Reactivity of C₁‐Symmetric Heteroarylamido Hafnium Complexes towards Unsaturated Electrophilic Molecules: Development of New Families of Olefin Polymerization Catalysts

Abstract

Heteroarylamido hafnium post-metallocenes with [C,N,N]l igands were functionalized by the insertion of small electrophilic unsaturated molecules into the C Ar ÀHf bond of the ligand, which gave rise to various1 ,1-and 1,2-insertion complexes with the modified ligands of previously unknown [] types. It was found that C 1 symmetry of the startingc omplexes, in some cases, results in the formationof two diastereoisomers after 1,1-or 1,2-insertion. Most of the obtained novel complexes were shownt of orm activec atalysts for olefin polymerization in the presence of MAO (methylaluminoxane). Thus, an ew approacht ot he feasible and easy "late stage" modification of the precatalyst structure has been suggested; it can be performed immediatelyp rior to the polymerization tests without isolation and even in ahigh-throughput manner.

Theoretical Elucidation of the Effect of Counteranions on the Olefin Polymerization Activity of (Pyridylamido)Hf(IV) Catalyst by QM and REMD Studies: MeB(C6F5)3– versus B(C6F5)4–

“…This catalyst has recently been utilized in a new polymerization technology, chain shuttling polymerization (CSP), − where ethylene/1-octene multiblock copolymers can be obtained by introducing a chain transfer agent into a solution mixture of two catalyst species with different 1-octene incorporation abilities. Hence, a lot of mechanistic studies − and ligand modifications − of (pyridylamido)­Hf­(IV) catalyst have been conducted so far.…”

Preparation of Pyridylamido Hafnium Complexes for Coordinative Chain Transfer Polymerization

“…In other catalysis [performed with Pd complexes constructed via N-heterocyclic carbene (NHC) ligands], the influence of substituents at the 2,6-position in aryl-N moieties is substantial, and derivatization of the NHC ligand has been carried out by replacing common 2,6-diisopropylphenyl-N parts with 2,6-di(3-pentyl)phenyl-N and 2,6-di(3-heptyl)phenyl-N moieties [30,31]. Much research has also been performed on I [32][33][34][35][36][37][38], and the synthesis of its analogs with the aim to improve the catalytic performance deserves attention [7,29,[39][40][41][42]. Subtle change in the ligand framework sometimes results in dramatic improvement in the polymerization performance and, hence, modification of the substituents has been a main research theme in the development of postmetallocecenes [43][44][45][46][47][48][49].…”

Rigid Postmetallocene Catalysts for Propylene Polymerization: Ligand Design Prevents the Temperature-Dependent Loss of Stereo- and Regioselectivities

“…Accordingly, the 1 H NMR spectrum of 4-Hf in benzene-d 6 was unaffected by the addition of 2 equiv of tetrahydrofuran (THF) or N,N,N′,N′tetramethylurea, a smaller (than THF) probe ligand. 59 In donor-free C 2 -symmetric 2,6-pyridine-bis(3-Ph 3 Si-2naphtholate)HfBn 2 , 57 the openness of the metal atom is witnessed by the large C(Bn)−Hf−C(Bn) angle (110.32°, CCDC 756711), whereas the corresponding Me−Hf−Me angle in 5-Hf is substantially smaller (103.86°) due to the phenylene linkers located near the Hf−Me groups. In this regard, 5-Hf is closer to octahedral "O4"-complexes (Me−Hf− Me angles 97.04−100.21°6 0 ) rather than to pyridine bis(phenolates).…”

“…In the 2,6-pyridine bis (phenolate) complexes, the metal atom is less shielded by the ligand, and thus they are prone to coordination of additional donors. − In contrast, complex 4-Hf does not appear to readily coordinate Lewis bases. Accordingly, the 1 H NMR spectrum of 4-Hf in benzene- d 6 was unaffected by the addition of 2 equiv of tetrahydrofuran (THF) or N , N , N′ , N′ -tetramethylurea, a smaller (than THF) probe ligand . In donor-free C 2 -symmetric 2,6-pyridine- bis (3-Ph 3 Si-2-naphtholate)­HfBn 2 , the openness of the metal atom is witnessed by the large C­(Bn)–Hf–C­(Bn) angle (110.32°, CCDC 756711), whereas the corresponding Me–Hf–Me angle in 5-Hf is substantially smaller (103.86°) due to the phenylene linkers located near the Hf–Me groups.…”