Carbido carbonyl clusters

The formation of carbido-carbonyl cluster compounds with ruthenium and osmium appears to be common in pyrolysis reactions the basic reaction may be viewed as the transformation of the coordinated carbon monoxide to carbide and carbon dioxide. Small variations in... 

Only two kinds of reagent have been extensively used for this type of reaction so far. These are the anionic carbido carbonyl clusters of iron and... 

Paolo Chini began his work in the late 1950s with the characterization of cobalt carbonyl species involved in the hydroformylation of olefins with cobalt catalysts, and in the course of these studies developed improved synthetic methods for the known cobalt carbonyls Co2(CO)8 and Co4(CO)12 [132]. His next steps were the preparation of the heterometallic hydrido complex HFe-Co3(CO)i2 (isoelectronic to Co4(CO)12) and the corresponding anion [FeCo3(CO)12], both a novelty at that time, and of the new hexanuclear cobalt clusters [Co6(CO)15]2, [Co6(CO)14]4, and Co6(CO)16 [133-139]. This work was followed by the synthesis of carbido carbonyl cluster anions [Co6(CO)i4C], [Co6(CO)15C]2 and [Co8(CO)i8C]2, containing an interstitial... 

This anion provides both the first example of a trigonal prismatic hexanuclear cluster and one of the more easily prepared carbido-carbonyl cluster compounds. 

The compound K2 [Rh6(CO)15C] is a yellow powder. It is sensitive to air both in the solid state and in solution and is quite soluble in water, methanol, ethanol, acetone, THF, and acetonitrile. The salts of other cations can be obtained by metathesis, in water for the cesium salt and in methanol for the larger tetra-alkylammonium or phosphonium cations. The tetraethylammonium salt is sparingly soluble in THF, whereas the benzyltrimethylammonium and bis-(triphenylphosphine)imminium salts are soluble. All of these salts are soluble in acetone and acetonitrile. The yellow solution of the potassium salt in THF shows characteristic IR bands at 2040 (vw), 1990 (vs), 1885 (vw), 1845 (s), 1830 (sh, m) 1815 (sh, br) and 1775 (vw, br) cm-1. The IR spectral band shapes depend on solvents and cations. The oxidation of K2 [Rh6(CO)i5C] with iron-(III) ammonium sulfate in water under carbon monoxide leads to the octa-nuclear carbido carbonyl cluster Rhg(CO)i9C,6 whereas under nitrogen RhntCO sQ7 or [H30] [Rhls(CO)28C2]8 is obtained. 

Figure 7-12 The structures of some representative carbido carbonyl cluster species, (a) Fe5C(CO)15, (b) Ru C(CO)17, (c) [Osi0C(CO)24]2-, and (d) Fe4C(CO)i3.

CO have been activated by reacting osmium carbido-carbonyl clusters with alcohols to form coordinated CO2R groups under mild conditions no evidence of surface effects was established. A comparable reaction is methoxide attack on... 

OssC(CO) (C02R)X] (X = H or I) has been determined, and the metal core shown to exhibit the expected bridged-butterfly geometry. Another preliminary report on nucleophilic attack at a coordinated CO of a carbido carbonyl cluster compound has also appeared. The heterometallic carbido cluster anion [Co6Ni2C2 (C0)i6 ] results from the reaction of [003(00)9(001)] with [Nig (C0)i2 ] and contains two C atoms located in a cavity in the cluster and separated by only... 

The reaction with [Mn(CO)5]2 or [Co(CO)4]2 also led to mixed-metal clusters.962,963 Osmium-palladium mixed-metal carbonyl clusters were made using the unsaturated cluster [Os3(CO)io(/r-H)2] and the carbido cluster [Os5(/U5-C)(CO)15].964 970 Treatment of [Os3(CO)10Gu-H)2] with [Pd2(/u-dppm)2Cl2] afforded the novel high-nuclearity osmium-palladium mixed-metal carbonyl clusters [Os5Pd6(CO)13( -CO)5(/u-H)2(/u-dppm)2], [Os5Pd6(CO)13(//-CO)6(/u-dppm)2], and... 

F.G.A. Stone Yes, I would expect cleavage of the W=C bond in [(n-C5H5)(0C)2W=CR] to occur in certain reactions. Indeed, we believe we have observed C=W bond cleavage in a reaction of the tungsten compound with a carbido(carbonyl)iron cluster. Interestingly, [(n-C5H5)(0C)2W=CR] reacts with sulphur to yield [(n-C5H5)(0C) W S CR S] (I. Moore, Bristol University). 

Interest in the high nuclearity carbonyl clusters of ruthenium has centered around the hexanuclear carbido-cluster Ru6C(CO)17 and its derivatives, Ru5C(CO)15 and, more recently, [Ru C CO) ]2-.1 The chemistry of both Ru6C(CO)17 and Ru5C(CO)15 has been investigated in some detail. Their syntheses are described below. 

M. P. Cifuentes, M. G. Humphrey, J. E. McGrady, P. J. Smith, R. Stranger, K. S. Murray, and B. Moubaraki, High Nuclearity Ruthenium Carbonyl Cluster Chemistry. 5. Local Density Functional, Electronic Spectroscopy, Magnetic Susceptibility, and Electron Paramagnetic Resonance Studies on (Carbido)decaruthenium Carbonil Clusters, J. Am. Chem. Soc. 119,2647-2655 1997. 

Carbide, iron complex, 26 246 Carbido carbonyl ruthenium clusters. 

Table 2. Orientation of the carbonyl ligands at the wingtip (d) and at the hinge (x) of the carbido butterfly clusters of type 12. X represents a group linked to the carbide atom, Y is a group bound to the lower Fe- Fe hinge.

The chemistry of metal carbonyl clusters containing exposed or semi-exposed main-group elements has received attention because of the belief that such molecular clusters might serve as models for the chemisorption and subsequent reactivity of the corresponding species on a metal surfaceJ In particular, the M4 butterfly clusters containing / 4-carbido and -nitrido ligands have played a pivotal role in the development of the area, because of their obvious similarities to stepped-sites on metal surfaces. 

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