The Crystal and Molecular Structure of the High-Spin Square-Planar Complex Triphenylmethylarsonium Bis(toluene-3,4-dithiolato)cobaltate-0.5-Ethanol

Richard Eisenberg*, Zvi Dori, Harry B. Gray, James A. Ibers

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


The crystal and molecular structure of the high-spin complex triphenylmethylarsonium bis (toluene-3,4-dithiolato)cobaltate-0.5-ethanol, [(C6H6)3(CH3)As] [Co(tdt)2] · 0.5C2H6OH, has been determined from three-dimensional single-crystal X-ray data collected by counter methods. The structure has been refined by least-squares procedures to a conventional R factor of 0.063 for 1108 nonzero reflections. The complex crystallizes in space group PI of the triclinic system with two molecules in a unit cell of dimensions a = 18.61 ± 0.01, b = 10.848 ± 0.006, c = 10.206 ± 0.005 Å, a = 112.45 ± 0.02°, β = 71.55 ± 0.02°, γ = 115.90 ± 0.02°, and V = 1685.4 Å3. An observed density of 1.359 ± 0.010 g/cm3 is in excellent agreement with the calculated value of 1.355 g/cm3 for Z = 2. The Co(tdt)2 anions are crystallographically required to have centers of symmetry since the two cobalts per unit cell occupy the (0, 0, 0) and (1/2, 0, 1/2) special positions of the space group. The S4 coordination about the cobalts is very nearly square planar with average intra- and interligand S-S distances of 3.098 and 3.028 Å, respectively, and estimated standard deviations for these values of 0.007 Å. The planar Co(tdt)2 anions have an ordered trans configuration of the tdt ligand methyl groups and thus possess C2h symmetry. The (C6H5)3(CH3)As + cation has its expected tetrahedral geometry about arsenic. Ethanol solvent molecules were trapped during crystallization of the complex, presumably because of the asymmetric nature of the cation. These solvent molecules are disordered about the (0, 1/2, 0) center of symmetry with only one molecule per unit cell. Thus, the crystal structure of the complex consists of the packing of essentially planar anions, bulky cations, and trapped solvent molecules. The anions are well separated and exhibit none of the magnetic interactions which characterize the structures of the other related mononegative bis complexes. A ground-state electronic structural assignment for the spin-triplet Co(tdt)2 complex is proposed on the basis of molecular orbitals calculated for a closely related nickel complex using the observed structural parameters.

Original languageEnglish (US)
Pages (from-to)741-748
Number of pages8
JournalInorganic Chemistry
Issue number4
StatePublished - Apr 1 1968

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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