Crystal and molecular structure of tetraphenylarsonium tris(benzenedithiolato)tantalate(V)

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.

Nicht-VSEPR-Strukturen und chemische Bindung in d0-Systemen

“…In neuerer Zeit wurden die ersten nichtoktaedrischen sechsfach koordinierten Komplexe mit einzähnigen Thiolatliganden beschrieben. ¾hnliche Verzerrungen wurden bereits früher beobachtet, [95] und bei heteroleptischen Komplexen erlangen sie gröûere Bedeutung (Abschnitt 4.3). In Abhängigkeit von der jeweiligen Elektronenkonfiguration, vom Ligandentyp, vom Metallzentrum sowie von Wechselwirkungen mit Gegenionen decken diese Strukturen den gesamten Bereich von oktaedrischer bis trigonal-prismatischer Koordination ab.…”

Electronic Control of the “Bailar Twist” in Formally d0-d2 Molybdenum Tris(dithiolene) Complexes: A Sulfur K-edge X-ray Absorption Spectroscopy and Density Functional Theory Study

“…Indeed, crystallographic investigations showed that tris(dithiolene) complexes such as [Mo(mnt) 3 ] 2-(mnt = maleonitriledithiolate(2-)) and [Mo(bdt) 3 ] 1-(bdt = benzene-1,2-dithiolate(2-)) adopt a geometry between trigonal prismatic and octahedral; 6,7 however, there are some notable exceptions such as [Mo(mdt) 3 ] z (mdt = 1,2-dimethylethene-1,2-dithiolate(2-), z = 2-, 1-), where the Mo-S 6 trigonal prism is maintained throughout the series, and [Ta(bdt) 3 ] 1-, which is isoelectronic with [Mo(S 2 C 2 H 2 ) 3 ] but forms a distorted octahedron. [8][9][10] Another factor thought to stabilize the trigonal prism was interligand sulfur-sulfur bonding. However, this was refuted by comparing the S-S distances in the trigonal prismatic complexes [Mo(bdt) 3 Rotation about the C 3 axis from O h (θ = 60°) to D 3h (θ= 0°), which is the pathway used to explain the racemization of certain octahedral tris(chelate) complexes, is known as a Bailar twist (Scheme 1b, θ).…”

Trigonal prismatic versus octahedral coordination geometry of transition metal dithiolates: Comparison between saturated and unsaturated early transition metal tris(1,2-dithiolate) complexes

“…Although the decreasing stability of TP geometry in the order Mo > Nb > Zr suggested to Cowie and Bennett (1 1) that the proper matching of metal d-orbital and ligand orbital energies was an important condition for TP geometry, the study was not conclusive because the change in overall charge of the complexes should also favor the observed trend. To confirm the hypothesis of Cowie and Bennett, we undertook structural analysis of Ta(bdt)3-and Sb(bdt)3-complexes, which strongly resemble the Nb complex in metal size and also have the same charge (12,16). The increasing distortion away from TP geometry in the order Nb < Ta < Sb provides substantial evidence that the stability of TP Can.…”

“…All other features were less than 0.37e/A3. The programs used in this study are those described previously (12). Atomic coordinates and equivalent isotropic thermal parameters for the complex anion ~b ( e d t )~~-are listed in Table 4.…”

“…In 1965 the first observation of a discrete TP complex, Re(l ,2,-S2C2Ph2)3 (3), rekindled interest in TP geometry and since then a host of factors, such as (a) ligand constraint (4,5), (b) ligand field stabilization energy (2,4,6), (c) interdonor atom bonding (3,(7)(8)(9), (d) proper matching of ligand and metal orbital energies (1,2,(10)(11)(12), (e) the symmetry of ligand n orbitals (2,8,13), and (f) the overall charge of the complex, have been suggested as important factors influencing the formation of TP, octahedral, or intermediate geometries. From experimental work of Holm and co-workers (4) and Eatough et al (14) and theoretical work of Holm (4), Kepert ( 3 , and Wentworth (6) it appears that the two most important factors involved are probably the ligand constraint (provided by cage type 'present address: Phillips Petroleum Co., 96-G PRC, Bartlesville, OK 74004, U.S.A.…”