No abstract

No abstract

No abstract

The crystal and molecular structure of tetraphenylarsonium tris(benzenedithiolato)tantalate(V), [(CsHs^As] [Ta(S2C6Ü4)3], has been determined from three-dimensional X-ray diffraction methods using data collected with an automated diffractometer.The compound crystallizes in the triclinic space group P\ (No. 1) with one molecule per unit cell of dimensions a = 9.442 (1), b = 9.752 (1), c = 11.872 (2) A and a = 77.37 (1), ß = 71.20 (1), y = 74.23 (1)°. The observed and calculated densities are 1.67 (2) and 1.66 g cm™3, respectively. A total of 3700 reflections with 2 < 50°were collected; of these, 3532 with Zobsd > 3 ( ) were used in the structure derivation giving final conventional values of R = 0.027 and Z?w = 0.031 (the number of parameters refined in the last full-matrix least-squares cycle was 280). The coordination geometry of the Ta is severely distorted from the trigonal-prismatic geometry observed in the corresponding Nb structure, in accord with our expectations based on spectral differences. The average Ta-S bond length, 2.43 (1) A, is very similar to the one found in Nb. The distortion is quite unique with two of the chelate rings being close to the prismatic limit while the third one is twisted about the twofold axis of the prism to the octahedral extreme; the individual twist angles are 16, 16, and 54°. As a result, the two triangular faces are no longer parallel but inclined by 12°. The relevance of the observed distortion to the factors affecting the trigonal-prismatic geometry is discussed.