Metal carbonyls homonuclear

A few of the heteronuclear metal carbonyls that have been reported are presented in Table 1. In most cases the stmctures of the heteronuclear species are similar to thek homonuclear analogues (11) is a notable exception (39) [Hg2Co2(CO)2]-ll-Hg2[Hg2Co2(CO)2] [100851-89-6]. 

Whereas a large number of metal-sulfur clusters are present in nature, carbonyl clusters are exclusively products of chemical synthesis. They have been widely used in industrial catalytic processes17 and some of these processes are triggered by the redox aptitude of these species.lc g As for the metal-sulfur clusters, we will briefly discuss their structures and their propensity to donate/accept electrons in order of increasing nuclearity. We will consider only homonuclear and homoleptic metal-carbonyl derivatives. However, it is noted that heteronuclear derivatives are gaining considerable interest due to the synergistic effect of metal-metal bonds possessing a polar character.lc,ld... 

Having reviewed the electrochemistry of homo- [10] and heterometal-sulfur clusters [11], we have directed our attention to metal-carbonyl clusters. The stereochemical effects associated with the redox behaviour of homonuclear complexes have been recently reported [13]. In this review, those of heteronu-clear compounds are discussed. Cluster compounds are classified according to their nuclearity as well as their geometrical assembly. Main-group elements at the borderline between metals and non-metals are treated as metallic elements. Occasionally, polynuclear compounds having no metal-metal bonds (and, as such, are not classifiable as clusters) are also included. 

Table 2.18. Some Stable Homonuclear and Heteronuclear Transition Metal Carbonyls...

As befits current interest, the largest number of reviews centre on metal carbonyl cluster compounds. General topics covered included electron transfer reactions, ligand and cluster transformations, and the chemistry of metal clusters containing nitrosyl and nitrido ligands.More specific topics reviewed include sulphi do-osmium carbonyl cluster compounds,and homonuclear platinum clusters.The preparations of [Nb(C0)6] [M2(CO)io(m-H)]" (M = Cr or W), Mn2(C0)aX2 and Re C0)sX (X = Cl, Br or I) are described in Volume 23 of Inorganic Syntheses. ... 

In Table II are listed the neutral homonuclear carbonyls of the Group VIII metals that have been identified to date. Although palladium and platinum do not have any stable neutral carbonyls, a large... 

Table 8.1 compiles the most common stable homonuclear neutral binary carbonyls. They can be prepared by direct carbonylation of pure metals or made from available metallic precursors by reductive carbonylation. However, most of them are commercially available. Moreover, heteronuclear carbonyl compounds are known, and they are usually prepared by reaction between homonuclear binary carbonyls or carbonyl-derivative complexes. 

Rh, are the base of active catalysts for CO hydrogenation and the hydroformylation of olefins. The presence of several promoters modifies their catalytic behavior and synergic effects on the base-metal have been observed Table 8.5 illustrates several examples in which homonuclear or heteronuclear carbonyl compounds have been used in the preparation of Co- or Co-Rh-based catalysts for the CO hydrogenation and/or hydroformylation reactions. 

In this more carbonylated species the hexametal assembly assumes an octahedral architecture, with four carbonyl groups p3-face bridging and twelve terminal. This geometry is quite reminiscent of that exhibited by the red isomer of the isoelectronic homonuclear Ir6(CO)16 [164]. Although the expected spreading of the metal-metal distances, their averaged value still remains 2.77 A. 

Polynuclear Carbonyl Derivatives.-Variable temperature MAS n.m.r. methods have been used to probe the exchange processes occurring in solid homonuclear carbonyls containing 3 and 4 metal atoms.A quantitative investigation of the chemistry resulting from both continuous- and flash-photolysis of Ru3(C0)i2 has been carried out, and a new polymeric ruthenium carbonyl, Ru(C0)it n prepared from this precursor. The steric and electronic effects in associative substitution reactions of Iri (C0)i2 have also been examined. The combination of two OS3 units to yield an improved route to Ose raft-like clusters has been achieved, and a comprehensive analysis published on the different Mg cores of stacked Mg triangles in the [Mg C0)i8] "... 

---