Transition Metal Complexes For Olefin Oligomerization And Suzuki/Heck Carbon-carbon Cross Coupling Reaction

This thesis is mainly compromised of two parts: First, several Ni(II) and Cr(III) complexes ligated by amino-salicylaldimine or phosphine ligands were designed and synthesized. Their catalytic activities for ethylene oligomerization were explored under various reaction conditions. Second, a series of Pd(II) complexes bearing various salicylaldimine ligands were prepared and characterized, and also the catalytic activities of these salicylaldimine-palladium complexes toward the Suzuki and Heck reactions were investigated.In the first part, kinds of 5-tert-butyl-3-(R-1-ylmethyl)-salicylaldimine (R =morpholine, piperidine, pyrrolidine, 4-methylpiperazine), diphosphine (P-P, P-O-P, P-S-P, P-N-P) and aminophosphine (P-N-O, P-N-N) ligands were synthesized and structural analyzed. These ligands reacted with CrCl3(THF)3 or NiCl2·6H2O to form Ni(II) and Cr(III) complexes, which were isolated in high yields and characterized by means of IR and elemental analysis. Then these complexes were applied to catalyze ethylene oligomerization under various reaction conditions. To probe the effects of reaction parameters on the ethylene reactivity, oligomerization behavior was typically investigated via changing the amount of MAO/Cr, reaction temperature and reaction time. Under the optimized condition, the Ni(II) and Cr(III) complexes with amino-salicylaldimine ligands show moderate catalytic activities in the range of 2.43×104-2.97×104 g mol-1(Cat.) h-1, while the phosphine chelated Ni(II) and Cr(III) complexes displayed higher catalytic activity and olefin selectivity using less amount of cocatalyst MAO in the same reaction condition. The Ni(II) complex bearing bis(1,2-diphenylphosphino)ethylene ligands exhibited the highest catalytic activity (1.48×105 g mol-1 (Cat.) h-1) and the highest selevtivity for C6 (95.4%).In the second part, a series of salicylaldimine-Pd(II) complexes bearing different amino- , halogeno- or alkyl- substituted salicylaldimine ligands were synthesized and characterized by IR, 1H NMR and elemental analysis. Crystal structure details of two complexes have been confirmed by X-ray structure analysis. The effectiveness of salicylaldimine-Pd(II) complexes were tested in both Suzuki and Heck coupling reactions. In the Suzuki coupling reaction, effects of solvents, bases, reaction temperature and amount of catalysts were first investigated. Under the optimized reaction condition, electronic effect and steric effect of different substituents on the catalytic activities were examined in the model coupling reaction of 4-chlorobenzaldehyde with phenylboronic acid. Then the best catalyst was applied to a representative range of aryl chlorides and was found to be an active catalyst for Suzuki cross-coupling of activated aryl chlorides with phenylboronic acid. In the Heck coupling reaction, the catalytic activity of catalyst was examined in the coupling reaction of aryl bromides with styrene or n-butyl acrylate under the optimized reaction conditions. Catalytic studies showed that the salicylaldimine-Pd(II) complex also exhibited good activities toward activated electron-deficient aryl bromides and exhibited moderate activities toward deactivated electron-rich substrates. Suzuki and Heck reactions were extended to C(sp3)﹣C(sp2) coupling by using halogenated benzyl, which afforded the corresponding coupling product in moderate yields. All these results indicated that electronic effect of substituents on the aryl chlorides had great influence on the reaction and the electron-withdrawing substituents were more favorable for the coupling; also the steric effect of substituents on the olefin could decrease their activities.