Identificador: TDX:843
Autors: Aghmiz, Ali
Resum:
New catalysts for the carbonylation and hydrogenation of alkenes in homogeneous biphasic systemsThe work entitled 'New catalysts for the carbonylation and hydrogenation of alkenes in homogeneous and biphasic systems' consists of three chapters:Chapter I: This chapter studies the hydroformylation and hydrocarboxylation of alkenes in aqueous and perfluorinated biphasic systems. In particular:1) The hydroformylation of vinylarenes in aqueous biphasic systems with rhodium complexes and sulfonated diphosphines. The sulfonated diphosphines used are the achiral diphosphines 1,3-bis [(di-m-sulfonatophenyl)phosphino]propane (dpppts) and 1,4-bis [(di-m-sulfonatophenyl)phosphino]butane (dppbts), and the chiral sulfonated diphosphines (S,S)-2,4-bis [di(m-sulfonatophenyl)phosphino]pentane ((S,S)-BDPPTS) and (R,R)-1,2-bis [di (m-sulfonatophenyl)phosphinomethyl]cyclobutane ((R,R)-CBDTS). In this study it was observed that the activity of the catalytic systems depends on the pH of the medium. In basic medium, these systems are active because [RhH(CO)2(P-P)] species are formed, which are precursors of the active species [RhHCO(P-P)]. In neutral medium, however, these species are not formed, which leads to a drastic decrease in activity.2) The hydroformylation in perfluorinated biphasic systems with rhodium /P(C6H4-p-OCH2C7F15)3 (L1). Those systems are active in the hydroformylation of 1-octene and the results are similar to those obtained with triphenylphosphine in homogeneous systems, which means that the group O-CH2 minimizes the electroattractive effects of the perfluorinated chain on the phosphorus atom of the ligand. The catalytic phase was recycled up to three times with the same activity and selectivity of the system. 3) The hydrocarboxylation of styrene and other vinyl arenes in aqueous biphasic systems with palladium complexes and sulfonated diphosphines (dpppts, dppbts, (S,S)-BDPPTS and (R,R)-CBDTS). These systems are active both in basic and acidic medium. They are, however, much more stable in acidic medium, which makes the catalytic aqueous phases possible to be recycled and the activity, regioselectivity and enantioselectivity in the case of the chiral diphosphines to be maintained.4) The hydrocarboxylation of styrene in aqueous biphasic systems with palladium complexes and the guanidine phosphines tris(3-(N,N-dimethylguanidino)phenyl) phosphine tri-hydrochloride (L2) and 3-guanidinopropyldiphenylphosphine (L3). The system Pd/L3 is more active, while the Pd/L2 system is more stable and more selective in the formation of acids. Chapter II: The chapter studies how rhodium systems and P,N donor ligands derived from DIOP (L4, L5, L6 and L7) can be used in the asymmetric hydroformylation of styrene and other related substrates (figure 1). Figure 1Those systems are active in this reaction however, the enantiomeric excesses obtained are very low because two species are formed ([RhH(CO)2(P-N)] and [RhH(CO)2(P-N)2] in which the ligand acts as a monophosphine) by reaction of Rh and the ligand under H2/CO pressure. Because of the disassociation of a CO molecule, those two species lead to the formation of two active species. Chapter III: This chapter describes the synthesis of chiral bis-(thio)ether ligands (S,S) BDSP(R) (L8 (R = Ph) and L9 (R = iPr)) (figure 2), and the corresponding cationic iridium complexes [Ir((L8) (COD)]BF4 and [Ir((L9) (COD)]BF4. It also describes their application in the hydrogenation of methyl-2- acetamidoacrylate. Figure 2 In this study it has been observed that iridium catalytic systems with bis-(thio)ethers ligands are moderately active in the hydrogenation of methyl-2-acetamido acrylate. The enantiomeric excesses obtained, however, are virtually nonexistent, probably, because the ring formed by the metal and the ligands L8 and L9 is not rigid.
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