Titanium imido complexes utilizing orthometallated derivatized acetophenone and piperonal imine ligands: synthesis, isolation, and characterization

Abstract

A series of five ortho-lithiated imines (Li-L(n); n = 1-5) was synthesized via the reaction of an aryl or alkyl acetophenone imine with n-butyllithium. The ortho-lithiated imines were subsequently reacted with Ti(NR)Cl(2)py(3) (R = C(CH(3))(3), 2,6-Me(2)C(6)H(3), 2,6-Et(2)C(6)H(3), or 2,6-(i)Pr(2)C(6)H(3)), yielding complexes of the form (L(n))(2)Ti(NR). Several of the resulting complexes [(L(1))(2)Ti(NC(CH(3))(3)), 1a; (L(3))(2)Ti(N-2,6-Me(2)C(6)H(3)), 3b; and (L(5))(2)Ti(NC(CH(3))(3)), 5a] were structurally characterized using small molecule X-ray diffraction. The C(2) symmetric complexes produced in these reactions displayed a distorted square pyramidal geometry. In each complex the titanium center was located above the square plane of the two coordinated bidentate ligands and the chelating C approximately N ligands were folded away from the metal center. When a less sterically demanding alkylimine was used (L(4)), the resulting complex was isolated as an equilibrium mixture of cis and trans isomers of the empirical formula (L(4))(2)Ti(NC(CH(3))(3))py (cis/trans 4a).

Main Group Metal‐Mediated Transformations of Imines

“…Utilizing the potential of this non‐conventional directing group, Schmidt and co‐workers have published several studies [36–39] on the directed ortho ‐lithiation of a wide variety of 3,4‐methylenedioxyphenyl imines. Selective lithiation in all cases is achieved using commercial n BuLi in pentane at −78 °C or 0 °C (Scheme 5).…”

“…Utilizingt he potential of this non-conventionald irecting group, Schmidt and co-workersh ave published several studies [36][37][38][39] on the directed ortho-lithiationo fawide variety of 3,4methylenedioxyphenyl imines.S elective lithiation in all cases is achieved using commercial nBuLi in pentane at À78 8Co r08C (Scheme5). These anionic units are used as ancillary ligands, via metathesis reactions, to afford aw ide variety of metal complexes including Mg, [38] Zn, [38,40] Al, [38] Cu I , [38] Ti, [37,39] Zr, [39] Nb, [36] Ta , [36] and Sn IV . [38] Al arge number of these metal complexes have been successfully characterisedi nt he solid state highlighting the importance of the imine nitrogen atom providing extra stabilityt hrough chelation to the metal centre.…”

Titanium, zirconium, hafnium

“…71 A tetradentate [OSSO]-type diphenolate ligand with a trans-1,2-cyclooctanediylbis(thio) core forms a six coordinate zirconium dibenzyl complex which on activation is a very good catalyst for the polymerization of 1-hexene to highly isotactic poly(1-hexene). 72 78 The arylimides [Ti(Z 5…”

Structural Characterization of Novel ortho‐Lithiated Imines

“…[23,24] To date, we have investigated the use of these anionic units as ancillary ligands in compounds of titanium, zirconium, niobium, and tantalum. [23][24][25] Due to the interesting NMR spectroscopic features observed for these ortho-lithiated imines and the general lack of structurally characterized examples of this class of molecules, we embarked on a study of the molecular structure of these ortho-lithiated imines, crystallized from a wide variety of nonpolar solvents. In this contribution, we show the results of the crystallization of these species from both coordinating and noncoordinating solvents, the impact of steric bulk of the imine substituent, and the overall clustering observed in a series of eight ortholithiated imines.…”