Crystal and molecular structure of two seven-co-ordinate distorted pentagonal bipyramidal complexes of tantalum(V)

Abstract

Crystals of (I)[TaCl₃L¹₂](L¹=NN′-dicyclohexylacetamidinate) are tetragonal, space group I, with cell dimensions: a= 26.328(9), c= 10.368(5)Å, Z= 8. Crystals of (II)[TaCl₃L¹L²][L²=(probably)NN′-dicyclohexylureate] are monoclinic, space group Cc with cell dimensions a= 12.209(8), b= 23.464(15), c= 12.324(11)Å, β= 115.34(9)°, Z= 4. Both structures were solved by Patterson and Fourier methods from diffractometer data and refined by least-squares methods to R 0.075 [(I), 2 017 reflections] and 0.060 [(II), 2 232 independent reflections]. They are both distorted pentagonal bipyramidal structures with two of the chlorine atoms in axial positions and the other equatorial. The two bidentate ligands complete the pentagonal girdle.