Ruthenium complexes with iron

In view of the protonation and reduction process it is instructive to compare results for Fe(II) compounds with the corresponding data for the positively charged Fe(III) analogues. Iron and ruthenium complexes with two metal centers should be investigated. While the iron complexes model particular features of the FeMo-cofactor in nitrogenase, the ruthenium analogues are analyzed because of their... 

This type of sandwich complex, first reported with iron as the central metal, has now become widespread with ruthenium as well. Early routes to ruthenium complexes were modeled on iron chemistry, and used the AICI3-catalyzed exchange of a cyclopentadienyl ligand for an arene in ruthenocene, or reaction of CpRu(CO)2Cl with AlCb/arene. These methods are less successful with ruthenium than with iron, however, owing to the greater stability of ruthenocene. A mixture of arene, pentamethylcyclopentadiene, and RuCls in the Zn reduction method gives good yields of the mixed-sandwich cations. A... 

A very pronounced synergistic effect is found for binary ruthenium-iron carbonyl catalysts in the water-gas shift reaction. Both mixed ruthenium-iron clusters and mixtures of ruthenium clusters with iron complexes are considerably more active in basic solutions. Whereas the water-gas shift activity (moles of H2 per mole of complex per day) of alkaline aqueous ethoxyethanol solutions of Ru3(CO)12 and Fe(CO)j is... 

The (benzo)pyridazines are able to form complexes with a variety of metal ions, and examples of complexes with iron (Section 6.01.3.2.1) and with silver and ruthenium (Section 6.01.12.6) are given. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Ruthenium(IV) produces few other complexes of interest but osmium(IV) yields several sulfito complexes (e.g. [0s(S03)6] and substituted derivatives) as well as a number of complexes, such as [Os(bipy)Cl4] and [Os(diars)2X2] (X = Cl, Br, I), with mixed halide and Group 15 donor atoms. The iron analogues of the latter complexes (with X = Cl, Br), are obtained by oxidation of... 

This is the second of the common oxidation states for iron and is familiar for ruthenium, particularly with Group 15-donor ligands (Ru probably forms more nitrosyl complexes than any other metal). Osmium(II) also produces a considerable number of complexes but is usually more strongly reducing than Ru". 

In accordance with FMO theory predictions,273 C2 —C4is the preferred modeofcycloaddition of tricarbonyliron and -ruthenium complexes of methyl l//-azepine-l-carboxylate with ethenetetracarbonitrile,222,274 hexafluoroacetone,222 and 2,2-bis(trifluoromethyl)ethene-l,l-dicarbonitrile 222 however, with ethenetetracarbonitrile, tricarbonyl[f/4-l-(ethoxycarbonyl)-1/f-azepine]iron(0) (1) yields a 1 6 mixture of the predicted C2 —C4 exo-adduct 2 and the C2 — C7 [6 + 2] 7i-cycloadduct 3,222 the latter heing formed by rearrangement of the former.274 Mixtures of the two adducts are also obtained with the tricarbonyliron complexes of 3-acetyl-l//-azepine and its l-(ethoxycarbonyl) derivative.274... 

Complexes containing encapsulated metal ions (clathrochelates ) with the formula [M(dioxime)3(BR)2] are known with iron(II) 135, cobalt(ll) 136, cobalt(III) 137, and ruthenium(ll) 138 (Fig. 37) [205-220]. Generally, these macrobicyclic complexes are prepared by template synthesis from a mixture of... 

A correlation of isomer shift, electronic configuration, and calculated -electron densities for a number of ruthenium complexes in analogy to the Walker-Wertheim-Jaccarino diagram for iron compounds has been reported by Clausen et al. [ 127]. Also useful is the correlation between isomer shift and electronegativity as communicated by Clausen et al. [128] for ruthenium trihalides where the isomer shift appears to increase with increasing Mulliken electronegativity. 

Many carbonyl and carbonyl metallate complexes of the second and third row, in low oxidation states, are basic in nature and, for this reason, adequate intermediates for the formation of metal— metal bonds of a donor-acceptor nature. Furthermore, the structural similarity and isolobal relationship between the proton and group 11 cations has lead to the synthesis of a high number of cluster complexes with silver—metal bonds.1534"1535 Thus, silver(I) binds to ruthenium,15 1556 osmium,1557-1560 rhodium,1561,1562 iron,1563-1572 cobalt,1573 chromium, molybdenum, or tungsten,1574-1576 rhe-nium, niobium or tantalum, or nickel. Some examples are shown in Figure 17. 

Au-B bonds are also present in metal clusters with intersticial or peripheral boron atoms. An example is the cluster [Fe4(CO)12BH(AuPPh3)2], which was prepared by reaction of [AuCl(PPh3)] with the carbonyl iron dihydride. With the oxonium salt the reaction proceeds to the trinuclear gold derivative [Fe4(CO)12B(AuPPh3)3] (357).2063-2070 The ruthenium analogues and complexes with other ligands have been also synthesized as, for example, (358).2071-2079... 

These reports sparked off an extensive study of metalloporphyrin-catalyzed asymmetric epoxidation, and various optically active porphyrin ligands have been synthesized. Although porphyrin ligands can make complexes with many metal ions, mainly iron, manganese, and ruthenium complexes have been examined as the epoxidation catalysts. These chiral metallopor-phyrins are classified into four groups, on the basis of the shape and the location of the chiral auxiliary. Class 1 are C2-symmetric metalloporphyrins bearing the chiral auxiliary at the... 

Barrau and coworkers have synthesized a series of iron and ruthenium complexes by irradiation of Me2HGe(CH)KGeMe2H and Me2HGe(CH)K SiMe2H (n = 1, 2) in the presence of Fe(CO)5 and Ru3(CO)i293. In each case irradiation causes CO loss, with the formation of the M(CO)4 species (reaction 43). When n = 2 the products are photostable with n = 1 (65) a mixture of products (66-69) are obtained due to secondary photolysis (reaction 44). The mechanism, outlined in Scheme 23, is presented to explain these observations. 

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. 

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