Acid−Base Adducts of Catalytically Active Titanium(IV) Lewis Acids
- 23 September 1999
- journal article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 38 (21) , 4824-4828
- https://doi.org/10.1021/ic990473a
Abstract
A series of monomeric Lewis acid−base adducts of the Diels−Alder catalyst Ti(O-2,6-Me2C6H3)2Cl2 have been synthesized from bidentate diphosphines and diamines, Ti(O-2,6-Me2C6H3)2Cl2L2 (L2 = dmpe, depe, dpeda, and dmeda). X-ray crystal structures of Ti(O-2,6-Me2C6H3)2Cl2(dmpe) and Ti(O-2,6-Me2C6H3)2Cl2(dpeda) establish a distorted octahedral coordination environment with trans-chloride ligands. Bidentate ligands that were also studied but did not form isolable complexes with the Ti(IV) Lewis acid include dppe, tmeda, and binam. Through pairwise exchange reactions a qualitative ranking of relative bidentate ligand binding strengths to the Lewis acid were obtained (dmeda ≥ dpeda > dmpe ≥ depe > tmeda > binam > dppe). The ranking is readily rationalized using hard−soft electronic arguments except for tmeda, which requires that unfavorable steric interactions be invoked.Keywords
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