Cationic Titanium Complexes Containing Alkoxide and Carboxylate Pincer Ligands; Noninnocent Role of the Anionic Moieties in Their Reactivity

The reactions of [Cp*TiMe{(OCH2)2py}] (1) and [Cp*TiMe{(OOC)2py}] (2) with triflic acid (HOTf) in the presence of a series of Lewis bases, such as water, pyridine, and tert-butylpyridine, give rise to the corresponding cationic species, namely [Cp*TiL{(OCH2)2py}]+OTf- (3−5) and [Cp*TiL{(OOC)2py}]+OTf- (6, 7). Similar processes with 1 and HOTf in the presence of 2,6-pyridinedimethanol and 2-pyridinemethanol lead to the binuclear complexes [{Cp*Ti((OCH2)2py)}2{μ-(HOCH2)2py}]OTf2 (8) and [Cp*Ti{(OCH2)2py}{(HOCH2)py}]OTf (9), respectively. In an unusual process, the reaction of 3 with NaBPh4 or 1 with B(C6F5)3 yields hydroxo-containing binuclear species, namely [{Cp*Ti((OCH2)2py)}2(μ-OH)][BPh4] (10) and [Cp*Ti(μ-OH){(OCH2)2py}][BMe(C6F5)3] (12), respectively. The X-ray molecular structures of 10 and 12 have been established. Finally, the titanium−aluminum heterometallic complex [Cp*Ti{(OCH2)2py}(μ-O-AlMeOTf)] (16) has been prepared by reaction of 3 with AlMe3.