron or ruthenium ▪ carbonyl or alkynecarbonyl dusters, in hydrocarbon solvents. Complexes (cp)NiFe 2(CO) 6C 2R (R = Me [2], Bu t [3]) (I), (cp)NiFe 2(CO) 7C·CH 2R (R = Me [2], Bu t [3]) (II), (cp) 2Ni 2Fe 2(CO) 7 [4] (III), (cp) 2Ni 2Fe 2(CO) 6(C 2Et 2) [4](IV), (cp)NiRu 3(CO) 9C·CH·Bu t [5] (V), and two isomers (cp)NiRu 3(CO) 8(C 6H 9) [6] (VI) were characterized. The nature and yield of products is dependent from clusters stability; iron clusters are usually broken to give complexes containing two iron atoms, whereas from the ruthenium clusters mixed species, still containing three ruthenium atoms, are obtained. The structures of the complexes (I), (III), (IV), (V) and (VI) (one isomer), determined by X-ray diffraction methods, are shown in Fig. 1. In the above reactions, homometallic products are also obtained, as by-products; these are originated by ligand exchange (cyclopentadienyl, alkyne or carbonyl) between the two metals. Comparable behaviour has been observed for the above compounds, in the mass spectrometer; thus comparable pyrolytic processes apparently occur in the solution and vapour phases.