ИСТИНА

The so-called Constrained Geometry Complexes (CGCs) since their introduction into the organometallic chemistry in 1991 have been attracted a great deal of attention of research teams around the world. CGCs, once proved to be potent catalysts for olefin polymerization, were extensively investigated during the last several decades. Beyond their application in polymerization reactions, the catalytic activity of CGCs in various other transformations was also tested, and in recent years the number of works in this area increases rapidly. The review part of the dissertation describes the known synthetic approaches to CGCs along with their applications in catalysis. The Result and Discussion section of the present work comprises several parts. The first part reports the development of a synthetic approach to new ligands (5a-f) in which cyclopentadienyl and benzimidazol-2-yl moieties are linked by either a C1 or C2 bridge [-CMe2- (5a), -CHPh- (5b), -CPh2- (5c), -CMe2CH2- (5d), -CHPhCH2- (5e), -CPh2CH2(5f)] starting from available 6-phenyl-, 6,6-diphenyl-, and 6,6-dimethylfulvenes and two lithiated N-CH(OEt)2 protected benzimidazoles [2-methyl substituted (2b) or parent (2a) ones]. While, unfortunately, preparation of 5b and 5c failed due to unavoidable reasons, other ligands of interest could be isolated in moderate or good yields. The known CH-acidity of the methyl group hydrogens in 6,6-dimethylfulvene also presented a noticeable problem and lowered the yields of 5a and 5d. In addition, we unexpectedly observed an N-ethylation of 5f*HCl during its re-crystallization from hot ethanol which afforded the correspondent benzimidazolium salt 5f'' in a high yield. Reaction of compounds 5a, 5e, and 5f with the Group 4 metal tetrakis-amides [(Et2N)4Ti or (Et2N)4Zr] yielded the target CGCs [M = Ti, bridges: -CMe2- (6a), -CHPhCH2- (6b), -CPh2CH2- (6d); M = Zr, bridges: -CHPhCH2- (6c), -CPh2CH2- (6e)]. When examining the reactivity of the mentioned complexes, we, somewhat serendipitously, found out their ability to catalyze the dehydrocoupling reaction between primary or secondary amines and sterically non-hindered primary or secondary silanes. Remarkably, it is the first time when such a feature has ever been observed for CGCs. Complexes 6c, 6e exhibit relatively high activity towards the cross coupling reaction in Et2NH / PhSiH3, t-BuNH2 / PhSiH3 and n-BuNH2 / PhSiH3 systems. Addition of tris(perfluorophenyl)borane (BCF) dramatically promotes this reactions. Meanwhile, complexes 6b and 6d were proved to be inactive under the similar reaction conditions (or demonstrated only negligible activity) even in the presence of BCF. In case of 6e, presence of large excess of t-butylamine in C6D6 caused its transamination which afforded complex 6f. In the Discussion section of the work, possible mechanistic pathways of the dehydrocoupling reaction catalyzed by CGCs are also considered. Besides catalyzing the dehydrocoupling reaction, complex 6e exhibits certain activity in CO2 fixation and olefin polymerization. Its formal 1:1 N-adduct with BCF (6j) is capable to effectively fix C02 that yields an individual crystalline product. Unfortunately, X-ray structural investigation of this material failed due to decomposition of the resulting product. The olefin polymerization activity of 6e activated by either MAO or BCF is rather moderate (1 X 10^3 g*mor1·MPa^-1*h^-1). Attempts to catalyze reactions between acetonitrile or pyridine and phenylsilane with 6e failed. Additionally to the mainstream of the research, a synthetic approach to another type of cyclopentadienyl-type ligands with a pendant imino-group has been explored and two representatives of this family of compounds, namely C5H5-CH=NBu-n (7a) and C5H5-CH=NBu-t (7b) (the latter isolated and characterized in its lithiated form as a 1:1 solvate with THF), were prepared. An interesting cluster-type product of a regulated partial hydrolysis of C5Me5ZrCh (7c) ofhas been also described. Structures of all organic and organometallic compounds under consideration have been adequately confirmed by 1H and 13C{1H} NMR spectroscopy and/or GC-MS method. Crystal and molecular structures of 5f", 6a, 6b, 6c, 6d, 6e, 6f, 6g, 7b, and 7c have been established by X-ray diffraction analysis.