2-Aminopyrrolines:  New Chiral Amidinate Ligands with a Rigid Well-Defined Molecular Structure and Their Coordination to Ti<sup>IV</sup> Benjamin D. Ward Hélène Risler Katharina Weitershaus Stéphane Bellemin-Laponnaz Hubert Wadepohl Lutz H. Gade 10.1021/ic060809y.s002 https://acs.figshare.com/articles/journal_contribution/2_Aminopyrrolines_New_Chiral_Amidinate_Ligands_with_a_Rigid_Well_Defined_Molecular_Structure_and_Their_Coordination_to_Ti_sup_IV_sup_/3058840 The use of an amino-oxazolinate (NN<sub>ox</sub> = κ<sup>2</sup>-2,6-dimethylphenylamido-4(<i>S</i>)-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(<i>S</i>)-isopropyloxazoline with [Ti(NMe<sub>2</sub>)<sub>4</sub>] afforded the bis(amidinato) complex [Ti(NN<sub>ox</sub>)<sub>2</sub>(NMe<sub>2</sub>)<sub>2</sub>] (<b>2</b>) which was thermally converted to the ring-opened decomposition products [Ti(NN<sub>ox</sub>){κ<sup>3</sup>-N(2,6-C<sub>6</sub>H<sub>3</sub>Me<sub>2</sub>)C(NMe<sub>2</sub>)NC(<sup>i</sup>Pr)CH<sub>2</sub>O}(NMe<sub>2</sub>)] (<b>3</b>) and [Ti{κ<sup>3</sup>-N(2,6-C<sub>6</sub>H<sub>3</sub>Me<sub>2</sub>)C(NMe<sub>2</sub>)-NC(<sup>i</sup>Pr)CH<sub>2</sub>O}<sub>2</sub>] (<b>4</b>). The NMR spectra of <b>4</b> 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 CH<sub>2</sub> group in the synthesis of a series of amino-pyrroline protioligands 2-RN(H)(5-C<sub>4</sub>H<sub>5</sub>NR‘) (HN<sup>R</sup>N<sup>R‘</sup>). Their reaction with [Ti(NMe<sub>2</sub>)<sub>4</sub>] gave the thermally stable complexes [Ti(N<sup>R</sup>N<sup>R‘</sup>)<sub>2</sub>(NMe<sub>2</sub>)<sub>2</sub>], 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 <sup>1</sup>H NMR spectroscopy. 2006-09-18 00:00:00 activation parameters chiral analogue RN ligand rearrangements TiIVThe use NMR spectra amidinate ligands ring opening ONIOM HNRNR undesired side reactions oxygen atom CH 2 group QM