Nickel(II)−Methyl Complexes with Water-Soluble Ligands L [(salicylaldiminato-κ²N,O)NiMe(L)] and Their Catalytic Properties in Disperse Aqueous Systems

Abstract

Neutral (salicylaldiminato)nickel(II) methyl complexes [{6-C(H)dNAr-2,4-I 2 C 6 H 2 O-κ 2 N,O}NiMe(L)] (Ar ) 2,6-{3,5-(F 3 C) 2 C 6 H 3 } 2 C 6 H 3 ) with different water-soluble ligands L (2a, L ) 1,3,5-triaza-7-phosphaadamantane; 2b, L ) hexamethylenetetramine (urotropine); 2c, L ) tetraethylammonium pyridine-3-sulfonate; 2d, L ) amino-terminated poly(ethylene glycol) monomethoxy ether) were prepared. 2a-d are potentially water-soluble catalyst precursors for ethylene polymerization, which form a water-insoluble active site [{κ 2 -N,O}NiR(ethylene)] (R ) growing chain). Only complex 2d was found to be watersoluble (>2 mmol L -1 ); 2c is soluble in water/2-propanol mixtures. In toluene as a reaction medium, only the relatively weakly coordinated tertiary amine complex 2b is polymerization active (1.7 × 10 4 TO). In aqueous systems 2c,d are also active due to compartmentalization of the active site in the polymer particles and of L in the aqueous phase. Polyethylene particle sizes vary from 18 nm (dispersions formed with 2d) to over 0.5 µm (2c) to suspensions (2b) depending on the initial state of the reaction mixture, correlated with catalyst solubility.

Well‐Defined Cationic Methallyl α‐Keto‐β‐Diimine Complexes of Nickel

“…[1] They have been shown to participate in "chain-walking" reactions, [2] exhibit living behavior, [3] incorporate and tolerate polar functionalities, [1,4] and have been used in water. [5] Such flexibility in reactivity is relevant for the development of new materials. [1g, 6] Cationic catalysts and/or initiators are typically generated by electrophilic abstraction reactions from neutral complexes by using coactivators, such as methylaluminoxane (MAO).…”

“…Thermal ellipsoids are drawn at 35 % probability. Selected bond lengths [] and angles [8]: C(2)-N(2) 1.279(6), C(2)-C(3) 1.515 (7), C(1)-N(1) 1.272(6), C(1)-C(3) 1.527 (7), C(3)-O(1) 1.203(6), Ni(1)-N(1) 1.947 (4), Ni(1)-N(2) 1.946 (4), Ni(1)-C(5) 1.995(6); N(1)-C(1)-C(3) 118.6(5), C(1)-C(3)-C(2) 122.4 (5), N(2)-C(2)-C(3) 119.6(5), C(2)-N(2)-Ni(1) 123.0(4), N(1)-Ni(1)-N(2) 96.37 (18), Ni(1)-N(1)-C(1) 123.9 (4).…”

“…Ar = 2,6-diisopropylphenyl, Ar' = 3,5-(CF 3 ) 2 C 6 H 3 . (7), O(1)-Ni(1) 1.904 (5), C(3)-C(1) 1.538 (9), O(1)-Al(1) 1.806 (5), Al(1)-N(1) 1.972(6), N(1)-C(1) 1.278 (7); Ni(1)-N(2)-C(2) 118.1 (5), N(2)-C (2) are well-established, [16] the reaction with TEA and subsequent formation of complex 5 proceeds with the elimination of ethylene, as evidenced by the 1 H NMR spectrum (d = 5.4 ppm in CD 2 Cl 2 at 210 K), probably through direct bhydrogen transfer to the coordinated carbonyl group. [16,17] Comparison of the structural features of 4 and 5 shows that the bulkier ethyl groups in 5 result in a more crowded coordination plane at the nickel center (Figures 2 and 3).…”

Synthesis, characterization and catalytic behaviors of water-soluble phosphine-sulfonato nickel methyl complexes bearing PEG-amine labile ligand

“…The water-soluble catalytic precursors, for example, Ni(II) salicylaldiminato complexes [(N^O)NiMe(L)], could afford nanoparticles with sizes of only ca. 10-30 nm -a size range which is challenging to access by any given polymerization type [14,15]. Such particles can be served as crystalline mesoscopic building blocks for ultrathin films [16][17][18].…”

Well‐Defined Cationic Methallyl α‐Keto‐β‐Diimine Complexes of Nickel

“…[1] They have been shown to participate in "chain-walking" reactions, [2] exhibit living behavior, [3] incorporate and tolerate polar functionalities, [1,4] and have been used in water. [5] Such flexibility in reactivity is relevant for the development of new materials. [1g, 6] Cationic catalysts and/or initiators are typically generated by electrophilic abstraction reactions from neutral complexes by using coactivators, such as methylaluminoxane (MAO).…”