1073967-83-5Relevant articles and documents
Alkyloxy- and aryloxy-titanocenes: Synthesis, solid-state structure and cyclic voltammetric studies
K?cher, Stefan,Walfort, Bernhard,Rheinwald, Gerd,Rüffer, Tobias,Lang, Heinrich
, p. 3213 - 3222 (2008)
Alkyloxy- and aryloxy-functionalized titanocenes of type [Ti](Cl)(OR) (R = Me (2), CH2PPh2 (3), CH2Fc (4), C6H5 (5), C6H4-4-C{triple bond, long}N (6), C6H4-4-NO2 (7), C6H4-4-Me (8), C6H4-4-OMe (9), C6H4-4-C(O)Me (10), C6H4-4-CO2Me (11), C6H4-3-NO2 (12); [Ti] = (η5-C5H4SiMe3)2Ti; Fc = (η5-C5H4)(η5-C5H5)Fe) were synthesized by the reaction of [Ti]Cl2 (1) with ROH in a 1:1 molar ratio and in presence of Et2NH. Diaryloxy-titanocenes (e.g., [Ti](OC6H4-4-NO2)2 (13)) are accessible, when the ratio of 1 and ROH is changed to 1:2. This synthesis methodology also allowed the preparation of dinuclear complexes of composition ([Ti](Cl))2(μ-OC6H4O) (14) and ([Ti](Cl)(μ-OC6H4-4))2 (15) by the reaction of 1 with hydroquinone or 1,1′-dihydroxybiphenyl in a 2:1 stoichiometry. Cyclic voltammetric studies show the characteristic [Ti(IV)/Ti(III)] reductions. It was found that the potentials of the alkyloxy titanocenes 2-4 do not differ, while for the aryloxy-titanocenes 5-15 the reduction potentials correlate linearly with the σp/m Hammett substituent constants showing a strong influence of the substituents on the electron density at titanium. The structures of titanocenes 4, 5, 9, and 11-13 in the solid state are reported. Typical for these organometallic sandwich compounds is a distorted tetrahedral coordination geometry around titanium with D1-Ti-D2 angles (D1, D2 = centroids of the cyclopentadienyl ligands) of ca. 130 °. In comparison to FcCH2O-functionalized 4, for the aryloxy-titanocenes 5, 9, and 11-13 a significant larger Ti-O-C angle was found confirming electronic interactions between the titanium atom and the appropriate aryl group.
