טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentNelkenbaum Elza
SubjectNovel Ni(II)-Based Organometallic Complexes:
Synthesis, Structures and Catalytic Activities
DepartmentDepartment of Chemistry
Supervisor Professor Moris Eisen


Abstract

During the past decade, olefin polymerization/oligomerization catalysts promoted by nickel complexes have received increasing interest.

In this work we present the synthesis and structural X-ray diffraction studies on ten new organometallic complexes of nickel(II) containing the chelating benzamidinate ligands. We have chosen the anionic benzamidinate moiety for its exceptional steric and electronic properties that can be readily modified by variation of the substituents in the main framework. In complexes PhC(NSiMe3)2Ni(acac)(TMEDA) (20), p-MePhC(NSiMe3)2Ni(acac)(TMEDA) (25), (PhC(NSiMe3)NC(Ph)=CHSiMe3)Ni(acac)(TMEDA) (31), and [PhC(N-SiMe3)(N'-myrtanyl)]2Ni(Py)2 (33) the ancillary ligands adopt an octahedral environment around the metal, whereas in complexes PhC(NSiMe3)2Ni(acac) (19) and p-MePhC(NSiMe3)2Ni(acac) (24) the metal exhibits a square planar coordination. In complex [p-MePhC(NSiMe3)2]2Ni (26) the metal is coordinated in a tetrahedral geometry; in complex [PhC(NSiMe3)2]2Ni2 (21) the two monovalent nickel metals are arranged in a ''figure-eight'' shape coordination forming a dimer, whereas in complex [p-MePhC(NSiMe3)]2Ni(Py) (30)  the metal adopts a trigonal bipyramidal environment. Complex {[PhC(NH)(N'-myrtanyl)]2Ni}2  (36) shows a ''cross''-like tetrameric structure with two nickel metal centers adopting a square-planar geometry.

            Complexes 19, 31, 33 and 36 activated with MAO have been shown to be efficient catalytic systems for the norbornene vinyl-type polymerization. The catalytic systems 19/MAO, 31/MAO, 36/MAO have been found to oligomerize ethylene to either a mixture of C4 - C6 or/and  C4 - C14 products, depending on the temperature and the solvent used in the reaction. When activated with MAO complex 19 has been found to dimerize propylene to a mixture of hexenes, whereas the use of the catalytic system 33/MAO leads to a mixture of dimers, trimers and tetramers of propylene.