'Tellurium acetylacetonates': crystal structures of 1,1-dichloro-1-telluracyclohexane-3,5-dione and 1-telluracyclohexane-3,5-dione

The crystal structures of the title compounds Cl₂TeC₅H₆O₂, (I) and TeC₅H₆O₂, (II) have been determined by the heavy-atom method and refined by least squares to R 0.060 (I) (1 642 reflections) and 0.058 (II) (1 182 reflections). Crystals of (I) are monoclinic, a = 10.565(7), b = 22.03(1)· c = 7.185(3) Å, β = 130.74(6)°,Z = 6, space group Cm; crystals of (II) are orthorhombic, a = 5.2765(9), b = 10.744(2), c = 22.296(6) Å, Z = 8, space group I2cb. The structures comprise monomeric units. In (I) the tellurium environment is pseudo-trigonal-bi-pyramidal with axial chlorines [means: Te-Cl 2.49 Å: Cl-Te-Cl 171.8° (opposite to the 'lone pair')]; C-Te-C is 95.5°. In (II) C-Te-C is reduced to 89.5°. Te-C in both compounds is 2.16 Å.