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Synthesis and Characterization of Metal Complexes Derived from a Trisphenolato Phosphine LigandSu, Wei-jia 15 July 2008 (has links)
We utilized the tripodal ligand (tris-(3,5-di-tert-butyl-2-hydroxy-phenyl)- phosphine) H3[O3P] to react with 1 equiv of AlR3 (R = Cl, Me, Et, iBu and OiPr). From NMR and X-ray data proved, we could give the stable Al(III) complexes [O3P-H]AlR (R = Cl, Me, Et and iBu). [O3P-H]AlR is a zwitterionic complexes. Because the phenolato phosphine ligand bond a proton at the phosphorous, and Al(III) coordinated three RO- (tris phenolate group) and one alkyl- substituent group. So the Al(III) metal could be carried -1 charge and the phosphorous could be carried +1 charge. When H3[O3P] reacted with AlR3, the original trisphenolato phosphine ligand ([O3P]3-) was changed into a trisphenoato phosphonium ligand ([O3P-H]2-).
The [O3P-H]AlMe in the trisphenoato phosphonium group has a proton, and we attempted to use a bese to deprotonate the acidic proton. We chose n-BuLi to react with [O3P-H]AlMe, and successfully gave {[O3P:]AlMe}- ionic complexe. In the {[O3P:]AlMe}- complexe, the lone pair electron of phenolato phosphine group is a nucleophile,It reacted with MeOTf of electrophile. The product of the reaction could give [O3P-Me]AlMe.In this reactions, the original trisphenoato phosphonium ligand ([O3P-H]2-) was changed into a new methyl trisphenoato phosphonium ligand ([O3P-Me]2-). We could utilize H3[O3P] to react with 1 equiv MeOTf in diethyl ether, and gave a new tripodal ligand {H3[O3P-Me]}OTf. Also, we utilized the {H3[O3P-Me]}OTf to react with 1 equiv of AlR3 (R = Cl, Me, Et and iBu). We gave that Al(III) complexes [O3P-Me]AlR (R = Cl, Me, Et and iBu).
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Synthesis and study of novel zwitterionic transition metal complexes and their application as olefin polymerisation catalystsMelchionna, Michele January 2007 (has links)
The synthesis, characterization and coordination chemistry of novel zwitterionic late transition metal complexes has been carried out, and an investigation of their ability to act as olefin polymerisation catalysts has been conducted. These systems are based on 6- aminofulvene-2-aldiminate ligands (R2AFA¯) which are capable of binding metal centres via two nitrogen donors, delocalising the negative charge into their cyclopentadienyl moiety, thus resulting in the formation of neutral zwitterionic complexes. Preparation and characterisation of mono- and di-substituted complexes such as Ph2AFACuPPh3, (Ph2AFA)2Zn, (Ph2AFA)2Co, (Ph2AFA)2Ni and (Ph2AFA)2Pd have revealed that this type of ligand has enough flexibility to distort upon coordination to the metal depending on geometrical or steric restrictions. As a result, when the ligand coordination involves narrow binding angle of the metal chelate, as it happens in the square-planar species, a severe loss of planarity of the ligand framework is observed, in contrast with the tetrahedral structures where such binding angles are wider. Although the coordination of the ligand primarily occurs through the nitrogen donors, once they have been occupied by the metal centre, it is possible to exploit the aromatic Cp ring for coordination to a Cp*Ru+ unit. In this way, the synthesis and characterisation of two- and tri-metallic complexes [(Cp*Ru)(Ph’2AFA)Pd(η3-C3H5)][BF4] (where Ph’= 2,4,6-trimethylphenyl) and [(Cp*Ru)2(Ph2AFA)2Pd][BF4]2 has been achieved, featuring the R2AFA¯ molecule acting as an ambidentate ligand, binding the palladium atom in a diimine fashion and the ruthenium centres by means of the C5 ring. The synthesis of the complex Cp*RuPh2AFA where the two N atoms are vacant was also achieved and it was found that this compound acts as a proton sponge in the presence of protic solvents. In an effort to prepare AFA-metal complexes which could be of potential use in olefin polymerisation catalysis, two novel species, [(Ph2AFA)Pd(Me)PPh3] and [(Ph’2AFA)Pd(C3H5)] (where Ph’= 2,4,6-trimethylphenyl) have been synthesised and characterised, and polymerisation tests with ethylene have been carried out. Some preliminary screening of other molecules as monomers for polymerisation catalysis has also been conducted.
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