Synthesis and structures of paramagnetic binuclear (η 8-1,4-bis(trimethylsilyl)cyclooctatetraenide)titanium(III) chlorides

Abstract

The reaction between equimolar quantities of TiCl 3(THF) 3 and 1,4-bis(trimethylsilyl)cyclooctatetraene dianion (COT″) yields a mixture of (COT″) 2Ti ( 1), [(COT″)Ti] 2(μ-Cl) 3 ( 2) and [(COT″)Ti(μ-Cl)] 2(THF) ( 3). Crystalline 2 and 3 were isolated on the basis of different solubility in hexane. Their X-ray diffraction analyses revealed dimeric structures linked by chlorine bridges. In 3, only one of the Ti atoms coordinates one molecule of THF. The mixed-valency Ti(III)/Ti(IV) compound 2 shows an ESR spectrum typical of mononuclear (COT″)Ti(III) complexes. The ESR spectra of 3 in toluene or 2-methyltetrahydrofuran glasses prove the triplet state of coupled Ti(III) d 1 electrons.