Titanium(IV) Catecholate‐Grafted Mesoporous Silica KIT‐6: Probing Sequential and Convergent Immobilization Approaches

Molecular Ti IV catecholates were obtained as dimeric complexes from protonolysis reactions of Ti(NMe 2 ) 4 with pyrocatechol (H 2 CAT), 4‐ tert ‐butylcatechol (H 2 CAT t Bu‐4), 3,5‐di‐ tert ‐butylcatechol (H 2 CAT t Bu 2 –3,5), 2,3‐dihydroxynaphthalene (H 2 DHN) and 3,6‐di ‐tert ‐butylcatechol (H 2 CAT t Bu 2 –3,6). The heteroleptic monocatecholate amide complexes were characterized by X‐ray structure analysis but only [Ti(CAT)(NMe 2 ) 2 ] 2 and [Ti(DHN)(NMe 2 ) 2 ] 2 were obtained as pure compounds. The solid‐state structures revealed Ti IV centers bridged by two catecholato ligands adopting a [κ 2 (O,µ‐O′)] coordination mode except for complex [Ti(CAT t Bu 2 –3,6)(NMe 2 ) 2 ] featuring one bridging catecholato and one bridging amido ligand. Heteroleptic complex [Ti(DHN)(NMe 2 ) 2 ] 2 was grafted onto large‐pore periodic mesoporous silica KIT‐6 ( convergent approach ) and the resulting Ti IV surface species compared with the established sequential approach , i.e., grafting of Ti(NMe 2 ) 4 onto the KIT‐6 material and subsequent ligand exchange with H 2 DHN. Dimeric complex [Ti(DHN)(NMe 2 ) 2 ] 2 proved to be sufficiently reactive for a direct grafting yielding the same dominant surface species as obtained according to the sequential approach, as revealed by nitrogen physisorption, elemental analysis, and DRIFT/ 13 C CP MAS spectroscopy.