Résumé
The reaction of elemental barium with 3,5-di-tert-butylphenol and 18-crown-6 in THF at reflux temperature and/or using gaseous ammonia as catalyst yields a monomeric barium compound. The complex has been characterized by IR,
1H NMR, mass spectroscopy, elemental analysis and single-crystal X-ray studies and shown to be an alcohol and crown-ether solvate: [Ba(OAr)
2(18-crown-6)] · (2ArOH)(18-crown-6). The structure consists of two ArO ligands, one above and one below the planar barium-coordinating polyether resulting in an eight-coordination for the barium atom. The bulky aryloxide anions are hydrogen-bonded to the OH group of the 3,5-di-tert-butylphenol molecule and one free 18-crown-6 molecule fits between two [Ba(OAr)
2(18-crown-6)] · 2ArOH units. The poor thermal stability of this monomeric complex accounts for its non-volatility, whereas its high solubility is attractive for sol-gel processes.