Synthesis, structures of (aminopyridine)nickel complexes and their use for catalytic ethylene polymerization

Abstract

A series of α-aminopyridines in the form of (2,6-C(6)H(3)N)(R(1))(CHR(2)NR(3)R(4)) (R(1) = R(2) = H R(3) = H R(4) = (i)Pr (L1a), R(4) = (t)Bu (L1b), R(4) = Ph (L1c), R(4) = 2,6-Me(2)C(6)H(3) (L1d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L1e), R(1) = R(2) = H R(3) = R(4) = Et (L1f), R(1) = H R(2) = Me R(3) = H R(4) = (i)Pr (L2a), R(4) = Ph (L2c), R(4) = 2,6-Me(2)C(6)H(3) (L2d), R(4) = 2,6-(i)Pr(2)C(6)H(3) (L2e), R(1) = Me R(2) = H R(3) = H R(4) = 2,6-(i)Pr(2)C(6)H(3) (L3e)) and β-aminopyridines in the form of (2-C(6)H(4)N)(CH(2)CH(2)NR(1)R(2)) (R(1) = H R(2) = (i)Pr (4a), R(2) = (t)Bu (L4b), R(1) = R(2) = Et (L4f)) have been prepared. Their corresponding halonickel complexes 1a-4f are synthesized by ligand substitution from (DME)NiBr(2) and the molecular structures are characterized. Four types of coordination modes include four-coordinate mononuclear species with one ligand, five-coordinate mononuclear species with two ligands, five-coordinate dinuclear species with two ligands, and a six-coordinate polymeric framework were determined by X-ray crystallography. Using methylaluminoxanes (MAO) as the activator, the nickel complexes can catalyze ethylene polymerization under moderate pressure and ambient temperature. The activity reaches 10(5) g PE mol(-1) Ni h. The PE products with high branching and high crystallinity have M(n) ~ 10(3) with PDI < 2.

Structural evolution of iminopyridine support for nickel/palladium catalysts in ethylene (oligo)polymerization

“…This may be the result of the high concentration of ethylene on increasing the solvent volume. 96 The nickel catalysts with 2-benzimidazolylpyridine ( 142 ) or benzoxazolylpyridine ( 143 ) organic supports were preeminently active in the oligomerization of ethylene for C4 and C6 products. Benzoxazolylpyridine gave higher activity than its 2-benzimidazolylpyridine analogue with selectivity up to 99% for C4 and 76% for α-C4.…”

N-[2-(Pyridin-2-yl)ethyl]-derivatives of methane-, benzene- and toluenesulfonamide: prospective ligands for metal coordination

“…Specifically, the two N atoms of contrasting basicities, separated by three C atoms, welcomes a litany of mono-and bidentate ligation to transition and heavy metals. Such diamines are commonly found in metal complexes that catalyze a number of organic transformations (Tai et al, 1986;Nam & Valentine, 1990;Nam et al, 1994;Hirao et al, 1996;Rispens et al, 1996;Lei & Chelamalla, 2013;Scholl et al, 2013), and their complexes have demonstrated promise as anticancer candidates (Dhar et al, 2005;Thyagarajan et al, 2006;Gupta et al, 2008;Zhu et al, 2008;Souza et al, 2009;Xu et al, 2009;Xue et al, 2010;Da Silveira et al, 2011;Panja et al, 2011;Kumar et al, 2012) and polymerization catalysts (Tshuva et al, 2001;Lee et al, 2006;Lin, Yu et al, 2012;Shaikh et al, 2012), and even have potential in fuel cells (Tahsini et al, 2012;Das et al, 2013). Surprisingly, very little is understood regarding the specific medicinal and synthetic potential of N-[2-(pyridin-2-yl)ethyl]-substituted sulfonamides or their corresponding metal complexes, and it is imperative to synthesize a complex library of these molecules in order fully to explore and exploit their potential in these arenas.…”

Bite-Angle-Regulated Coordination Geometries: Tetrahedral and Trigonal Bipyramidal in Ni(II) with Biphenyl-Appended (2-Pyridyl)alkylamine N,N′-Bidentate Ligands

“…A similar example is apparent from careful analysis of a recent report on the Ni(II)-bromide complex of the N-substituted 2- (2-pyridyl)ethylamine bidentate ligand having a hindered diethyl group, which offers a wide bite angle (97°) and stabilizes the four-coordinate tetrahedral geometry. 25 The Ni−N am bond is longer than Ni−N py as expected; this is due to the bulky biphenyl group on the amine nitrogen, which makes N am a weaker σ-donor. The coordination geometry and bond parameters of Ni(II) in 1a−c are comparable to those of related structures.…”

“…The widening of the angle in the present case is due to the combined effect of both the ethyl spacer and sterically hindered biphenyl group. A similar example is apparent from careful analysis of a recent report on the Ni­(II)-bromide complex of the N-substituted 2-(2-pyridyl)­ethylamine bidentate ligand having a hindered diethyl group, which offers a wide bite angle (97°) and stabilizes the four-coordinate tetrahedral geometry …”

“…A similar example is apparent from careful analysis of a recent report on the Ni(II)-bromide complex of the N-substituted 2-(2-pyridyl)ethylamine bidentate ligand having a hindered diethyl group, which offers a wide bite angle (97°) and stabilizes the four-coordinate tetrahedral geometry. 25…”