Hydrogen tris ruthenium

Tris-m-sulfonatophenylphosphine (tppts) plays an important role in the history of homogeneous catalysis [39], mainly due to its use in the Ruhrchemie/Rhone-Poulenc hydroformylation process [40], now operated by Celanese (see 1.2 and Chapter 7). It is also used in a number of fine chemical processes, such as selective hydrogenation with ruthenium [41], carbon-carbon bond formation with rhodium [42], and the Heck reaction [43]. Monosidfonated triphenylphosphine (tppms) is used for the preparation ofnonadienol [44] (see Figure 5). 

Ruthenium, tris(bipyridyl)-in hydrogen production from water, 6, 500, 506 in photochemical hydrogen production from water, 6. 499-510,502-506... 

Nagashima reported the hydrogenation of di-, tri- and tetranuclear ruthenium complexes bearing azulenes below 100 °C revealed that only the triruthenium compounds reacted with H2 via triruthenium dihydride intermediates.398 This indicates that there exists a reaction pathway to achieve facile activation of dihydrogen on the face of a triruthenium carbonyl moiety.399... 

Effect of Solvent and Base on the Ruthenium Carbonyl/Tri-methylamine System. Solvent plays an important role in the rate of hydrogen production. The ideal solvents are tetrahydrofuran, diglyme, and dimethoxyethane. Alcohols are only slightly less effective. Apparently the solvent must be miscible with water, promote ion formation, and be capable of weakly coordinating with the coordinately unsaturated species formed in the course of the reaction. 

Besides the electrochemical application, the (Cp )Rh(bpy)-complex 9 can also be used to reduce cofactors with hydrogen. In a recent study it was compared with ruthenium complex 13 [RuC12(TPPTS)2]2 (TPPTS tris(w-sulfonatophenyl)-phosphine Scheme 43.5). Both complexes were used to regenerate the cofactors in the reduction of 2-heptanone to (S)-2-heptanol, catalyzed by an ADH from Thermoanaerobium brockii (TfrADH) [46, 47]. The TON for both catalysts was 18. 

The parent carbonyls, M COlu (M = Ru, Os), have not been isolated, but the related hydrides H2M4(CO)13 and HJVtjCCO) have been prepared for both ruthenium and osmium by direct reaction of the tri-nuclear carbonyl with hydrogen or water (see Section III,C) (82, 86). 

A comparison has been made of the structural parameters and hydrogen bonding in [Ru"Cl2L(HL)r and [Ru Cl2L(HL)] where HL = (226), and the crystal structure of tris (dimethylglyoxime)ruthenium(II) dichloride has been determined. ... 

Many catalysts, certainly those most widely used such as platinum, palladium, rhodium, ruthenium, nickel, Raney nickel, and catalysts for homogeneous hydrogenation such as tris(triphenylphosphine)rhodium chloride are now commercially available. Procedures for the preparation of catalysts are therefore described in detail only in the cases of the less common ones (p. 205). Guidelines for use and dosage of catalysts are given in Table 1. 

Dodecacarbonyltriruthenium can be prepared by several methods. Johnson and Lewis1 have reported a procedure in which ruthenium trichloride hydrate is converted to tris(2,4-pentanedionato)ruthenium(III), which is turn is reacted with hydrogen and carbon monoxide. Reaction pressure and temperature are high (160 atm and 165 °C) and the yield is in the range from 50 to 55%. 

Mechanism 2 requires deprotonation of a ligand, and dissociation of the hydrogen bound to the C(3) atom was suggested to be the slow step for the reaction of tris(2,2 -bipyridine)ruthenium(III) in base (12). This would require a mechanism for the 1,10-phenanthroline complexes different from that of the 2,2 -bipyridine complexes, but, from the data in Table II as illustrated in Figs. 3-5, this seems unlikely. The requirement of a different mechanism is based upon the significant differences in rates of D/H exchange as measured by 1H NMR for the tris(diimine)... 

Several chemical techniques have also been developed, such as simple oxidation using hydrogen peroxide or lead tetraacetate.77 Both these protocols suffer from harsh reaction conditions and additional toxicity issues. A more functional group-tolerant method is the use of tris(hydroxy-methyl)phosphine to coordinate the ruthenium.78 This complex is water soluble and can be washed from the product by several simple water washes. The main drawback to this method is the large excess of phosphine needed (25 mole equiv./mole of Ru).46... 

The early preparations gave poor yields but highly efficient methods have been developed recently. Optimum yields are obtained by the method of Pino and his coworkers9 in which tris(2,4-pentanedionato)ruthenium(III) is treated with equimolar mixtures of hydrogen and carbon monoxide at moderate temperatures and pressures (140-160°, 200-300 atmospheres). However, this method is limited by the availability of the tris-(2,4-pentanedionato)ruthenium(III) which is obtained in only low yields from the readily available ruthenium trichloride hydrate. The method given here is a modification on the Pino method. 

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