Regioselective formation of [2-(η5-cyclopentadienyl)-2-fluorenylpropane]-titanium complexes: precursors, synthesis, structure and reactivity

Abstract

The 2-cyclopentadienyl-2-fluorenylpropane ligand has been converted into the monometalated derivatives M[CMe2(C5H4)(C13H9)] (M=Li, Tl,) and CMe2[C5H4(SiMe3)](C13H9). These alkylating reagents have been characterized, and used to synthesize a new series of organotitanium (IV) complexes. The trimethylsilyl derivative was treated with TiCl4 to give the monocyclopentadienyl compound [Ti{CMe2(η5-C5H4)(C13H9)}Cl3]. Reaction of the thallium derivative with [Ti(η5-C5R5)Cl3] afforded the ‘mixed-ring’ dicyclopentadienyl complexes [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5R5)Cl2] (R=H, Me), whereas the reaction of TiCl4 with two equivalents of the lithium compound led to the dicyclopentadienyl complex [Ti{CMe2(η5-C5H4)(C13H9)}2Cl2]. The monocyclopentadienyl compound [Ti{CMe2(η5-C5H4)(C13H9)}Cl3] was readily hydrolyzed to give [Ti{CMe2(η5-C5H4)(C13H9)}Cl2]2(μ-O) in wet acetone (0.5% H2O). The dicyclopentadienyl derivative [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5Me5)Cl2] was further converted into [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5Me5)Me2] by alkylation with LiMe. Structural data of the titanium complexes demonstrate the η5-coordination of the cyclopentadienyl ring of the ancillary ligand, whereas the fluorenyl ring is not coordinated to the metal center. This mode of coordination is confirmed by the X-ray crystal structure analysis of [Ti{CMe2(η5-C5H4)(C13H9)}2Cl2].