Crystal structure and absolute configuration of (+) 546 ‐[copy 4 Cl 2 ]HDBT: An example of torsional isomerism

The crystal structure and absolute configuration of the (−) 589 ‐dibenzoylmonohydrogentartrate salt of the cation [Co(pyridine) 4 Cl 2 ] + have been determined from a three‐dimensional X‐ray analysis. Single crystals were grown from dimethylsulfoxide: space group P 2 1 2 1 2 1 , Z = 4, and cell dimensions a = 21.463(4), b = 23.112(3), and c = 7.490(1) Å. Full‐matrix least‐squares refinement on F converged at R = 0.075, 196 variables and 2029 observations. The cation has pseudotetragonal coordinate geometry, with axial Cl and equatorial N atoms. The dihedral angles between the pyridine ligands and the equatorial plane are 47(1), 39(1), 50(1), and 45(1)° and torsional isomerism is responsible for the solid‐state chiroptical properties of the cation. The preferential crystallization of the P atropisomer of the cation is attributed to a general electrostatic attraction between cation and anion.