Antonella Salvini

Alkene isomerization by non-hydridic phosphine substituted ruthenium carbonyl carboxylates

Abstract The behaviour of phosphine substituted ruthenium carbonyl carboxylates in the presence of hex-1-ene has been followed by IR and NMR spectroscopies. The complex Ru4(CO)8(MeCO2)4(PBu3)2 reacts at room temperature with a large excess of hex-1-ene giving the Ru2(CO)4(MeCO2)2(PBu3)(hex-1-ene) compound. The same complex is formed from Ru2(CO)4(MeCO2)2(PBu3)2 and hex-1-ene at 80°C. Mononuclear Ru(CO)2(MeCO2)2(PBu3)2 is not transformed under the same conditions. Catalytic tests performed at 80°C in the presence of Ru4(CO)8(MeCO2)4(PBu3)2 or Ru2(CO)4(MeCO2)2(PBu3)2 indicate that these complexes display almost the same catalytic activity in hex-1-ene isomerization in agreement with the formation of the same intermediate. Working in the presence of Ru4(CO)8(MeCO2)4(PBu3)2 at 80°C, an 85% conversion was obtained after 70 h. The isomeric olefins had a trans/cis ratio of 4.5. A reaction scheme has been suggested to rationalise the behaviour of these complexes.

Ruthenium carbonyl carboxylate complexes with nitrogen-containing ligands III. Catalytic activity in hydrogenation☆

Abstract Several mononuclear and dinuclear ruthenium carbonyl acetate complexes containing bipyridine or phenanthroline have been tested as catalysts in the hydrogenation of alkenes, alkynes and ketones. They are active in polar solvents and in water and the nitrogen-containing ligands are unaltered at the end of the hydrogenation.

New strategies for the synthesis of partially fluorinated acrylic polymers as possible materials for the protection of stone monuments

Abstract The conservation of the cultural heritage requires the development of new materials having specific characteristics that encompass particular attention to durability and efficacy. We approached this problem by synthesizing polyacrylic esters containing variable amounts of fluorine in the α-position of the main chain. These products were obtained from the copolymerisation of ammonium 2-fluoroacrylate and acrylic acid. The polyacrylic acids were esterified using different procedures. The polyester characteristics vary in relation to the polymerisation procedures and degree of esterification. The best esterification results, were obtained using a reaction catalyzed by BF3 or TMSCl. These materials show good properties and are of potential interest for their use as protective agents for stone conservation.

Ruthenium carbonyl carboxylates with nitrogen containing ligands: Part V. On the syntheses and catalytic activity of new ruthenium complexes containing bicarboxylate ligands

Abstract New ruthenium carbonyl carboxylates were synthesised from Ru 3 (CO) 12 and (+)(2 R ,3 R )-tartaric acid or 2,3- O -isopropyliden-(+)(2 R ,3 R )-tartaric acid to improve their solubility in hydroalcoholic solvents. Reactions of these complexes and [Ru 2 (CO) 4 (succ)] n {succ=butan-1,4-dioate} with nitrogen containing ligands, gave Ru 2 (CO) 4 (N–N) 2 (bicarb) complexes {N–N=2,2′-bipyridine, 3,3′-dimethoxy-2,2′-bipyridine, bicarb: (+)(2 R ,3 R )-tartrate or 2,3- O -isopropyliden-(+)(2 R ,3 R )-tartrate, or butan-1,4-dioate}, soluble in hydroalcoholic solvents. These compounds are catalytically active in the homogeneous hydrogenation of CC and CO double bonds in water containing solvents with a high selectivity towards CC double bonds.

Isomerization of olefins by phosphine-substituted ruthenium complexes and influence of an 'additional gas' on the reaction rate

Phosphine-substituted ruthenium carbonyls have often been used as catalytic precursors in reactions such as the hydrogenation or the hydroformylation of olefins. To collect evidence on the coordination of the olefin as a preliminary step of these reactions we have investigated the isomerization of hex-1-ene, in hydrocarbon solvent, in the presence of the phosphine-substituted ruthenium carbonyls Ru(CO)3(PR3)2, Ru3(CO)9(PR3)3 and Ru(CO)2(OAc)2(PR3)2 [R=Bu, Ph]. When using Ru(CO)3(PPh3)2 the rate of the reaction shows a partial first order with respect to the concentration of the catalyst and of the substrate. The activation parameters were also evaluated and the activation entropy is negative. A reaction scheme involving the displacement of a carbonyl ligand with formation of a π-olefin–ruthenium complex is suggested. The rate of the reaction significantly changes if an alcohol is used as solvent. This behaviour is attributed to a modification of the catalytic precursor with formation of a ruthenium hydride. This hypothesis is confirmed by the identification of an alkoxy ruthenium hydride. The isomerization of olefins by phosphine-substituted ruthenium carbonyls is retarded by the presence of an ‘additional gas’ such as dinitrogen. This influence is more evident than the analogous one reported in the hydroformylation reaction: the same pressure of the ‘additional gas’ present in the reaction vessel reduces the rate of the isomerization to a larger extent, i.e. the presence of 1000 bar of nitrogen decreases in otherwise identical experiments the isomerization conversion of hex-1-ene from 95.6% to 25.8%. An analogous effect is also caused by the presence of argon and xenon. Helium, on the other hand, does not display any influence. These data are an indication of an interaction between the ‘additional gas’ and a catalytically active transition metal complex.

Behaviour of triphenylphosphine-substituted ruthenium carbonyl carboxylates with hydrogen

The reaction between Ru(CO) 2 (MeCO 2 ) 2 (PPh 3 ) 2 , or Ru 2 (CO) 4 (MeCO 2 ) 2 (PPh 3 ) 2 , and hydrogen (100 atm) at temperatures between 80 and 160°C has been investigated. The products formed are ruthenium clusters containing PPh 3 , PPh 2 and PPh ligands. The same products were obtained from Ru 4 ( μ -H) 4 (CO) 8 (PPh 3 ) 4 and hydrogen. Several new complexes were isolated and the crystal structures of Ru 3 ( μ -H) 2 (CO) 8 ( μ 3 -PPh)(PPh 3 ), Ru 4 (CO) 8 ( μ 4 -PPh) 2 ( μ -PPh 2 ) 2 and Ru 4 ( μ -H) 4 (CO) 7 ( μ 4 -PPh)( μ -PPh 2 ) 2 (PPh 3 ) are reported.

Reactivity of ruthenium carbonyl carboxylates under hydroformylation conditions

Abstract Ru(CO) 2 (MeCOO) 2 (PBU 3 ) 2 , Ru 2 (CO) 4 (MeCOO) 2 (PBu 3 ) 2 , Ru 4 (CO) 8 (MeCOO) 4 (PBu 3 ) 2 , and [Ru 2 (CO) 4 (MeCOO) 2 ] n react, in the presence of CO, with molecular hydrogen, losing the carboxylato ligand while the metal is reduced to Ru(O). Evidence is given of the involvement of ruthenium hydrides in this reaction. The role of the above precursors in the catalytic cycle of the hydroformylation of olefins is discussed.

The reaction of Ru(CO)2(MeCO2)2(PR3)2 or Ru2(CO)4(MeCO2)2(PR3)2 [RBu, Ph] with H2 in the presence of Na2CO3: a stoichiometric carbon dioxide activation

Abstract The hydrogenolysis of the acetato group by molecular hydrogen in phosphine-substituted ruthenium(I) and (II) carbonyl carboxylates has been reinvestigated in the presence of Na2CO3 at various temperatures. From mononuclear complexes such as Ru(CO)2(MeCO2)2(PR3)2, the intermediate hydrido-acetato complex HRu(CO)2(MeCO2)(PR3)2 has been identified among the products formed working at low temperature. In the case of the binuclear complexes Ru2(CO)4(MeCO2)2(PR3)2 the products obtained at the lowest reaction temperature are H4Ru4(CO)9(PR3)3, H4Ru4(CO)8(PR3)4 and H2Ru(CO)2(PR4)2. The complex H4Ru4(CO)9(PR3)3 is formed from H4Ru4(CO)8(PR3)4 and CO produced from carbon dioxide by the reverse water gas shift reaction catalysed by ruthenium complexes: CO 2 +H 2 ⇄ | Ru | CO+H 2 O Carbon dioxide arises from the reaction between Na2CO4 and acetic acid. Several tests support the involvement of the ruthenium-catalysed reverse water gas shift reaction. At higher temperatures phosphido ruthenium complexes are formed. The same products are obtained in the absence of carbon dioxide.

Ruthenium carbonyl carboxylates with nitrogen containing ligands: IV. Catalytic activity in the hydroformylation of olefins in homogeneous phase☆

Abstract Ruthenium carbonyl acetato complexes containing bipyridines or phenantrolines ligands are tested as catalysts in the hydroformylation of hex-1-ene in homogeneous phase. These catalysts are active also in solutions containing water and the selectivity to aldehyde is high. Only a moderate hydrogenation of the alkene occurs. The regioselectivity to the linear aldehyde reaches 85.7% when using the mononuclear complex containing 4,7-dmphen as ligand. In the course of the reaction the starting olefin is largely isomerized.

The role of functionalized phosphines in the hydrogenation of carboxylic acids in the presence of phosphine substituted hydrido ruthenium complexes

Hydrido ruthenium carbonyl complexes substituted by functionalized phosphines such as H4Ru4(CO)8[P(CH2OCOR)3]4 have been synthesized and tested as catalysts in the hydrogenation of carboxylic acids. These complexes are more active than those reported previously, containing trialkyl- or triarylphosphines. On the basis of their behavior, their different activity has been explained in terms of an involvement of the phosphine ligand in the catalytic cycle. The ester group present in the phosphine P(CH2OCOR)3 is hydrogenated to produce an alcohol (RCH2OH) and a P(CH2OH) group which, in turn, reacts with the free acid present in solution to restore the P(CH2OCOR) group. This hypothesis has been confirmed by the reactivity of the possible intermediate H4Ru4(CO)8[P(CH2OH)3]4 with acetic acid. Another support to this statement is the almost equal catalytic activity, displayed by H4Ru4(CO)8[P(CH2OCOR)3]4 complexes, whatever the R group present, in the phosphine ligand, in the hydrogenation of carboxylic acids. These complexes, on the other hand, are less active than the corresponding tributylphosphine substituted ones in the hydrogenation of alkenes and ketones. Finally when the phosphine ligand is P(CH2CH2COOCH3)3 the ester group is not reduced and consequently the catalytic activity of this complex in the hydrogenation of carboxylic acids is very low.