CRYSTAL AND MOLECULAR STRUCTURES OF BIS （CYCLOPENTADIENYL） BIS （2,4,6-TRICHLOROPHENOXY）TITANIUM, Cp2Ti（OC6H2Cl3-2,4,6）2 （Ⅰ） AND TETRAKIS（CYCLOPENTADIENYL）BIS （4-CHLOROPHENOXY）-μ-OXO-DIZIRCONIUM,[Cp2Zr（OC6H4Cl-p）]2O （Ⅱ）

The crystal and molecular structures of （Ⅰ） and （Ⅱ） have been determined from single-crystal, X-ray diffraotion data collected by counter methods. Compound （Ⅰ） crystallizes inthe monoclinic space group C 2/c with a=19.618（11） ?, b=9.356（4） ?, c=15.985（8） ?,β=128.84 （3）°, Z=4. The molecule possesses Cpoint symmetry. Compound （Ⅱ） erystallizesin the monoclinic space group P 2/a with a=8.329（2） ?, b=36.509（13） ?, c=10.647（4）?, β=96.04（2）°, Z=4. The oxo-bridge links two [CpZr（OCHCl-p）] units together withthe bond angle Zr-O-Zr of 161.1（9）°. The relatively shorter Zr-O bond lengths show the pre-sence of partial double-bond character. Both Ti and Zr atoms have d° electronic configura-tion in （Ⅰ） and （Ⅱ）. The M-O bonds of the two compounds are discussed.