143063-98-3Relevant academic research and scientific papers
Synthesis and reactivity of [OsH{C6H4(CH=CHH)}(CO)(PPri3) 2] and the formato compounds [Os{(E)-CH=CHPh}(η2-O2CH)-(CO)(PPri 3)2] and [OsH(η2-O2CH)(CO)(PPri3) 2]
Albeniz, Maria J.,Esteruelas, Miguel A.,Lledos, Agusti,Maseras, Feliu,Onate, Enrique,Oro, Luis A.,Sola, Eduardo,Zeier, Bernd
, p. 181 - 192 (2007/10/03)
The complex [OsH{C6H4(CH=CHH)}(CO)(PPri3) 2] has been prepared by reaction of the five-co-ordinate [Os{(E)-CH=CHPh}Cl(CO)(PPri3)2] with LiBun in hexane. It reacts with P(OMe)3 and CO to give [OsH{(E)CH=CHPh}(CO){P(OMe)3}(PPri3) 2] and [OsH{(E)-CH=CHPh}(CO)2(PPri3)2], while under a CO2 atmosphere the formate derivative [Os{(E)-CH=CHPh}(η2-O2CH)(CO)(PPri 3)2] is obtained. Carbonylation of the latter leads to the monodentate formato complex [Os{(E)-CH=CHPh} {η1-OC(O)H}(CO)2(PPri3) 2] and under a hydrogen atmosphere it affords styrene and [OsH(η2-O2CH)(CO)(PPri3) 2], which can be also prepared by reaction of [OsH2(η2-CH2=CHEt)(CO)(PPri 3)2] with CO2. The complex [OsH(η2-O2CH)(CO)(PPri3) 2] reacts with CO, P(OMe)3 and MeO2CC≡CCO2Me to give [OsH{η1-OC(O)H}(CO)L(PPri3)2] [L = CO, P(OMe)3 or MeO2CC≡ CCO2Me]; the carbon atom of its formate ligand is attacked by NEt2H leading to the carbamato compound [OsH(η2-O2CNEt2)(CO)(PPri 3)2] and molecular hydrogen. Similarly treatment of [Os{(E)-CH=CHPh}(η2-O2CH)(CO)(PPri 3)2] with NEt2H afforded [Os{(E)-CH=CHPh}(η2-O2CNEt2)(CO)(PPr i3)2]. The former complex also reacts with HBF4·OEt2, giving two different derivatives depending upon the conditions: in diethyl ether as solvent and in the presence of acetonitrile the vinyl complex [Os{(E)-CH=CHPh}(CO)(MeCN)2(PPri3) 2]BF4 is formed, while the carbene derivative [Os(η2-O2CH)(=CHCH2Ph)(CO)(PPr i3)2]BF4 is obtained in chloroform. The products formed by reaction of [OsH(η2-O2CH)(CO)(PPri3) 2] with HBF4·OEt2 also depend upon the reaction conditions: in diethyl ether and in the presence of MeCN the hydrido compound [OsH(CO)(MeCN)2(PPri3)2]BF 4 is obtained; however a mixture of products, mainly dihydrogen derivatives, is formed in CDCl3. On the basis of theoretical calculations and T1 measurements, the nature and structure of these dihydrogen compounds are discussed.
Hydrogenation of benzylideneacetone catalyzed by OsHCl(CO)(PR3)2 (PR3 = P-i-Pr3, PMe-t-Bu2): New roles of dihydrogen complexes in homogeneous catalytic hydrogenation
Esteruelas, Miguel A.,Oro, Luis A.,Valero, Cristina
, p. 3362 - 3369 (2008/10/08)
The five-coordinated hydrido carbonyl complexes OsHCl(CO)(PR3)2 (PR3 = P-i-Pr3 (1), PMe-t-Bu2 (12)) catalyze the selective hydrogenation of benzylideneacetone to 4-phenylbutan-2-one. In 2-propanol solutions, selectivities close to 100% are achieved. In the presence of 1, the reaction is first-order with respect to the concentrations of catalyst and substrate and independent of the hydrogen pressure. For the reaction catalyzed by 12, the kinetic experimental data are in accordance with an expression of the form -d[benzylideneacetone]/dt = k[12]2[benzylideneacetone](P(H2)). The mechanisms deduced for these reactions, on the basis of the rate laws and spectroscopic observations, illustrate new roles of the dihydrogen complexes in homogeneous catalytic hydrogenation. 1, initially nonactive, is activated as a result of the formation of trans(hydride,dihydrogen)-OsHCl(η2-H2)(CO)(P-i-Pr 3)2 (6), which isomerizes to cis(hydride,dihydrogen)-OsHCl(η2-H2)(CO)(P-i-Pr 3)2 (U) and subsequently dissociates molecular hydrogen. The reaction catalyzed by 12 is proposed to go by the intermediate trans-[OsCl(CO)(PMe-t-Bu2)2]2H4 (18), which could be formed by reaction of 12 with cis(hydride,dihydrogen)-OsHCl(η2-H2)(CO)(PMe-t-Bu 2)2 (20). According to the theoretical works of Burdett and Pourian, this binuclear intermediate could contain a planar 4-gon of cyclically bound hydrogen atoms.
