Ruthenium porphyrins complexation

Progress in investigation of ruthenium porphyrin complexes 97MI10. 

Over the last decade a number of high oxidation state ruthenium porphyrin complexes containing 0x0 or imido ligands have been reported and have been thoroughly studied for their role in oxidation and atom-transfer chemistry. Although comparisons can be drawn with organometallic species (carbene, imido. and 0x0 ligands are formally isolobal) the chemistry of the 0x0 and imido complexes is beyond the scope of the review and will not be covered here. 

Ruthenium porphyrin complexes are also active in cyclopropanation reactions, with both stoichiometric and catalytic carbene transfer reactions observed for Ru(TPP)(=C(C02Et)2> with styrene. Ru(Por)(CO)orRu(TMP)(=0)2 catalyzed the cyclopropanation of styrene with ethyidiazoacetate, with aiiti.syn ratios of 13 1... 

The preparation of cyclopropanes by intermolecular cyclopropanation with acceptor-substituted carbene complexes is one of the most important C-C-bond-forming reactions. Several reviews [995,1072-1074,1076,1077,1081] and monographs have appeared. In recent decades chemists have focused on stereoselective intermolecular cyclopropanations, and several useful catalyst have been developed for this purpose. Complexes which catalyze intermolecular cyclopropanations with high enantiose-lectivity include copper complexes [1025,1026,1028,1029,1031,1373,1398-1400], cobalt complexes [1033-1035], ruthenium porphyrin complexes [1041,1042,1230], C2-symmetric ruthenium complexes [948,1044,1045], and different types of rhodium complexes [955,998,999,1002-1004,1010,1062,1353,1401-1405], Particularly efficient catalysts for intermolecular cyclopropanation are C2-symmetric cop-per(I) complexes, as those shown in Figure 4.20. These complexes enable the formation of enantiomerically enriched cyclopropanes with enantiomeric excesses greater than 99%. Illustrative examples of intermolecular cyclopropanations are listed in Table 4.24. 

Asymmetric C-H amination has progressed through the apphcation of rathenium(II) porphyrin catalysts. Che has employed fluorinated ruthenium porphyrin complexes with added AI2O3 (in place of MgO) to catalyze suifamate ester insertion (Scheme 17.31) [98]. These systems show exceptional catalyst activity (>300 turnovers) and afford product yields that are comparable to rhodium tetracarboxylate-promoted reactions. Of perhaps greater significance is that the use of the chiral rathenium complex... 

In a subsequent report, in 2005 [55], the same group described the preparation of imprinted polymer capable of oxidising alcohols and alkanes with 2,6-dichlor-opyridine /V-oxide (86) without mineral acid activation. The polymer was imprinted with a ruthenium porphyrin complex (87) using the diphenylmethana-mine (88) as pseudo-substrate template in order to achieve a shape of the cavity complementary to the substrates, diphenylmethane (89) and diphenylmethanol (84). The reaction, carried out with the imprinted polymer on the diphenylmethanol as substrate, showed a rate enhancement 2.5 higher than with the non-imprinted polymer. In the same conditions, but with diphenylmethane and... 

Some examples of asymmetric epoxidations of alkenes using chiral ruthenium porphyrins have been reported for example, the previously reported D4-sym-metrical chiral ruthenium porphyrin complex Run(D4-Por )(CO)(MeOH) [58], which produced (R)-styrene oxide in 57% ee with Cl2PyNO as a donor, was readily converted into the dichloro derivative A [59] (Fig. 11). This di-chlororuthenium porphyrin gave (R)-styrene oxide in 69% ee using Cl2PyNO and was highly active (875 TON in 1.5 h). The use of unsubstituted pyridine N-oxide or NMO as oxidants resulted in low substrate conversions as well as... 

Thiazyl monomer can be stabihzed by coordination to a metal, and many thionitrosyl complexes with Cr, Mo, Re, Ru, Os, Co, Rh, Ir, and Pt are known. Comparison of the spectroscopic properties and the electronic stmctures of M-NS and M NO complexes indicates that NS is a better a-donor and jr-acceptor ligand than NO. Oxygen transfer from an NO2 to an NS ligand on the same metal center occurs in ruthenium porphyrin complexes. ... 

James et al. reported that aerobic oxidation of primary amines in the presence of a ruthenium porphyrin complex Ru(TMP)(0)2 (TMP = tetramesitylporphyrinato) gives nitriles (100%) (Eq. 3.31) [66]. 

A ruthenium porphyrin complex immobilized in a polymer can be used for catalytic epoxidation with 2,6-dichloropyridine N-oxide [112], Nitrous oxide (N2O) can be also used as oxidant for the epoxidation of trisubstituted olefins in the presence of ruthenium porphyrin catalyst [113], Asymmetric epoxidations have been reported using chiral ruthenium porphyrin complexes 35 [114], 36 [115], and 37 [116] (Eq. 3.62). 

H. Tanaka, K. Hashimoto, K. Suzuki, Y. Kitaichi, M. Sato, T. Ikeno, T. Yamada, Nitrous oxide oxidation catalyzed by ruthenium porphyrin complex. Bull. Chem. Soc. Jpn. T7 (2004) 1905. 

Another type of polymer-supported chiral catalyst for asymmetric cyclopropanation was obtained by electropolymerization of the tetraspirobifluorenylporphyrin ruthenium complex [143]. The cyclopropanation of styrene with diazoacetate, catalyzed by the polymeric catalyst 227, proceeded efficiently at room temperature with good yields (80-90%) and moderate enantioselectivities (up to 53% at -40 °C) (Scheme 3.75). PS-supported versions of the chiral ruthenium-porphyrin complexes 231 (Scheme 3.76) were also prepared and used for the same reaction [144]. The cyclopropanation of styrene by ethyl diazoacetate proceeded well in the presence of the polymeric catalyst to give the product in good yields (60-88%) with high stereoselectivities (71-90% ee). The highest ee-value (90%) was obtained for the cyclopropanation of p-bromostyrene. 

Rapid catalytic oxygenation of hydrocarbons with perhalogenated ruthenium porphyrin complexes... 

Highly efficient oxygenation reactions with ruthenium porphyrin complexes and aromatic 7V-oxides in the presence of strong mineral acids have been described by Hirobe et al. [4], We have recently reported that electron deficient perhalogenated ruthenium porphyrins catalyze the oxygenation of a variety of even unreactive substrates under mild conditions (40 - 65 C) in the presence of 2,6-dichloropyridine A -oxide in aprotic media [5]. Unusually high rates and turnover numbers (TO) were obtained. 

Very recently, Simmonneaux has reported that a chiral ruthenium-porphyrin complex is an active catalyst for cyclopropanation of styrene, but the corresponding cyclopropanes were produced with low to moderate enantiomeric excesses [52]. 

Nitrous oxide oxidation of olefins catalyzed by ruthenium porphyrin complexes. Chem. Lett. 3, 268-269. 

T. Carofiglio (1997). Rapid catalytic oxygenation of hydrocarbons with polyhalogenated ruthenium porphyrin complexes. Stud. Surf. Sci. Catal. 110, 865-872. 

The electrochemistry of bis-phosphine ruthenium porphyrin complexes has been reported (Scheme Oxidation of [Ru(porph)L2] (porph = OEP, TPP L - PPhj, PBu",) affords... 

Electron-deficient ruthenium-porphyrin complexes A and B have been used to catalyze intramolecular amidation reactions in sulfamates 183, to give cyclic products 184. When the chiral porphyrin B is employed, optically active products 184 are generated (Scheme 13 Table 5) <2002AGE3465>. 

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