Mechanistic Studies on Programmed C―O/C―H Activation with Valence‐Adjusted Ti‐Complexes

Comprehensive Summary Two‐electron reduction of [N 2 NBn]Ti IV Cl 2 ( 3 ) gave a highly reactive [N 2 N]Ti II species, which underwent C—O bond activation of THF (tetrahydrofuran) to generate [N 2 NBn]Ti IV [O(CH 2 ) 4 ] ( 4 ) through oxidative addition. The resulted Ti IV –C sp 3 bond in oxametallacyclohexane was tantamount to the elaborately‐designed Ti‐alkyl complexes, competent to activate intramolecular C sp 2 –H bond, forming ortho ‐cyclometalated complex [N 2 NCH 2 C 6 H 4 ]Ti IV (O n Bu) ( 5 ). Key intermediates were isolated and fully characterized by X‐ray crystallography. Mechanistic studies revealed that the oxidative addition of C—O bond took place at Ti II ‐center via a radical intermediate, while a C sp 2 –H bond activation proceeded by σ‐bond metathesis with a kitelike four‐centered Ti IV ‐transition state.