Immobilization of Bis(imino)pyridyliron(II) Complexes on Silica

Abstract

The well-known catalyst precursor 2,6-bis[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine (1) is functionalized by various alkenyl groups to yield the corresponding alkenyl-functionalized 2,6-bis[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine ligand. Reaction of these novel functionalized bis(imino)pyridyl ligands with iron(II) chloride results in the formation of precatalysts 5−7, which possess different spacer moieties. The possibility of self-immobilization has been investigated with respect to the chain length of the alkenyl moiety. Additionally, experiments to heterogenize these functionalized iron(II) complexes on modified silica via hydrosilation are presented (8−10). The immobilization has been studied by IR, and the resulting polymers have been characterized by GPC and static light scattering.

A Flat Model Approach to Tethered Bis(imino)pyridyl Iron Ethylene Polymerization Catalysts

“…[18] XPS confirms that grafting of metal chlorides complexes in gives the corresponding metal complexes in quantitative yield. [16] Ethylene Polymerization Over Supported Bis(imino)pyridyl Iron Complexes Bis(imino)pyridyl iron complex (C) that is supported onto the flat silica model substrate becomes an extremely active ethylene polymerization catalyst when activated with aluminium alkyls.…”

“…[16,17] Briefly the bis (imino)pyridyl ligand with a v-chlorosilane function (complex A) is prepared as described in. [18,19] This ligand reacts with the surface hydroxyl groups of the silica wafer to form a tethered bis(imino)pyridyl ligand (B). Treating these surface ligands with metal chlorides affords the anchored bis(imino)-pyridyl metal complexes (C-E).…”

Iron and Cobalt Complexes of 4‐Alkyl‐2,6‐diiminopyridine Ligands: Synthesis and Ethylene Polymerization Catalysis

“…[14] The concept of selfimmobilization has been extended to other catalytic systems that include late transition metals. [3] Herrmann [15] and Jin [16] functionalized FeCl 2 (pdi) complexes with alkenyl chains at the α-imino or the N-aryl positions, respectively, and they obtained some evidence of the self-immobilization phenomena in spite of the poor capability of iron catalysts for α-olefin incorporation.…”

Iron-Based and Cobalt-Based Olefin Polymerisation Catalysts

“…Herrmann and co-workers reported the immobilisation of bis(imino)pyridine irontype precatalysts on silica. By introduction of an alkenyl group onto the alkyl substituent of the imino carbon of the ligand, [2-{(2,6-i -Pr 2 C 6 H 3 )N=CMe},6-{(2,6-i -Pr 2 C 6 H 3 ) N=C(CH 2 ) n CH=CH 2 }C 5 H 3 N] ( 35 , n = 1-3) [136] , the resultant iron dichloride complex [2-{(2,6-i -Pr 2 C 6 H 3 )N=CMe},6-{(2,6-i -Pr 2 C 6 H 3 )N=C(CH 2 ) n CH=CH 2 }C 5 H 3 N] FeCl 2 ( 36 ) could be readily tethered covalently to give 37 by hydrosilylation ( Scheme 11 ). This family of heterogeneous systems is less active (with MAO) for ethylene polymerisation than its homogeneous analogues; notably the activity increases with tether chain length.…”