Preparation, Structure, and Olefin Polymerization Behavior of Functionalized Nickel(II) N-Heterocyclic Carbene Complexes

Abstract

Picolyl-functionalized N-heterocyclic carbene complexes have been synthesized by a route involving carbene transfer from Ag(I) carbene precursors. The Ag complexes undergo facile reaction with Ni(PPh 3 ) 2 Cl 2 to yield the carbene complexes Ni(C∧N) 2 Cl 2 (C∧N ) 3-methyl-1-picolylimidazolin-2-ylidene (2a), 3-benzyl-1-picolylimidazolin-2-ylidene (2b)). Complexes 2a,b have been characterized by IR and 1 H and 13 C NMR spectra and elemental analyses. The molecular structures of complexes 2a,b have been confirmed by X-ray single-crystal analyses. The carbene complex 2a shows high catalytic activities of up to 2.6 × 10 7 g of PNB (mol of Ni) -1 h -1 for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst and exhibits moderate catalytic activity (3.3 × 10 5 g of PE (mol of Ni) -1 h -1 ) for ethylene polymerization. Catalytic activities, polymer yield, molecular weights, and molecular weight distributions of polynorbornene have been investigated under the various reaction conditions.

Preparation and Structure of Mono‐ and Binuclear Half‐Sandwich Iridium, Ruthenium, and Rhodium Carbene Complexes Containing 1,2‐Dichalcogenolao 1,2‐Dicarba‐closo‐Dodecaboranes

“…In the 13 C NMR spectra the signals for the carbene carbon of complexes 2, 3, 6-8 appear at d 156.4 (2), 173.7 (3), 171.8 (6), 171.6 (7), 176.4 ppm (8), respectively, which is characteristic for a metal-carbene signal.…”

“…The equivalency of the imidazolyl rings confirms the two-fold symmetry of the ligand. Compounds 10 and 11 could hardly be re-dissolved in organic solvents after they precipitated, so that we couldnt obtain solutions concentrated enough for 13 C NMR spectrum.…”

“…Recently, we have reported the facile synthesis of pyridine-functionalized carbene or carborane transitionmetal complexes and investigated their application in olefin polymerization. [13] In order to understand the chemistry of transition-metal complexes containing both NHC and carborane ligands, herein we report an easy way to synthesis mononuclear and dinuclear transition metal N-heterocyclic carbene complexes from 16-electron "pseudo-aromatic" complexes [LMA C H T U N G T R E N N U N G {E 2 C 2 A C H T U N G T R E N N U N G (B 10 H 10 )}] (L = Cp*, p-cymene; M = Rh, Ir, Ru).…”

Nickel N‐heterocyclic carbene complexes in the vinyl polymerization of norbornene

“…The IR spectra of the polymer products are consistent with the spectrum reported for vinyl-polymerized norbornene. [20] Peaks indicative of double bonds (1680-1620 cm −1 ) are not observed, indicating that the product was not obtained via ROMP. [19] The 1 H and 13 C NMR spectra are very similar to those reported and also show no resonances assignable to double bonds.…”

“…[19] To the best of our knowledge, the use of nickel N-heterocyclic carbene complexes in this reaction has only been reported twice. These concern a complex with two picolyl-functionalized N-heterocyclic carbene (NHC) ligands, [20] and a nickel compound bearing one bulky monodentate NHC and one η 3 -coordinated benzyl moiety. [21] N-heterocyclic carbenes are increasingly used in homogeneous catalysis as stable, versatile spectator ligands.…”