Synthesis, Characterization, Catalytic Properties Of Lanthanide And Transition Metal Complexes Supported By Pincer Ligands

The catalytic process has irreplaceable importance in modern chemical industry,and the essential is the development of catalysts. An ideal catalyst has to be stable andhighly selective, but also highly active to ensure high turnover numbers and permit lowcatalyst loadings. Moreover, it needs to be amenable to rational design, giving thepossibility for fine-tuning the catalytic properties of the metal center. It is an idealchoice to use pincer complexes, thus the development of new metal complexessupported by pincer Ligands has become a hot field of chemistry research in recentyears.In chapter III, Bis（imino）aryl NCN pincer Fe（II） complexes2,6-（ArN=CH）₂C₆H₃Fe（μ-Cl）₂Li（THF）₂（1a: Ar=2,6-Me₂C6H₃;1b: Ar=2,6-Et₂C₆H₃;1c： Ar=2,6-iPr₂C₆H₃） were synthesized by lithium salt metathesis reactions of theligand lithium salts with FeCl2. X-ray structure analyses of1a and1b revealed that theFe（II） complexes are hetero-dinuclear with the iron atoms in trigonal bipyramidalenvironments. The NCN pincer Co（II） complex{[2,6-（ArN=CH）₂C₆H₃]Co（μ-Cl）}₂Co（μ-Cl）₂（2: Ar=2,6-iPr₂C₆H₃）were synthesized bylithium salt metathesis reactions of the ligand lithium salts with CoCl2. X-ray structureanalyses of2revealed that the Co（II） complexe is trinuclear with the distal Co（II） atomsin2adopt a trigonal bipyramidal geometry with the Cipsoatom of the ligand and twochloride atoms in the equator and the two imine nitrogen atoms in the apical positions.The NCN pincer Ni（II） complexes{[2,6-（ArN=CH）₂C₆H₃]Co（μ-Cl）}（Ar=2,6-iPr₂C₆H₃）Ar=2,6-Et2C₆H₃;3c: Ar=2,6-iPr₂C₆H₃) were prepared via oxidative-addition ofNi（0）（Ph3P）4with bis（N-aryl）-2-bromoisophthalaldimine. These nickel complexes werewell characterized by NMR and elemental analyses. Their solid molecular structureswere established by X-ray diffraction analyses. The nickel metal centers adopt distorted square planar geometries with the bromine atoms as one coordinate ligand. Whenactivated with MAO, the nickel complexes are active for norbornene vinylpolymerization but are inert for butadiene polymerization. The Fe（II） complexes showmoderate activities in butadiene polymerization when activated with alkylaluminumaffording the cis-1,4enriched polymer.In chapter IV, a series of NCO pincer precursors3-（Ar²OCH₂）-2-Br-（Ar¹N=CH）C₆H₃[^Ar1NCO^Ar2]Br （Ar¹=Ar²=2,6-Me₂C₆H₃（6a）; Ar¹=2,6-Me₂C₆H₃, Ar²=2,6-ⁱPr₂C₆H₃（6b）; Ar¹=2,6-ⁱPr₂C₆H₃, Ar²=2,6-Me₂C₆H₃（6c）;Ar¹=Ar²=2,6-ⁱPr₂C₆H₃（6d）） were synthesized and characterized. Reactions of[^Ar1NCO^Ar2]Br withⁿBuLi and subsequent additions of the rare-earth-metal chloridesafford the corresponding rare earth metal pincer complexes ([^Ar1NCO^Ar2]YCl₂（THF）₂（Ar¹=Ar²=2,6-Me₂C₆H₃（7a）, Ar¹=2,6-Me₂C₆H₃Ar²=2,6-ⁱPr₂C₆H₃（7b）, Ar¹=2,6-ⁱPr₂C₆H₃Ar²=2,6-Me₂C₆H₃（7c）, Ar¹=Ar²=2,6-ⁱPr₂C₆H₃（7d））;[^Ar1NCO^Ar2]LuCl₂（THF）₂（Ar¹=Ar²=2,6-Me₂C₆H₃（8a）, Ar¹=Ar²=2,6-ⁱPr₂C₆H₃（8d））;[^Ar1NCO^Ar2]GdCl₂（THF）₂（Ar¹=Ar²=2,6-Me₂C₆H₃（9a）, Ar¹=2,6-Me₂C₆H₃Ar²=2,6-ⁱPr₂C₆H₃（9b）, Ar¹=2,6-iPr₂C₆H₃Ar²=2,6-Me₂C₆H₃（9c）, Ar¹=Ar²=2,6-ⁱPr₂C₆H₃（9d））). All the diamagnetic complexes were characterized by¹H and¹³CNMR spectroscopy and the molecular structure of7a,8a and9a were well establishedby the X-ray diffraction analysis. In7a,8a and9a the metal centers all adopt distortedpentagonal bipyramidal geometries with the NCO donors and two Os of THF in theequator and the two chloride atoms in the apical positions. Activated withalkylaluminium and borate, the gadolinium and yttrium complexes show variedactivities in isoprene polymerization affording high cis-1,4polyisoprene, and the NCOlutetium complexes are inert under the same condition..In chapter V, a series of NCS pincer precursors3-（2,6-Me₂C₆H₃SCH₂）-2-Br-（Ar¹N=CH）C₆H₃[^Ar1NCS^Me]Br （Ar¹=2,6-Me₂C₆H₃（10a）;Ar¹=2,6-ⁱPr₂C₆H₃（10b）） were synthesized and characterized. Reactions of[Ar1NCSMe]Br withnBuLi and subsequent additions of the rare-earth-metal chloridesafford the corresponding rare earth metal pincer complexes({[^Ar1NCS^Me]Y（μ-Cl）}₂（（μ-Cl）Li（THF）₂（μ-Cl））₂（Ar¹=2,6-Me₂C₆H₃（11a）, Ar¹=2,6-ⁱPr₂C₆H₃（11b））;{[^Ar1NCS^Me]Gd（μ-Cl）}₂（（μ-Cl）Li（THF）₂（μ-Cl））₂（Ar¹=2,6-Me₂C₆H₃（12a）, Ar¹=2,6-ⁱPr₂C₆H₃（12b））). All the diamagnetic complexes were characterized by1H and13CNMR spectroscopy and the molecular structure of12a was well established by theX-ray diffraction analysis. Complex12a is a dinuclear with the two equal moietieslinked by two chlorine atoms and two Cl–Li–Cl bridges. In each part, the gadoliniumatom is in the distorted pentagonal bipyramidal geometry. Activated withalkylaluminium and borate, the gadolinium and yttrium complexes show variedactivities in isoprene or butadiene polymerization affording high cis-1,4polymer. In summary, we have systematic study on synthesis, characterization, catalyticProperties of lanthanide and transition Metal Complexes Supported by pincer Ligands.