2-Aminopyrrolines: New chiral amidinate ligands with a rigid well-defined molecular structure and their coordination to Ti-IV

Ward, Benjamin David ORCID: https://orcid.org/0000-0003-1406-5940, Risler, H., Weitershaus, K., Bellemin-Laponnaz, S., Wadepohl, H. and Gade, L. H. 2006. 2-Aminopyrrolines: New chiral amidinate ligands with a rigid well-defined molecular structure and their coordination to Ti-IV. Inorganic Chemistry -American Chemical Society- 45 (19) , pp. 7777-7787. 10.1021/ic060809y

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Abstract

The use of an amino-oxazolinate (NNox = κ2-2,6-dimethylphenylamido-4(S)-isopropyloxazoline) as a chiral analogue to amidinate ligands in the chemistry of titanium was found to lead to undesired side reactions. The reaction of 2,6-dimethylphenylamido-4(S)-isopropyloxazoline with [Ti(NMe2)4] afforded the bis(amidinato) complex [Ti(NNox)2(NMe2)2] (2) which was thermally converted to the ring-opened decomposition products [Ti(NNox){κ3-N(2,6-C6H3Me2)C(NMe2)NC(iPr)CH2O}(NMe2)] (3) and [Ti{κ3-N(2,6-C6H3Me2)C(NMe2)-NC(iPr)CH2O}2] (4). The NMR spectra of 4 recorded at low temperature displayed two sets of resonances corresponding to two symmetric isomers in a 2:5 ratio, the probable geometries of which were established by ONIOM (QM/MM) simulations. To suppress ring opening of the oxazolines, their oxygen atom was formally replaced by a CH2 group in the synthesis of a series of amino-pyrroline protioligands 2-RN(H)(5-C4H5NR‘) (HNRNR‘). Their reaction with [Ti(NMe2)4] gave the thermally stable complexes [Ti(NRNR‘)2(NMe2)2], of which three derivatives were characterized by X-ray diffraction. They are stereochemically dynamic and undergo reversible ligand rearrangements in solution, for which the activation parameters were determined by variable-temperature 1H NMR spectroscopy.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	American Chemical Society
ISSN:	0020-1669
Last Modified:	18 Oct 2022 12:24
URI:	https://orca.cardiff.ac.uk/id/eprint/9722

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