792934-67-9Relevant academic research and scientific papers
Chiral complexes of a new diazaallyl ligand: Group 4 aminooxazolinates
Westmoreland, Ian,Munslow, Ian J.,Clarke, Adam J.,Clarkson, Guy,Scott, Peter
, p. 5066 - 5074 (2008/10/09)
A new biaryl-bridged bis(iminooxazolidine) proligand H2L is prepared in good yield from 2,2-diamino-6,6′-dimethylbiphenyl. The direct reaction of H2L with [Ti(CH2Ph)4] leads via deprotonation of the ligand to the C2-symmetric dibenzyl complex [LTi(CH2Ph)2] (85%) containing diazaallyl ligation. The analogous group 4 complexes [LZr(CH2Ph)2] (79%) and [LHf(CH2Ph)2] (91%) are similarly obtained. Molecular structures of these three compounds indicate C2-symmetry in all cases and that the chirality of the backbone is well expressed in the coordination sphere. Reaction of H2L with Ti(NMe2)4 gives the amide [LTi(NMe2)2] (90%), which on reaction with SiMe3Cl gives the chloride [LTiCl2] (78%). The dichloride [LZr-(NMe2H)Cl2] is prepared via treatment of H 2L with Zr(NMe2)2Cl2(THF) 2 (86%). The direct reaction of H2L with TiCl 4(THF)2 gives the adduct [(H2L)TiCl 4] (83%), which is shown by X-ray crystallography to contain intramolecular NH...C1 hydrogen bond contacts. The complexes were tested as precatalysts for the polymerization of ethene and 1-hexene using a range of cocatalysts and were found to display low activity. Correspondingly, NMR studies on a presumed active species [LZr(CH2Ph)] [B(C6F 3)3(CH2Ph)] were consistent with tight ion pairing on the NMR chemical shift time scale.
