Polynuclear carbonyl anions

Ni(CO)4] is readily oxidized by air and can be reduced by alkali metals in liquid ammonia or thf to yield a series of polynuclear carbonylate anion... 

Fig. 12. Infrared spectra of rhodium and platinum polynuclear carbonyl anions in the carbonyl stretching region (tetrasubstituted ammonium or phosphonium salts in THF). MA/NC, ratio of number of metal atoms to the number of negative charges.

P. Chini, G. Longoni, V. G. Albano, Adv. Organomet. Chem., 14, 285 (1976) although confined to clusters containing five or more metal atoms, a good general discussion of synthetic methods for polynuclear carbonyl anions. 

The surface reaction of impregnated mixed metal cluster complexes may be analogous to that of homometallic clusters on hydrated and dehydrated metal oxides as described in Sections III and IV. Bimetallic clusters are converted to anionic surface species by simple deprotonation via 0 on dehydrated MgO or AI2O3 surfaces these species have been characterized by IR spectroscopy (119). The ionic interaction with surface cations such as AF and Mg is demonstrated by IR and NMR measurements. The surface polynuclear carbonyl anions are stable up to about 373 K. If heated in vacuo at higher temperature, extensive decomposition takes place to give a mixture of Ru (or Os) metal particles and Fe oxides, accompanied by the evolution of H2, CO, and CO2. 

The binuclear carbonyl Fe2(CO)9 is obtained as orange mica-like plates by photolysis of Fe(CO)5 in hydrocarbon solvents. The green Fe3(CO)12 is best made by acidification of a polynuclear carbonylate anion (see below) which in turn is obtained from Fe(CO)5 by the action of organic amines such as triethylamine. 

There is also a polynuclear carbonylate anion, [Fe6(CO)16C]2, which incorporates a carbon atom.26 The C atom resides in the center of an octahedron of iron atoms. 

The nucleophilic displacement of halide ions from M—X bonds by carbonylate anions (either mononuclear or polynuclear) is a general synthetic route to metal-metal bonded species (1,2), and numerous hetero-Pt clusters have been obtained in this way. The resulting products are not often those of expected stoichiometry, although under optimized experimental conditions this method can provide very useful syntheses, particularly of high-nuclearity clusters. Some examples are shown in Eqs. (7)—(11) (5,51-54). 

The compound Na2 [Rh12(CO)30] can be prepared by reaction of Rh2(CO)4-Cl2 with sodium acetate in methanol under an atmosphere of carbon monoxide.1 It contains one of the fust polynuclear anions to be formed when the rhodium carbonyls or carbonyl halides are reduced by the action of alkaline reagents in alcohols or by alkali metals in tetrahydrofuran (THF). It provides a unique example of a double octahedral cluster carbonyl anion in which the noble gas rule is not obeyed,1 2 and it is a starting material for the preparation of other polynuclear rhodium carbonyl anions.1 3"5 The synthesis reported here is a modification of the original method. The starting material is Rh4(CO)i2, now easily prepared at atmospheric pressure.6"8 The reaction is fast, and the overall procedure requires about 6-7 hours with 80-85% yields. 

The synthesis of HNCC by redox condensation involves the reaction of an anionic mononuclear or polynuclear carbonyl species with a neutral, cationic, or even anionic fragment. 

Some compounds and their reactions have been noted in Section 18-G-2. The homoleptic carbonyls are clusters such as M4(CO)i2 and M6(CO)i8. The hydride, HRh(CO)4, is very much less stable than HCo(CO)4 and has been made only under ca. 1400 atm pressure since it readily loses H2 to give clusters. Both Rh and Ir give anions [M(CO)4] and [M(CO)3]4 as R3NH+ salts as well as various cluster anions such as [Ir8(CO)22]2 and [Rh5(CO)i5] . Hydrido and other substituted polynuclear carbonyls are known. 

Duward F. Shriver et al. Reduction of carbon monoxide to methane by protonation of a polynuclear metal carbonyl anion, [Fe4(CO)i3] ... 

The di- and polynuclear metal-carbonyl complexes are readily redueed by Na-Hg to monometallic metal-carbonyl anions, their redox potentials usually being between -0.7 V and —1.7 V relative to FeCp2 [42], i.e. well below the redox potential of Na/ Hg(-2. 36 V relative to FeCp2 in non-aqueous solvents [43]). Redox potentials of a number of these complexes are listed in Table 7. 

In Bi- and Polynuclear Metal Carbonyl Anions and Carbonyl Hydrides 9.2.4.2.I. By Reactions of Monomeric Carbonyls. 

Metal elusters are synthesized by this method. Either mononuclear metal carbonyl anions or polynuclear metal carbonyl anions with metal halides may be used ... 

Addition of Ni(CO)3(C5H5N) converts the dinuclear anion into polynuclear carbonyl-nickelates. 

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