Ruthenium complexes carbide

Subsequent research eventually led to the preparation of neutral carbide complexes. The first of these to be reported was the trigonal bipyramidal ruthenium complex illustrated in Figure 6-7, prepared from a carbene complex via the following reaction 20... 

The chemistry of these compounds has not been investigated in detail. Scheme 12 summarizes some of the chemistry that has been established for the ruthenium complex RueC(CO)i7 (192). In general, the octahedral metal-carbide skeleton is maintained, substitution reactions occurring with phosphine, phosphites, and arsine ligands. Base attack leads to the production of the anion [RugC(CO)i6] , which is... 

There are two well-characterized examples of a naked carbon atom bound by a triple bond to a metal center (Fig 14.3.8). The molybdenum carbide anion [CMo N(R)Ar 3]- (R = C(CD3)2(CH3), Ar = C6H3Me2-3,5), an isoelectronic analog of NMo N(R)Ar 3, can be prepared in a multistep procedure via deprotonation of the d° methylidyne complex HCMo N(R)Ar 3. The Mo=C distance of 171.3(9) pm is at the low end of the known range for molybdenum-carbon multiple bonds. In the diamagnetic, air-stable terminal ruthenium carbide complex Ru(=C )C12(LL/)(L = L = PCy3, or L = PCy3 and L = l,3-dimesityl-4,5-dihydroimidazol-2-ylidene), the measured Ru-C distance of 165.0(2) pm is consistent with the existence of a very short Ru=C triple bond. 

Although Heppert s discovery and the subsequent work by Grubbs and others has received special attention, it must be emphasized that prior to the studies on ruthenium carbido complexes Christopher Cummins from MIT had reported the preparation of the anionic molybdenum carbide [CMo N(R)Ar 3] (R =... 

R. G. Carlson, M. A. Gile, J. A. Heppert, M. H. Mason, D. R. Powell, D. Yander Velde, and J. M. Vilain, The Metathesis-Facilitated Synthesis of Terminal Ruthenium Carbide Complexes A Unique Carbon Atom Transfer Reaction, J. Am. Chem. Soc. 124, 1580-1581 (2002). 

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

C, Carbide, iron complex, 26 246 ruthenium cluster complexes, 26 281-284 CHFiO, Acetic acid, trifluoro-, tungsten complex, 26 222... 

The metal-carbon bond distance in carbide complexes is generally quite similar to the comparable distances in alkylidyne complexes. For example, the Ru—C distance in the ruthenium carbide complex in Figure 6-7, 165.0 pm, is nearly identical to that in [RuCl2(=CCH2Ph)(PR3)]+ (R = isopropyl), 166.0 pm, also shown in Figure 6-7. 

As mentioned in the Introduction, we can distinguish simple FT catalysts, producing hydrocarbons exclusively with ruthenium as the outstanding example, and complex FT catalysts, such as promoted iron, wherein the steady-state metallic, oxidic, and carbidic phases can coexist. With the latter catalysts the product is a cocktail containing various oxygenates, in particular primary alcohols, as well as hydrocarbons. 

Further investigations are needed to clarify this point. It shonld also be noted that when the homobimetallic ruthenium-ethylene complex 4 was treated with a stoichiometric amount of acetylene in THF, the p-carbide complex 11 was formed, presumably via the intermediate ratheninm-vinyhdene complex 10 (Scheme 6) (75). 

Materials. Zeolites A, X, Y, and L were from Union Carbide Corporation, and Zeolite Z was a synthetic large port mordenite from Norton Company. Chabasite was a crystallographically very pure natural zeolite from an Hungarian deposit. Zeolite Y is an aluminum-deficient Y zeolite prepared by H4EDTA treatment. The hexammine complex of was from Strem Chemicals. The ruthenium-on-alumina catalyst was from Ventron. 

Table 3 X-ray structural data for carbene and carbide complexes of ruthenium and osmium porphyrin carbenes...

C, Carbide, iron complex, 26 246 ruthenium cluster complexes, 26381-284 CHF3O3S, Methanesulfonic add, trifluoro-, iridium, manganese, and rhenium com-iriexes, 26 114,115,120 platinum complex, 26 126 CHOS2, Dithioaubonic add, 27 287 CH2> Methylene, osmium complex, 27 206 CH2O2, Formic add, rhenium complex, 26 112... 

Exclusive of metal-metal bonding, the six metal atoms in the octahedral cluster metal carbonyls Mg(CO)10 (M = Co, Rh, and Ir) as well as their iso-electronic analogs Me(CO)i52 and Mg (CO) have (6)(9) + (2)(16) = 86 outer valence electrons. The hydride H2Rug(CO)i0 and the carbide Rug(C0)i7C are two types of octahedral cluster ruthenium carbonyl complexes that likewise have 86 outer valence electrons exclusive of metal-metal bonding and thus may be regarded as isoelectronic with Mg(CO) g (M = Co, Rh, and Ir). 

Similarly, Fischer carbene complexes are formed when Grubbs systems react with vinyl esters, vinyl carbonates, and vinyl halides. However, these Fischer car-benes are known to decompose to give terminal ruthenium carbide species by elimination of HX (X = OjCR, OjCOR, halide) [83-86]. Notably, the formation of the carbide complexes is less favorable in phosphine-free systems, which enables the Hoveyda [56] and Piers [87] catalysts to promote the cross metathesis of vinyl hahdes and terminal or internal olefins [88]. 

The generation of the catalytically active 14-electron species is an important factor for the improvement of catalyst activity. A true 14-electron complex with no free L ligand has been reported by Piers et al. [24]. This phosphonium-aUcylidene complex 14 was obtained by protonation of ruthenium carbide intermediates and isolated in 87-95% yield (Scheme 6). 

The same kind of observation was made recently by D. Dombeck [31] of Union Carbide for the same reaction using ruthenium clusters. In the case of ruthenium there is, under catalytic conditions, evidence for the presence of [HRu3(CO)ii] HRu(CO)4 and Ru(CO)3lJ. An almost complete catalytic cycle has been established by Dombeck. It appears that the hydrido anionic cluster [HRu3(CO)ii]" or HRu(CO)7 make a nucleophilic attack at CO coordinated to the mononuclear carbonyl Ru(II) complex to give a formyl species. The reaction, here, would obey a very complex mechanism involving both mononuclear and polynuclear species. This phenomenon seems to be a general rule in many reactions involving CO. 

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