Collect. Czech. Chem. Commun. 2008, 73, 1161-1176

Synthesis and Structure of Permethylcyclopentadienyltitanium Diisopropoxide Zwitterionic Complex

Vojtech Vargaa, Jiří Pinkasb, Ivana Císařovác, Róbert Gyepesc, Karel Machb, Jiří Kubištab and Michal Horáčekb,*

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


Half-sandwich pentamethylcyclopentadienyltitanium chloroisopropoxides [Ti(η5-C5Me5)-Ti(Oi-Pr)nCl3-n] (n = 1 (1) or 2 (2)) and methylisopropoxides [Ti(η5-C5Me5)Ti(Oi-Pr)nMe3-n] (n = 1 (3) or 2 (4)) were prepared and characterized by spectroscopic methods, and compound 1 by single crystal X-ray diffraction analysis. Compounds 3 and 4 were reacted with an equimolar quantity of B(C6F5)3, however, only compound 4 afforded a crystalline product of limited stability at ambient temperature. Its single crystal X-ray diffraction analysis revealed that it is the zwitterionic complex [(η5-C5Me5)Ti(Oi-Pr)2]+[(μ-Me)B(C6F5)3]- (5) and its crystal structure is very similar to the recently reported tert-butoxy complex [(η5-C5Me5)-Ti(Ot-Bu)2]+[(μ-Me)B(C6F5)3]- (6). The 1H, 13C, and 19F NMR spectra in C6D6 solution also showed the features analogous to those of 6. 1D NOESY experiments proved a close through space interaction of irradiated C5Me5 or OCHMe2 protons with the bridging Ti···Me-B group. The NMR data indicate the inner sphere ion pair structure of 5 in C6D6, like for 6. The crystal structure geometry of the C-H bonds of the Ti···Me-B group fulfils conditions for their agostic interaction with the titanium centre. Although structurally similar to 6, compound 5 is less thermally stable apparently due to a lower bulkiness of Oi-Pr group compared to that of Ot-Bu group.

Keywords: Titanium; Half-sandwich; Titanium isopropoxide; Tris(pentafluorophenyl)borane; Zwitterionic complex; Cationic titanium complex; NMR spectra; Crystal structure.

References: 40 live references.