2-tert-Butyl and 2-phenylphenylimido complexes of titanium(IV) and their olefin polymerisation activity

Abstract

Reaction of 7 equivalents of tert-butylamine with TiCl 4 in hexane at 0 ЊC gave [TiCl 2 (NCMe 3 )(NH 2 CMe 3 ) 2 ] 2 1 which on thermalisation with 2,6-diisopropylaniline in toluene gave [TiCl 2 (NC 6 H 3 Pr i 2 -2,6)(NH 2 CMe 3 ) 2 ] x 2. Imido exchange of [TiCl 2 (NCMe 3 )(NH 2 CMe 3 )] x with o-toluidine or 2-tert-butylaniline and addition of pyridine gave [TiCl 2 (NC 6 H 4 -Me-2)(py) 3 ] and [TiCl 2 (NC 6 H 4 CMe 3 -2)(py) 3 ] which crystallised to give [TiCl 2 (NC 6 H 4 Me-2)(py) 2 ] 2 3 and [TiCl 2 -(NC 6 H 4 CMe 3 -2)(py) 2 ] 2 4. 2-Phenylaniline and [TiCl 2 (NCMe 3 )(py) 3 ] gave [TiCl 2 (NC 6 H 4 Ph-2)(py) 2 ] 2 5 on crystallisation and reaction of tert-butylaniline or 2-phenylaniline with [TiCl 2 (NCMe 3 )(tmeda)] gave [TiCl 2 (NC 6 H 4 CMe 3 -2)(tmeda)] 6 and [TiCl 2 (NC 6 H 4 Ph-2)(tmeda)] 2 7. Complexes 1, 3, 4, 5, 6, and 7 were characterised by X-ray crystallography and the possibility of imdo ligand C-N bond rotation taking place analysed and compared with the NMR spectra. [TiCl 2 -(NCMe 3 )(tmeda)] and MAOؒ(MeAlO) n , polymerises ethylene at low pressure with low activity (3.2 g mmol Ϫ1 h Ϫ1 bar Ϫ1 ), [TiCl 2 (NC 6 H 4 CMe 3 )(tmeda)] or [TiCl 2 (NC 6 H 4 Ph-2)(tmeda)] and MAO gives a 4-fold increase in activity whereas propene is not polymerised but 1-hexene is. Heterogenisation by addition of [TiCl 2 (NCMe 3 )(NH 2 CMe 3 ) 2 ] 2 1 to tmeda-functionalised crosslinked polystyrene or imido exchange of [TiCl 2 (NCMe 3 )(tmeda)] with NH 2functionalised crosslinked polystyrene gives supported complexes which do not polymerise ethylene at low pressure in the presence of MAO.

Titanium Imido Complexes of Cyclooctatetraenyl Ligands

“…[30] Results and Discussion Synthesis and characterisation of cyclooctatetraenyl titanium imido complexes: Titanium imido dichloride starting materials [Ti(NR)Cl 2 (py) 3 ] (R= tBu, 2,6-Me 2 C 6 H 3 , 2,6-iPr 2 C 6 H 3 and 2-tBuC 6 H 4 ) were prepared according to previously described routes. [21,26] Reaction of these with either K 2 [COT] (COT = C 8 H 8 ) or the more sterically bulky Li 2 -[COT'']·1.8 THF (COT'' = 1,4-bis(trimethylsilyl)-1,3,5,7-cyclooctatetraenyl) gave products that depended critically on the exact nature of both the imido and cyclooctatetraenyl ring substituents. Addition of one equivalent of either K 2 [COT] or Li 2 [COT'']·1.8 THF to [Ti(NtBu)Cl 2 (py) 3 ] in THF at À50 8C gave a dark red solution.…”

“…[1][2][3][4][5][6][7] Both computational and experimental studies have been performed to probe the structure and reactivity of these systems. It has been shown that Group 4 transition-metal imides have potential in CÀH activation chemistry, [8][9][10][11][12][13][14][15][16] materials chemistry [17][18][19][20] and olefin polymerisation catalysis (with the imide acting as an "ancillary ligand"), [21][22][23] and that these systems can be utilised in an wide variety of stoichiometric and sometimes catalytic coupling reactions with unsaturated substrates. [6] Terminal titanium imido complexes were first structurally characterised in 1990, [24,25] and since then a large number of imido complexes with different ancillary ligands have been synthesised.…”

“…Literature preparations: [Ti(NtBu)Cl 2 (py) 3 ], [26] [Ti(N-2,6-Me 2 C 6 H 3 )Cl 2 -(py) 3 ], [26] [Ti(N-2,6-iPr 2 C 6 H 3 )Cl 2 (py) 3 ], [26] [Ti(N-2-tBuC 6 H 4 )Cl 2 (py) 3 ], [21] K 2 [COT], [59] and Li 2 [COT'']·1.8 THF [60] were prepared by using literature methods.…”

Transition Metal Imido Compounds as Ziegler–Natta Olefin Polymerisation Catalysts

“…Heterogenisations were also attempted by using asc.wiley-vch.de modified polystyrene resins containing TMEDA groups. [58] However, preliminary results showed that these compounds were inactive [in contrast to the situation for the supported vanadium(V) catalysts of Gibson et al discussed below].…”

“…Some closely related work was reported by Nielson et al in which the triazacyclononane ligand is replaced by a TMEDA (tetramethylethylenediamine) ligand. [58] Since the TMEDA ligand only possesses two nitrogen donors the resulting compounds possess 14 valence electrons in contrast to the 16 valence electron complexes discussed above. In addition to the compound with a tert-butyl imido group (12), two further compounds were synthesised, each having arylimido groups with bulky ortho substituents.…”