| Hydroformylation is a reaction which converts olefins to aldehydes in the presence of syngas?CO/H2?with 100%atom economy.At present,hydroformylation catalyzed by phosphine ligand modified Rh catalysts is one of the important homogeneous reaction processes in chemical industry.In addition,as the product of hydroformylation,aldehyde is relatively active,which can be further converted into amines through reductive amination,alcohols through hydrogenation,and acetals through acetalization.Therefore,under the same catalytic reaction conditions,the one pot tandem reactions suchas“hydroformylation-reductiveamination”?hydroaminomethylation?,“hydroformylation-acetalization”have attracted wide attentions.In this thesis,the study on Ir-catalyzed?instead of the traditional Rh-catalysts?hydroformylation and tandem hydroformylation?hydroaminomethylation,“hydroformylation-acetalization”?was carried out,wherein the phosphines played important roles in modifying the performance of Ir-catalysts.The main research contents and results are summarized as follows:???Phosphine-modified Ir-catalysts for hydroformylation of olefins with H2O as hydrogen sourceHow to depress hydrogenation of olefins was the key issue in Ir-catalyzed hydroformylation.In this part,water was added instead of H2 to perform Ir-catalyzed hydroformylation,in which H2 was produced in situ via water gas shift reaction?WGSR,H2O+CO?H2+CO2?.Consequently,the side reaction of olefin hydrogenation was completely inhibited.In addition,a series of novel mono-/bi-dentate phosphine ligands with different electronic and steric effects were synthesized.Then the effect of the as-synthesized phosphine ligands on the performance of Ir?I?-catalysts was investigated for hydroformylation with H2O as hydrogen source.It was found that that ionic bi-dentate phosphines of L4 with strong?-accepting ability(1J31P-77Se=781 Hz)could effectively promote Ir-catalyzed WGSR and hydroformylation of olefins.The robustness of L4 with good thermal stability and insensitive to moisture/air made the Ir-catalyst suitable for hydroformylation with H2O as hydrogen source.Resultantly,95%conversion of 1-hexene was obtained with the yields of the target?linear/branched?aldehydes up to 95%as well as<1%yield of hexane.L4-modified Ir?I?-catalytic system also exhibited good generality for hydroformylation with wide range of olefins along with the greatly depressed hydrogenation side reaction.In addition,as a polar and ionic ligand,L4 could be used with the ionic liquid[MePh3P]Br?as solvent?to achieve the recycling uses of the homogeneous catalysts.???Scheme 1 The as-synthesized phosphines and bi-functional ligands???Phosphine-modified Ir-catalysts for tandem hydroformylation?1?Phosphine-modified Ir-catalysts for hydroaminomethylation of olefins?tandem“hydroformylation-reductive amination”?Tandemhydroformylation-reductiveaminationisknownas hydroaminomethylation.This tandem reaction is a three-step process including:1.hydroformylation of olefins;2.condensation of aldehydes with amine;3.hydrogenation of imines.In this part,Ir?I?-catalyzed hydroaminomethylation in syngas?CO/H2?or CO/H2O?H2O as hydrogen source?was studied with involvement of the different phosphines respectively.The results showed that in syngas?CO/H2=5/1?,the mono-phosphines L5 with moderate?-accepting ability?1J31P-77Se=753 Hz?and less steric hindrance could efficiently promote Ir-catalyzed hydroaminoformylation of olefins.The conversion of 1-octene was 98%with 87%yield of the target?linear/branched?amine and 4%yield of octane.L5-modified Ir?I?-catalytic system exhibited good generality for hydroformylation of with wide range of olefins along with the greatly depressed hydrogenation side reaction.The electronic and steric effects of various neutral and ionic?mono-/di-?phosphines on the catalytic performance of Ir-complexes for hydroaminomethylation of olefins were carefully investigated by means of 1J31P-77Se measurement,the single-crystal X-ray diffraction and in situ FTIR spectroscopy.In comparison,hydroaminomethylation with H2O as hydrogen source were investigated over Ir?I?-catalysts modified by the different phosphines.The results showed that when H2O was used as the hydrogen source,the ionic diphosphine of L4with strong?-accepting ability?1J31P-77Se=781 Hz?correspond to the best transformation.The conversion of 1-hexene was 93%with 92%yield of the target?linear/branched?amines as well as<1%yield of hexane.Under the same conditions,when syngas?CO/H2=3/1?was used to replace CO/H2O,only 92%conversion of 1-hexene and 75%yield of target product?straight chain/branched chain?amines could be obtained,along with the yield of the hydrogenated product of 1-hexene up to 18%.It was indicated that H2O as hydrogen source not only avoided the use of the high risky gaseous H2,but also completely inhibited the hydrogenation of olefin.The in situ FT-IR analysis further indicated that the formation and stability of Ir-H species(n2078 cm-1),which was responsible for the key step of hydroformylation in the tandem hydroaminomethylation,was greatly favored over L4-based Ir-catalyst.In addition,as an ionic ligand with high polarity,the L4-based Ir-catalyst could be precipitated by n-hexane upon completion to fulfil the recovery and recycling uses of the homogeneous catalysts.?2?Co-catalysisoverbi-functionalIr-catalystsfortandem hydroformylation-acetalization of olefinsIn this part,the bi-functional Ir-catalysts were constructed by two methods to achieve co-catalytic tandem“hydroformylation-acetalization”.Method 1 was to synthesize the high valance Ir?III?-complexes ligated by the phosphines,which dually served as the phosphine-modified transition metal catalysts?for hydroformylation?and Ir3+metal Lewis acid catalysts?for acetalization?.Method 2 was to synthesize the“phosphino-phosphonium”bi-functional ligands.Then the bi-functional ligand modified Ir?I?-complexes via in situ coordination were applied as the bi-functional Ir?I?-catalysts for tandem“hydroformylation-acetalization”,wherein the phosphino-coordinated Ir?I?-complex acted as the catalyst for hydroformylation and“phosphonium”as a Lewis acid to catalyze acetalization.Firstly,the bi-functional Ir?III?-complexes modified by phosphine ligands was used to catalyze the tandem“hydroformylation-acetalization”of olefin.It was found that,in syngas?CO/H2=5/1?,the tandem“hydroformylation-acetalization”of olefins was efficiently catalyzed by the bi-functional Ir?III?-complex?IrCl3·3H2O as the precursor?modified by L7 with?electron-deficient??-accepting ability.The conversion of 1-hexene was 97%with the selectivity of acetals up to 92%,and the low selectivity of hexane?7%?.The single-crystal structure of the novel IrIII-complex of IrIII-L10showed that the electron-deficient phosphine ligand of L10 could safely coordinate to Ir?III?-center to form a stable hexa-coordinated structure without the redox reaction between the phosphine and the high-valence IrIII-ion,thereby ensuring the Lewis acidity of the Ir?III?-center.Moreover,as an ionic phosphine,L8-based IrCl3×3H2O catalytic system immobilized in the RTIL of[BMIM]PF6 could be recycled for 6 runs without the obvious activity loss or metal leaching.Secondly,the Ir?I?-complex modified by the“phosphino-phosphonium”bi-functional ligand?L11?was used to catalyze the tandem“hydroformylation-acetalization”of olefins.It was found that L11-modified Ir?I?-catalyst?[Ir?COD?Cl]2 as the precursor?could also efficiently accelerate this tandem reaction.The conversion of1-octene was 97%with the selectivity of acetals up to 86%.In addition,as an ionic ligand with high polarity,L11-based Ir?I?-catalyst could be precipitated by n-hexane upon completion to fulfil the recovery and recycling uses of transition metal catalysts.The work in this part indicated that the bi-functional Ir-catalyst system constructed by the two methods mentioned above,could effectively achieve the tandem“hydroformylation-acetalization”of olefins,with additional advantages of the good generality for the olefin substrates and the available recyclability.Moreover,the synergetic co-catalysis over the bi-functional Ir-catalytic systems was more efficient than that of the physical mixtures?Ir?I?-complex+FeCl3?or Ir?I?-complex+phosphonium)of the two individual catalysts. |
PDF Full Text Request