J.J. Ziółkowski

The catalytic epoxidation of olefins with organic hydroperoxides

Abstract The metal catalyzed epoxidation reaction of olefins with organic hydroperoxides appeared to be particularly important not only from an industrial point of view (Halcon process) but also because of its wide application in synthetic organic chemistry. The number of catalytic systems containing transition metal complexes is considered, and the correlations between the structure and the reactivity of olefins and hydroperoxide are discussed. The mechanism of the catalytic epoxidation reaction is considered on the basis of an analogy with the noncatalytic epoxidation reaction and that with peracids. The function of the catalyst and the role of its transient forms, including the effect of solvent in the catalytic reaction, are discussed.

Low pressure, highly active rhodium catalyst for the homogeneous hydroformylation of olefins

Abstract Hex-1-ene hydroformylation was examined at pressures of 1–11 atm and 40 °C, using Rh(acac)[P(OPh) 3 ] 2 + P(OPh) 3 as catalyst. The highest efficiency of aldehydes was achieved employing a small P(OPh 3 ) 3 excess-[P(OPh) 3 ]:[Rh] = 2:1. For reactions carried out at 1 atm, very high n/iso ratios i.e. 10–80 were obtained. Pressure increase caused a systematic drop of the n/iso ratio to ca. 5 at 11 atm. Simultaneously with hydroformylation, isomerisation of hex-1-ene to hex-2-ene occurs, but the contribution of the latter declines with increasing pressure. IR examination of the reaction mixture revealed that HRh(CO)[P(OPh) 3 ] 3 was the active form of the catalyst. The same catalytic system was applied in propylene hydroformylation at 5–10 atm pressure and 40 °C. In such conditions the yield of aldehydes was 10–70%, with a n/iso selectivity of 2–10.

The effect of light and role of donor-acceptor interactions in olefin metathesis

Abstract The effect of light and role of donor-acceptor interactions on in situ catalyst formation in olefin metathesis reactions have been investigated in the system containing W(CO) 6 (electron donor and catalyst precursor) and various halides (electron acceptors). The reaction intermediates were identified by means of ESR, IR and electron spectroscopy; their role in the metathesis reaction was determined.

Homogeneous and alumina supported rhodium complex catalysed hydrogenation

Abstract The complex Rh (OH) (CO) (PPh3)in homogeneous as well as in γ-Al2O3 supported system was used as catalyst precursor for hex-1-ene and benzene hydrogenation at 80°C and 6.5 atm of H2. The hydride complexes, HRh (CO) (PPh3)3 and HRh (CO) (PPh3), identified by 1H and 31p NMR studies, were found to be the active forms in the homogeneous system. γ-Al2O3 supported Rh (OH) (CO) (PPh3)2 complex, activated for 2 h in hydrogen atmosphere does not change its catalytic activity for four weeks. X-ray diffraction spectra show that hydrogenation proceeds with participation of rhodium complexes rather than rhodium metal catalytic centers.

Effect of carboxylic acids on the yield and selectivity of the hydroformylation of hex-1-ene catalysed by [Rh(acac) (CO) (PPh3)]

Abstract The effect of the carboxylic acids RCO 2 H (RC 2 H 5 , C 6 H 5 , m -ClC 6 H 4 , p -NO 2 C 6 H 4 and o -HOC 6 H 4 ) on the hydroformylation of hex-1-ene catalysed by Rh(acac) (CO) (PPh 3 ) ( 1 ) have been studied. The decrease of the rate of hydroformylation compared with a carboxylic acid-free system was observed. The inhibiting influence of carboxylic acids is stronger in reactions proceeding in the presence of free phosphine ( e.g. ( 1 )/[RCO 2 H+PPh 3 ]) where not only the reaction rate, but also hex-1-ene conversion decrease. The inhibiting effect of carboxylic acids may be explained by partial elimination of catalytically active forms of the general formula HRh(CO) x (PPh 3 ) y by the reaction of HRh(CO) x (PPh 3 ) y in the presence of RCO 2 H/PPh 3 and H 2 /CO to give Rh(RCO 2 ) (CO) (PPh 3 ) 2 . The equilibrium of this reaction depends mainly on the concentrations of the H + ions and that of free phosphine. Several new rhodium complexes were formed in the reaction of ( 1 ) with RCO 2 H, e.g. , [Rh(RCO 2 ) (CO) (PPh 3 )] 2 , [Rh(RCO 2 ) (CO) 2 (PPh 3 )], [Rh(RCO 2 ) (CO) (PPh 3 ) 2 ], [Rh(RCO 2 ) (CO) 2 ] 2 , have been isolated and used as hydroformylation reaction catalysts. The structures of Rh(acac) (HOC 6 H 4 CO 2 ) 2 (PPh 3 ) (H 2 O) and [Rh(HOC 6 H 4 CO 2 ) (COD)] 2 have been determined by X-ray diffraction studies.

Reactions of Rh(acac)[P(OPh)3]2 with H2, CO and olefins

Abstract The reactions of Rh(acac)[P(OPh)3]2 with H2, CO and olefins have been investigated using UV-VIS, IR, 1H and 31P NMR techniques. In the presence of H2 and free phosphite, Rh(acac)P2 produces HRhP4, which was shown to catalyse isomerization reactions of olefins. Addition of CO to HRhP4 produces HRh(CO)P3, which is a good hydroformylation catalyst. The latter hydride can also be obtained directly from the starting complex in the presence of H2, CO and free phosphite. No evidence for the formation of any hydride complexes could be found in the absence of free phosphite. The results are discussed with reference to earlier studies performed on these systems.

Dehydrogenation of alcohols catalyzed by polystyrene-supported ruthenium complexes

Abstract The dehydrogenation reaction of alcohols catalyzed by Ru(O 2 CCF 3 ) 2 (CO)(PPh 3 ) 2 complex (1) attached to polystyrene, functionalized with phosphine [1-A] and carboxylic [1-B] groups, singly or together [1-C], give as products aldehydes and molecular hydrogen. Comparison of the relative rates for the heterogenized [1-A], [1-B] and [1-C] catalysts and for the ruthenium complex (1) in a homogeneous system indicates a similar reaction mechanism in each case.

The photoinduced metathesis of olefin catalyzed by W(CO)5L-AXn system

Abstract In the photocatalytic system containing tungsten compounds of the type W(CO)5L (L = CO, py, PPh3, Cl−) and Group IIIb and IVab element halides (AXn), the metathesis of internal and terminal olefins was investigated. The terminal olefin metathesis reaction is accompanied by double bond migration yielding the internal olefins, which undergo co-metathesis with the initial olefins. Substitution of tungsten by molybdenum or chromium favours the isomerization reaction.

The molybdenum(V) complexes as the homogeneous and heterogenized catalysts in epoxidation reactions of olefins with the organic hydroperoxides

Abstract The catalytic properties of new Mo(V) complexes with ligands such as ethylene glycol, lactic acid and amygdalic acid in homogeneous systems, as well as the properties of the heterogenized catalysts obtained in the ionic exchange reaction of the complex Na2[Mo2O4(OX)2(H2O)2]·3H2O with Castel A-500p, Dowex 1X8, and Wofatit AD-41 anionites, were examined. The catalysts obtained are active in epoxidation reactions of olefins with organic hydroperoxides. The structure of the heterogenized catalysts is discussed, the catalyst changes during the epoxidation reaction are interpreted, and the correlation between the structure and reactivity of the homogeneous and heterogenized catalysts is considered on the basis of the i.r. spectra.

η3-oxotrimetal hexacarboxylates as heterogenized catalysts in hydroperoxide decomposition and olefin epoxidation reactions

Abstract The catalytic activities of compounds of formula [M 3 O(O 2 CR) 6 (H 2 O) 3 ] n + (M  V, Cr, Mn, Co, Ru, Rh, Mo), attached to a polymer, have been compared in a model epoxidation reaction of cyclohexene. The electronic structure of molybdenum carboxylate has been examined in the solid state, as well as in solution and on a carrier, before and after application in the catalytic reaction. Mechanisms of the hydroperoxide decomposition reaction, and of cyclohexene epoxidation in the presence of the applied catalysts, have been proposed.