Synthesis and structure of dinuclear dimethylene- or 1,4-phenylene-linked bis(decamethyltitanoceneoxide) (TiIII) complexes

The singly tucked-in titanocene [Ti(η5-C5Me5)(η5:η1-C5Me4CH2)] (1) reacts smoothly with ethylene glycol or hydroquinone to give bis(titanoceneoxide) (TiIII) complexes [CH2OTi(η5-C5Me5)2]2 (2) and [(η5-C5Me5)2TiOC6H4OTi(η5-C5Me5)2] (3) containing dimethylene and 1,4-phenylene link, respectively. EPR spectra of 2 in 2-methyltetrahydrofuran glass and 3 in toluene glass revealed that the unpaired d1 electrons are in interaction to form triplet state molecules. The Ti–Ti distance derived from the zero-field splittings D for the two conformations of 2 (7.42 Å and 7.66 Å) are in good agreement with the Ti–Ti distance of 7.2430(7) Å from the X-ray diffraction single-crystal analysis. For 3, however, the Ti–Ti distance derived from D (7.65 Å) is by 1.47 Å shorter than the crystallographic distance of 9.1230(8) Å that indicates an enhancement of the through-space dipole–dipole interaction due to the presence of a conjugated quinonide link.

Triplet state EPR spectra of 2 and 3 in organic glasses afford very similar zero-field splitting D although the crystallographic Ti–Ti distance for 3 is by 1.880(1) Å longer than that of 2. Since a larger bending of 3 in toluene glass is impossible due to steric hindrance, an enhancement of spin interaction by conjugated quinonide link is to be suggested.Figure optionsDownload as PowerPoint slide