Reaction of 2,8-Bis(o-hydroxyaryl)quinolines with Group 4 Metal Alkyls Resulting in Three Distinct Coordination Modes of the Tridentate Ligand. X-ray Structure of Complexes and Performance as Precursors in Ethylene Polymerization Catalysis

Abstract

A series of bis(o-hydroxyphenyl)quinolines have been prepared, starting from 2,8-dibromoquinoline. Reaction of these new ligand precursors with group 4 tetrabenzyl complexes MBn 4 results in benzyl substitution of the azine fragment with the formation of amide complexes (M = Ti) or amine complexes with an N−H fragment coordinated to the metal (M = Zr, Hf). The third structural typeZr complexes where the aromatic system of the precursor remains intactcan be prepared through the reaction of the bis(o-hydroxyphenyl)quinolones with 4 mol of methyllithium, followed by ZrCl 4 . The new complexes result in active polymerization catalysts when activated with MAO/borate cocatalysts on silica supports, resulting in polyethylene copolymers with very high molecular weights and multimodal MWDs.

New Alkylidyne Complexes Featuring a Flexible Trianionic ONO3– Pincer-Type Ligand: Inorganic Enamine Effect versus Sterics in Electrophilic Additions

“…Emerging as a class of their own, trianionic pincer ligands, thus far, have been well-suited for stabilizing early transition metals in their high oxidation states. Trianionic [NCN], − [OCO], − [NNN], − [CCC], and [ONO] − ligands are some of the common donor motifs and in combination with the appropriate metal ion will catalyze nitrene and carbene transfer, − ,, aerobic oxidation, ethylene and alkyne polymerization, ,,,, and alkene isomerization …”

“…Emerging as a class of their own, trianionic pincer ligands, 3 thus far, have been well-suited for stabilizing early transition metals in their high oxidation states. Trianionic [NCN], 4−7 [OCO], 8−20 [NNN], 21−25 [CCC], 26 and [ONO] 27−36 ligands are some of the common donor motifs and in combination with the appropriate metal ion will catalyze nitrene and carbene transfer, [21][22][23]27,37 aerobic oxidation, 14 ethylene and alkyne polymerization, 5,6,15,16,36 and alkene isomerization. 5 Important structure−bonding relationships 29,33 within trianionic pincer complexes are emerging and serve to elevate the level of electronic and geometric control over metal ions.…”

Synthesis and Characterization of Group 4 Trianionic ONO3– Pincer-Type Ligand Complexes and a Rare Case of Through-Space 19F–19F Coupling

“…Titanium trianionic pincer complexes are known as well, including the analogous OCO 3− dimeric titanium benzyl complex {[ t Bu(Me)-OCO]TiCH 2 Ph} 2 reported by Golisz and Bercaw 12 and alkyltitanium complexes bearing an unsymmetrical ONO 3− trianionic pincer-type ligand reported by Nifant'ev, Nagy, and co-workers. 10 Hafnium species are poorly represented within this framework, with [2,6-i PrNCN]HfX 2 − (X = Cl, Me) and [3,5-Me-NCN] 2 Hf being the only reported examples. 13 In this work, the ONO 3− trianionic pincer ligand 1 (shown complexed with a metal M in Figure 1) 14 was exploited to synthesize titanium(IV) and hafnium(IV) complexes.…”

Trianionic pincer and pincer-type metal complexes and catalysts

“…Benzyl attack of the pyridine at the 4-position forms the trianionic ONO pincer-type complex 117 (Scheme 55). 139 From the solid state structure of 117, the large ring of the ONO pincer-type ligand is evidently flexible and allows the low-coordinate titanium metal ion to adopt a distorted tetrahedral geometry. The benzyl ligand coordinates Z 2 to maximize electron donation to the unsaturated Ti(IV) ion.…”