Iron compounds ruthenium carbonyls

High selectivity is observed, and in aromatic compounds other substituents (C02R, OR, CN, halide) are not affected. Dinitro aromatics could be sequentially hydrogenated to nitroamines and diamines (105). [Some ruthenium and iron carbonyls were less effective (104)]. 

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

Table 8.4 Mono- and bimetallic iron- ruthenium- and osmium-based catalysts prepared from carbonyl compounds and used in the CO hydrogenation reaction.

It is also relevant to record that several iron-carbonyl complexes with bridging, and in one case terminal, aryltellurol ligands have been prepared by reaction of Fe(CO)5, Fe(CO)12 or [ji-CpFe(CO)2]2 with diaryl ditellurides and which, together with complexes containing other transition metal carbonyls, e.g, ruthenium, osmium and manganese, provide a substantial number of interesting compounds.2... 

In the past, this field has been dominated by ruthenium, rhodium and iridium catalysts with extraordinary activities and furthermore superior enantioselectivities however, some investigations were carried out with iron catalysts. Early efforts were reported on the successful use of hydridocarbonyliron complexes HFcm(CO) as reducing reagent for a, P-unsaturated carbonyl compounds, dienes and C=N double bonds, albeit complexes were used in stoichiometric amounts [7]. The first catalytic approach was presented by Marko et al. on the reduction of acetone in the presence of Fe3(CO)12 or Fe(CO)5 [8]. In this reaction, the hydrogen is delivered by water under more drastic reaction conditions (100 bar, 100 °C). Addition of NEt3 as co-catalyst was necessary to obtain reasonable yields. The authors assumed a reaction of Fe(CO)5 with hydroxide ions to yield H Fe(CO)4 with liberation of carbon dioxide since basic conditions are present and exclude the formation of molecular hydrogen via the water gas shift reaction. H Fe(CO)4 is believed to be the active catalyst, which transfers the hydride to the acceptor. The catalyst presented displayed activity in the reduction of several ketones and aldehydes (Scheme 4.1) [9]. 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Unstable metal nitrosyls are formed by Fe, Ru and Ni. Black Fe(NO)4, made by heating iron carbonyl with NO under pressure at 50°, is the most stable. The structure is unknown, but the ionic formula NO+[Fe(NO)3] has been suggested to explain its low volatility. Ruthenium tetranitrosyl, Ru(NO)4, is made as cubic, red crystals when NO is passed into Ru2(CO)g. A compound of empirical formula Ni(NO)2 is obtained as a blue powder when NO is passed into Ni(CO)4 dissolved in CHCI3. 

Several other examples of intramolecular ruthenium-, copper-, rhodium- and iron-catalyzed cyclizations via carbometalation with polyhalocarbons are known, with a range of stereoselectivities25 4 49. Similarly, palladium-catalyzed intramolecular ene-halogenocyclization" of unsaturated a-iodo carbonyl compounds, using Pd(dppe)2, has been applied to heterocyclic synthesis26 29. 

The reactions of iron carbonyls with diorgano tellurides deserve mention, for example the reaction of Fe3(CO),2 with PhjTe gives Ph2TeFe(CO>4, whilst several ruthenium-carbonyl complexes have been prepared from reactions between diphenyl telluride and alcoholic carbon monoxide-saturated solutions of ruthenium trichloride hydrate. Various other ruthenium-carbonyl complexes of diorgano teUurides, including di- and tri-substituted species, have also been described. The utility of diphenyl telluride in transition metal carbonyl chemistry has also been well illustrated during studies of manganese and rhenium compounds. 

Fig. 12 Carbon monoxide releasing compounds a manganese decacarbonjd b tricar-bonjdruthenium chloride dimer c a ruthenium-glycinate complex d iron carbonyl nucleoside analogues, TDSO = thex)4dimeth)4sil)4oxy...

Anions of iron carbonyls form, with few exceptions, the only anionic carbonyl compounds known for this group of metals. One ruthenium carbonyl anion, [C5HsRu(CO)2] , has been investigated. Osmium appears to have been completely neglected in this area of carbonyl chemistry. 

Photochemical Activation. Coordinative unsaturated fragments may also be produced by photolytic reactions. In presence of UV-irradiation metal carbonyl compounds lose sequentially CO-ligands. Electron-deficient, solvent coordinated species produced in this way may combine with inactivated metal complexes via the formation of donor-acceptor metal-metal bonds. Iron, ruthenium, and osmium trinuclear carbonyl clusters may be prepared by this way ... 

Many metal clusters are air-stable compounds. However those of the first transition metal series are in general more sensitive to air. Thus, binary carbonyl of ruthenium, rhodium, and iridium are rather air-stable species while those of iron, Fe3(CO)i2, and cobalt, Co4(CO)i2, rapidly decompose apparently via formation of the carbonates. 

In basic solution Fe(CO)6 and M(CO) (M = Cr, Mo, or W) catalyse the water-gas shift reaction (i.e. HgO + C0 C02 + H2). Ruthenium carbonyl compounds catalyse this reaction in both basic and acidic media mixed ruthenium-iron carbonyl catalysts e.g. [FeRu3H2(CO) 3] are considerably more active in basic solution than either ruthenium or iron carbonyls alone. [PtLg] (activity L = PPr 3>PEt3>PPh3) and KaPtCl4-SnCl4,5H20 also catalyse the water-gas shift reaction the proposed mechanism for the latter catalyst is shown in Scheme 1. ... 

We do not know exactly where the hydrogen binds at the active site. We would not expect it to be detectable by X-ray diffraction, even at 0.1 nm resolution. EPR (Van der Zwaan et al. 1985), ENDOR (Fan et al. 1991b) and electron spin-echo envelope modulation (ESEEM) (Chapman et al. 1988) spectroscopy have detected hyperfine interactions with exchangeable hydrous in the NiC state of the [NiFe] hydrogenase, but have not so far located the hydron. It could bind to one or both metal ions, either as a hydride or H2 complex. Transition-metal chemistry provides many examples of hydrides and H2 complexes (see, for example. Bender et al. 1997). These are mostly with higher-mass elements such as osmium or ruthenium, but iron can form them too. In order to stabilize the compounds, carbonyl and phosphine ligands are commonly used (Section 6). 

Hydrolysis of the ester forms adipic acid, used to manufacture nylon—6. Carbonylations of nitroaromatics are used to synthesize an array of products including amines, carbamates, isocyanates, ureas and azo compounds. These reactions are catalyzed by iron, ruthenium, rhodium and palladium complexes. For example, carhonylation of nitrobenzene in the presence of methanol produces a carbamate ... 

---