Synthesis And Appliction Of Palladium Complex-Functionalized Ionic Liquids In (Carbonylative) Coupling Reaction

Ionic liquids (ILs) are featured with many unique properties including non-detectable volatility, good solubility as high polar compounds, good thermal stabilities, as well as the flexible modification by the functional groups. Specifically, the functionalization of ILs has become one of the important methods for heterogenization of homogeneous catalysts, such as transition metal complexes, in combination with the uses of room temperature ILs as the solvents.In this thesis, a series of novel Pd(II)-complex functionalized ILs (FILs) have been synthesized successfully and applied as the pre-catalysts in the (carbonylative) coupling reactions.In the first part of this thesis, a series of phosphine-FILs were synthesized (Scheme1,1-9), including monodentate phosphine-FILs (1-3) and bidentate phosphine-FILs (4-9). The corresponding novel Pd(II)-complex-FILs of11-15, which were ligated by1-5respectively (Scheme1), were synthesized and fully characterized by1H/31P NMR, FT-IR, TG/DTG, CHN-elemental analysis and single crystal X-ray diffraction. As for the phosphine-FILs of1-9, in which the phosphorpus atoms were neighbored to the positive-charged imidazolium or benzoimidazolium rings at the2C positions, the coordination behaviors of them differed from the neutral tertiary phosphines with the typical σ-electron donating character. These phosphine-FILs were featured with both σ-electron donating ability and π-electron accepting ability, which can increase the stability of the corresponding Pd complex-FILs due to the π-back bonding from the Pd ion to the phosphorus fragment. In addition, the intensive electron withdrawing ability of the positive-charged imidazolium or benzoimidazolium rings can decrease the electron density of the vicinal phosphorous, which corresponds to the insensitivity to moisture and oxygen for these phosphine-FILs and the corresponding Pd-complexes FILs.Firstly, the obtained Pd(II)-complex FILs of11-14ligated by the phosphine-FILs of1,2,4, and5respectively along with the same counteranion of OTf were selected as the pre-catalysts for carbonylative Sonogashira couplings of ary halides and phenylacetylene. Under the mild conditions (CO pressure0.5Mpa,0.05mol%Pd cat.100℃and1.5h),11-13all exhibited the competitive activities in the room temperature IL of [BPy]BF4towards the carbonylative Sonogashira couplings of ary halides and phenylacetylene, in comparison to that of trans-Pd(PPh3)2Cl2. Whereas14which was chelated by a phosphine-carbon anion-carbene (PCC) pincer, exhibited poor activity due to the high stability and then the difficult formation of the active Pd (0) species. The recycling experiments showed that13could be recycled for5runs in [Bpy]BF4without the obvious activity loss or the detectable metal leaching. The generality of13as the pre-catalyst for this reaction indicated that aryl iodides with electron-donating converted excellently with high selectivity to the desired carbonyl compounds; whereas the aryl iodides with the electron-withdrawing groups proved to yield the competitive Sonogashira coupling products. No discrimination for the steric effect of the substituents on the substrate conversion was observed. Aryl bromide could not be activated under the CO atmosphere. A reasonable catalytic mechanism for this reaction was proposed herein.Secondly, the Pd(II)-complex-FIL of15with the hydrophobic counter anion of PF6-was selected as the pre-catalyst for Sonogashira couplings of aryl iodides/bromides and terminal acetylenes, along with the hydrophobic room temperature IL of [Bmim]PF6as a solvent. It was found that under the aerobic and Cul-free conditions,15proved to be a highly efficient catalyst for this reaction, which could be reused in [Bmim]PF6for7runs without the detectable Pd leaching or the activity loss. The accumulated ammonium salt generated in the reaction could be removed easily out of the hydrophobic IL phase by water to refresh15and [Bmim]PF6.In the second part of this thesis, ionic Pd-complex16was synthesized based on ionic ligand of meso-tetra(p-sodium sulfonate)porphyrin10. Then SBA-15-immobilized Pd-porphyrin-FIL was obtained as supported ionic liquid catalyst (SILC) for the Heck reaction of aryl halides and ethyl acrylate, in which the catalyst could be easily recovered and recycled. The characterization of catalyst by means of PXRD, FT-IR, UV-visible, ICP, N2sorption analysis, and TEM proved that the SBA-15supported Pd-porphyrin-FIL could be could be recovered and recycled9times without SBA-15structural collapse, Pd species leaching and obvious activity loss.