Collect. Czech. Chem. Commun. 2009, 74, 453-468
Published online 2009-03-06 12:20:17

Intramolecular alkoxide-tethered permethyltitanocene(III) complexes – synthesis and crystal structure

Vojtech Vargaa, Ivana Císařováb, Michal Horáčekc, Jiří Pinkasc, Jiří Kubištac and Karel Machc,*

a Research Institute of Inorganic Chemistry, Revoluční 84, 400 01 Ústí nad Labem, Czech Republic
b Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
c J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic


Singly tucked-in titanocene [Ti(III)(η5-C5Me5)(η51-C5Me4CH2)] (1) reacted readily with di-tert-butyl ketone and 2,4,6-trimethylacetophenone to give permethyltitanocene derivatives [Ti(III)(η5-C5Me5){η5-C5Me4CH2C(t-Bu)2O-κO}] (2) and [(Ti(III)(η5-C5Me5)-{η5-C5Me4CH2CMe(C6H2Me3)O-κO}] (3) with the tetramethylcyclopentadienyl ring tethered to the titanium atom by ethoxy group disubstituted at Cα. Crystal structures of 2 and 3 showed that the Ti–O bond is only slightly inclined to the tethered cyclopentadienyl ligand, and the bulky mesityl or tert-butyl substituents did not impose an observable steric hindrance into molecules of 2 and 3. Whereas the Ti–O bond lengths in 2 and 3 do not significantly differ, a higher wavenumber of the 1a1 → b2 electronic transition for 2 (7326 cm–1) compared with that for 3 (6666 cm–1) indicates a more efficient oxygen-to-titanium π-electron back donation in 2. This is induced by two electron-donating tert-butyl groups on Cα compared with a combined effect of electron-donating methyl and electron-attracting mesityl substituents in 3.

Keywords: Titanium; Permethyltitanocene; Ketones; Di-tert-butyl ketone; 2,4,6-Trimethylacetophenone; Crystal structures; Electronic absorption spectra; Metallocenes; Titanocenes; Sandwich complexes.

References: 31 live references.