Ruthenium diphosphine complexes

More recently, examination of the cycloisomerization of l,l,2,2-tetramethyl-l,2-divinyldisilane 130 in the presence of a ruthenium-diphosphine complex <2005JOM3451>, ruthenium-DPPE, revealed a selective catalysis and l,l,2,3,3-pentamethyl-l,3-disilacyclopent-4-ene 132 was isolated as the major product, in addition to 131 (DPPE = bis(diphenylphosphino)ethane Equation 22). 

For ruthenium, special precursors are required to synthesize defined bidentate diphosphine complexes. With Taniaphos for instance, it is possible to synthesize such complexes starting from unusual rathenium(ll) species. The complexes were characterized by NMR and single crystal analysis. 

In summary, the asymmetric hydrogenation of olefins or functionalized ketones catalysed by chiral transition metal complexes is one of the most practical methods for preparing optically active organic compounds. Ruthenium and rhodium-diphosphine complexes, using molecular hydrogen or hydrogen transfer, are the most common catalysts in this area. The hydrogenation of simple ketones has proved to be difficult with metallic catalysts. However,... 

Platinum(II) and ruthenium(II) complexes with chiral modified diphosphines like 47 or tetradentate P2N2 ligands like 48 have been used for the asymmetric epoxidation of olefins with hydrogen peroxide with ee values of 18-23%, which increased up to 41% when cationic solvato derivatives such as P2Pt(CF3)(CH2Cl2)(BF4) are used . Similar chiral inductions were reported for Ru derivatives, although the nature of the active intermediate was still in question. ... 

Ruthenium(II) complexes bearing atropisomeric diphosphine ligands have proved to be efficient systems for the hydrogenation of a wide range of prochiral substrates. A new catalytic system has been developed based on ruthenium complexes having SYNPHOS and DIFLUORPHOS as chiral diphosphanes (Figure 3.6). 

Lenero, K.A., Kranenburg, M., Guari, Y., Kamer, P.C.J., van Leeuwen, P.W.N.M., Sabo-Etienne, S. and Chaudret, B. (2003) Ruthenium dihydrogen complexes with wide bite angle diphosphines. Inorg. Chem., 42, 2859. 

Preparation of the JST class (see Section 12.3.4) of the ruthenium-diphosphine-diamine complex, [(PhanePhos)Ru(diamine)Cl2], produced highly active and enantioselective catalysts in the reduction of aryl methyl ketones (128, R = Me), as well as a,P-unsaturated ketones.162-163 Higher... 

An interesting synthesis of the cyclopentadienyl bisphosphine ruthenium nitrosyl complex 9 involves the thermal displacement of both phenyl groups from (i75-C5H5)Ru(NC))PIi2 (8) with a chelating diphosphine [Eq. (6)] (72). Infrared data indicate that the nitrosyl ligand is linear (3 e ... 

The chemistry of ruthenium (II) complexes incorporating P-donor ligands, particularly phosphines and diphosphines, is flourishing. This class of compounds has given rise to a versatile organometallic reactivity. They are also found in many catalytic cycles, but decoordination of the phosphine from the coordination sphere of the metal is often required for the catalysis to proceed. 

Reductively induced alterations from cumulenic to alkynyl resonance structures have been observed for mononuclear and dinuclear ruthenium allenylidene complexes. The half-wave potentials for the one-electron reduction of allenylidene complexes [ Ru = C = C = C(ER )(R )] ( Ru = trun.s-Cl(L2)2Ru L2 = chelating diphosphine ER = NR2, SR, SeR, aryl, alkyl R = aryl, alkyl) strongly depends on the nature of the ER substituent. Amino- and aryl-substituted congeners with reduction potentials of ca. -2.2 V and -1.0 V, respectively, constitute the two extremes within this series. These sizable potential... 

Asymmetric hydrogenation was boosted towards synthetic applications with the preparation of binap 15 by Noyori et al. [55] (Scheme 10). This diphosphine is a good ligand of rhodium, but it was some ruthenium/binap complexes which have found spectacular applications (from 1986 up to now) in asymmetric hydrogenation of many types of unsaturated substrates (C=C or C=0 double bonds). Some examples are listed in Scheme 10. Another important development generated by binap was the isomerization of allylamines into enamines catalyzed by cationic rhodium/binap complexes [57]. This reaction has been applied since 1985 in Japan at the Takasago Company for the synthesis of (-)-menthol (Scheme 10). 

Ruthenium carborane complexes 1-8, were synthesized under argon using anhydrous solvents, according to procednres described in the literatnre (14-16). Coimnercial phosphines and diphosphines (Strem Chemicals) were nsed. The obtained prodncts were isolated and pnrified by colnnrn chromatography nsing silica gel Merck (230 00 mesh). 

Additional catalyst development identified the positive effect of 1,2-diamines as additives in the (BlNAP)Ru(OAc)2-catalyzed enantioselective hydrogenations of ketones [24], This discovery ultimately led to the synthesis of a class of (diphosphine) Ru(diamine)X2 (X = H, halide) compounds [25] (Figure 4.1) which have emerged as some of the most active and selective hydrogenation catalysts ever reported [26]. Mechanistic studies by Noyori [14] and Morris [27] have established bifunctional hydrogen transfer to substrate from the cis Ru-H and N-H motifs and identified the importance of ruthenium hydridoamido complexes for the heterolytic splitting of H2. This paradigm allows prediction of the absolute stereochemistry of the chiral alcohols produced from these reachons. 

First results with polymer-supported rhodium(I) chiral diphosphine complexes were published by Ohkubo, " but the optical selectivity reported was rather moderate (7.7% e.e.). Chiral ruthenium catalysts have also been successfully used, and the results were compiled in a review published in 1981. ... 

Monophosphines can be used as promoters, but the promoting effect is small. Chelating diphosphines have a much higher promoting efficiency. if) Phosphine-substituted trinuclear clusters can be used as catalyst precursors, but conversions are lower than when Ru3(CO)i2 and the phosphine are added separately [154]. Conversely, the use of preformed mononuclear ruthenium-phosphine complexes affords the best results [178, 180]. The role of mononuclear species as the active catalysts is strongly implied and has also been confirmed by a detailed mechanistic study (see Chapter 6). 

Zimmer-De, I. M. Morris, R. H. Kinetic hydrogen/deuterium effects in the direct hydrogenation of ketones catalyzed by a well-defined ruthenium diphosphine diamine complex. /. Am. Chem. Soc. 2009,131,11263-11269. 

Gao, J.-X. Ikariya, T. Noyori, R. A. Ruthenium(II) Complex with a Cj-Symmetric Diphosphine/Diamine Tetradentate Ligand for Asymmetric Transfer Hydrogenation of Aromatic Ketones. Organometallics 1996, 15, 1087-1089. 

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