THE CRYSTAL AND MOLECULAR-STRUCTURE OF [(C5HME4)TIBR(MU-O)]4 AND [(C5ME5)TIBR(MU-O)]3, BY-PRODUCTS FROM THE PREPARATION OF TITANOCENE DIBROMIDES

The compounds [(C5HMe4)TiBr(mu-O]4 (I) and [(C5Me5)TiBr(mu-O)]3 (II) result from hydrolysis of (C5HMe4)TiBr3 and (C5Me5)TiBr3, respectively, in THF with aqueous HBr. They appear as byproducts if during the preparation of the corresponding titanocene dibromides air is accidentally introduced, or if substoichiometric amounts of reducing agents are present prior to addition of aqueous HBr. Such conditions cause formation of the cyclopentadienyltitanium dibromides or tribromides. The molecule of I forms a planar eight-membered titanoxane cycle with a two-fold symmetry axis perpendicular to the plane of the cycle. The Ti-O-Ti angles are alternately 149 and 176-degrees whereas the O-Ti-O angles are nearly constant at 103-106-degrees. The six-membered titanoxane cycle in II is planar except for the oxygen atom which connects the titanium atoms bearing those C5Me5 ligands oriented on the same side with respect to the plane; displacement of the oxygen atom is 0.4 angstrom.