Ruthenium complexes hydrido

Keywords hydrido complex, ruthenium, tautomerization, vinylidene complex... 

The first reported interaction between a C—H bond in a ligand and a soluble transition metal complex was that reported by Chatt and Davidson (5). The reaction product from the reaction of sodium naphthalene with (rans-dichlorodi-(dmpe)ruthenium(II) (I) (dmpe = 1,2-bisdimethylphosphinoethane) was found to be a tautomeric equilibrium mixture of the ruthenium(O) complex (II) that contains a 7r-complexed naphthalene ligand and the ruthenium(II)-hydrido complex (III) where a C(2)—H bond has added to the ruthenium ... 

This then was the first report of a compound in which alkyl C—H bond activation by a transition metal had occurred. In the solid state, this equilibrium is also in favor of the hydrido complex (V), and its crystal structure has recently been determined (15). It shows compound V to be a dimer (VI), the oxidative addition of the methyl group of a ligand on each ruthenium atom being to a second ruthenium atom. Presumably one reason why this occurs is because the product of intramolecular ring closure would contain a highly strained three-membered Ru—P—C ring (i.e., in monomer V). 

Finally, the unusual ruthenium hydrido complex HRu(PPh3)3[HC=C(Me)C(0)0C4H9] is formed in the reaction between H2Ru(PPh3)4 and n-butylmethacrylate77). The Ru atom has oxidatively added to a vinylic C-H bond, and this compound represents the first example of such a structure. 

The feverish interest in hydrido complexes has, as its main cause, the tremendous potential of these reactions in catalytic systems. In a relatively short span of time, hydrido complexes have been found to play a role in a significant number of catalytic processes (6, 9)—e.g., oligomerization of olefins (rhodium), decarboxylation reactions (rhodium), and hydrogenation reactions (ruthenium, osmium, rhodium, iridium, and platinum). Discussion of these applications would go beyond the scope of the present treatment. 

Binuclear [RuX2(arene)]2 (1) and mononuclear RuX2(L) (arene) (3) derivatives have been shown to be useful precursors for access to alkyl-or hydrido(arene)ruthenium complexes. The latter are key compounds for the formation of arene ruthenium(O) intermediates capable of C—H bond activation leading to new hydrido and cyclometallated ruthenium arene derivatives. Arene ruthenium carboxylates appear to be useful derivatives of alkyl-ruthenium as precursors of hydrido-ruthenium complexes their access is examined first. 

J. Chatt, and J. M. Davidson, The Tautomerism of Arene and Ditertiary Phosphine Complexes of Ruthenium(O), and the Preparation of New Types of Hydrido-Complexes of Ruthenium(II), J. Chem. Soc. 1965, 843-855. 

The corresponding hydrido/alkyl (and aryl) complexes v-[RuHR(L-L), ] (L-L = dppe, dppm, dmpe R = Me, Et, Ph) are readily prepared from m-[RuClR(L-L)2] and Li[AlH4]1659 whereas treatment of cis- or tvans-[RuCl2 (dmpe)2 ] with arene radical anions affords d.v-[RuH(f 1-aryl)(dmpe)2] (aryl = phenyl, 2-naphthyl, anthryl, phenanthryl).1389 In solution, these compounds are in tautomeric equilibria with significant concentrations of Ru° complexes (e.g. equation 148) although X-ray analysis for aryl = 2-naphthyl confirms the presence of the six-coordinate Ru" species (373) in the solid state.2459 Some reactions of (373) with various substrates to produce other hydrido complexes are shown in Scheme 74.44>24m Note that the compound of empirical formula [ Ru(dmpe)2 ] obtained by pyrolysis of [RuH(2-np)(dmpe)2] (reaction (iv) Scheme 74) is a binuclear Ru" hydrido complex, resulting from intermolecular oxidative addition of methyl groups to ruthenium.1390... 

There are relatively few examples of anionic ruthenium hydrido complexes. Thus, several papers have discussed the preparation of the [RuH6]4 ion from Ru, H2 and various lanthanide dihydrides at 800°C.2490,2491 The 99Ru Mossbauer spectra at 4.2 K for various M2[RuH6] (M = Ca, Sr, Eu, Y) are consistent with diamagnetic Ru11 centres.2492... 

Ruthenium clusters with even higher nuclearity have also been isolated. When (1) is refluxed in ethanol for 18h, the hexaruthenium hydrido complexes [HRu6(CO)i8] (18) and [H2Ruio(CO)25] (19) are produced, along with metallic ruthenium (equation 8). The dihydride complex (19) represents the first noncarbido decaruthenium cluster. A trianion with 11 ruthenium centers (20) is synthesized by thermolysis of (1) in undried acetonitrile (equation 9), and... 

Hydrido complexes, gold-osmium, 27 209 iridium, 26 117, 27 19 iron, 26 244, 27 168 iron-tungsten, 26 336 manganese, 26 226 mercury-molybdenum-ruthenium,... 

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