Mixed-metal carbonyls preparation

The mercury compounds HgFe(CO)4 and Fe(CO)4(HgX)2 (X = C1, Br, I), which were the first representatives of non-ionic metal derivatives of iron carbonyl hydrides, were discovered by Hock and Stuhlmann (V, 36). During investigations into the preparation of cobalt carbonyls from cobalt halides under CO pressure, in the presence of another metal as a halogen acceptor, we discovered the mixed metal carbonyls M[Co(CO)4]2 (M = Zn, Cd, Hg, Sn) and M[Co(CO)4]3 (M = In, Tl) (44), e.g.,... 

As mentioned above, the addition of promoters, and even the formation of bimetallic particles, can provide carbon-supported iron catalysts with better performances in CO hydrogenation. The method of preparation of these systems is going to determine the final effect, always taking advantage of the relative inertness of the carbon surface. The interaction between the different components of the active phase can be maximized by using mixed-metal carbonyl complexes. Furthermore, use of these precursors allows for the preparation of catalysts with... 

The main current interest in the metals of this group (as far as carbonyls are concerned) lies in the preparation of mixed metal carbonyls (see below). The number of papers... 

Catalytic and photochemical processes using mixed metal carbonyls are also represented. Tin-cobalt carbonyl compounds have been used as catalysts for ring-opening of oxiranes by secondary and tertiary alcohols 121 and the photochemical reactions of Pt2M4(CO)jg (M=Os, Ru) with cycloocta-1,5-diene under UV irradiation 122,123,124 jjgve been reported. A new rhenium-cobalt complex has been characterised 126 and Pt(cod)2 has been used to prepare new complexes via its reaction with 0 3(CO) jQ(FlCMe)2 26. 

In addition, to facilitating the preparation of highly dispersed iron catalysts, the use of iron carbonyls and carbon supports facilitates the preparation of promoted catalysts to increase the selectivity to olefines. Thus, the use of mixed-metal carbonyl clusters as metal precursors allows the preparation of a variety of stoichiometric metal compositions, something difficult to reach by co-impregnation techniques. Furthermore, the mixed-metal carbonyl cluster should be activated by heating just to that minimum temperature which would decompose the cluster to yield reduced metal and CO, the temperature being <475 K. Hence, it is possible to obtain reduced metals under much less severe conditions than those used for conventional metal salt precursors. 

Preparation of Mixed-Metal Carbonyls by Metathesis Reaction... 

The mixed-metal tetranuclear derivatives that have been prepared are H2Re2Ru2(CO)i6, CReRu3(CO)16] , HMnOs3(CO)16, and HReOs3(CO)18 (238). All the complexes result from the reaction of the carbonyl, M3(CO)i2, with the related anion, [Mn(CO)5]- or [Re(CO)s]. The ruthenium anion [ReRu3(CO)16] was isolated as its tetramethylammo-nium salt. The infrared spectrum was complex, but consistent with... 

Fe(CO)s], [Fe2(CO)g], [Co2(CO)8] and [Os3(CO)i2]) have been reacted with dicyanobenzene to form intrazeolite [M(Pc)] complexes [140]. Another class of materials prepared by the intrazeolite template synthesis method has been mixed ligand metal carbonyls and metal carbonyl clusters, frequently by reductive car-bonylation of metal ions in zeolite cages [175]. However, because these are frequently decomposed in situ to form, for example, nanoparticles, they are outside the scope of this chapter, and will be considered here only when they are used as precursors for metal complexes. 

This derivative of the [OMo6Ojg]z structure (Section 4.6.8.1), by addition of an ML3 cap on a triangular (ji-0)3 face of the (fi-0)i2 cuboctahedron, is proposed269 for [(C0)3ReNb2W4019]3 (prepared by [Nb2W4Oi9]4 + [(CO)3Re(MeCN)3]+ in MeCN), which belongs to a class of mixed mode clusters amalgamating polyoxometallates and metal carbonyls. 

F. Mixed Cyanocarbonyl Metalates Prepared from Metal Carbonyl Derivatives and NaN(SiMes)2. 38... 

The reaction of [Fe(CO)J2- and [CoICOJJ- with metal carbonyl trimers has also been shown to be useful for the preparation of mixed-metal clusters, Eqs. (33) (78) and (34) (147). 

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