Redetermination of the crystal structure of chloropentamminecobalt(III) dichloride

Abstract

The crystal structure of [Co(NH3)5C1]CI2 has been redetermined from three-dimensional counter data at room temperature. The crystals are orthorhombic (Pnma) with lattice constants a = 13.26, b = 10.34, both + 0.01, and c= 6-72_+ 0.005 ,~. The structure is made up of molecular ions, Co(NH3)sCI2+ and C1-ions, separated by ordinary van der Waals distances. There is no evidence for a trans distortion of the Co-N bond by the Co-Cl bond. The four independent Co-N distances were found to be: 1"962_ 0.004, 1.964 + 0.006, 1.978 _ 0.006 and 1"998_+ 0.006/~. The nitrogen associated with the longest Co-N distance appears to be involved in a N-CI intermolecular hydrogen bond.

trans-Dichlorotetraamminecobalt(III) bisulfate

“…In a recent survey of 11 pentaammine cobalt(III) structures, the weighted mean value for the Co-N distance was 1.969A (Fronczek, 1975). The two Co-C1 distances are effectively equal with an average value, 2.255 (2) A, slightly shorter than 2.286A reported in [Co(NH3)sCI]CI2 (Messmer & Amma, 1968). The S-O distances in the bisulfate ion are in good agreement with those reported in K0.ssRb0.4sHSO4 and RbHSO4 (Mumme, 1973), and in (NH3)sCoO2Co(NH3)s(SO4)(HSO4)3 (Schaefer & Marsh, 1966).…”

Revisiting the crystal structure of [Co(NH3)5Cl]Cl2 using synchrotron powder diffraction: to what extent single-crystal diffraction from 1960s got it right?

“…It has been pointed out (Toby, 2006) that the best way to judge the correctness of a model from powders is: (1) graphically and carefully observing the experimental and calculated Rietveld profiles; and (2) confirming that the chemical bonding in the model is plausible. For this material, since powder and single-crystal diffraction give rise to crystal structure descriptions in two space groups, Pnma and Pn 2 1 a , respectively, and unresolved subtleties in the internal geometry of the coordination complex still remained after the work of Messmer and Amma (1968); the Rietveld method was also used to further assess the validity of the published models from single-crystal diffraction (Shigeta et al , 1963; Messmer and Amma, 1968), comparing their Rietveld agreement factors and Rietveld graphs with those of the model from powders.…”

“…Towards facilitating the comparison of all three models and their Rietveld refinements, Figure 3 shows the crystal packing in the three models, and Figure 4 shows the reported coordination complex geometry using the labeling scheme of the respective publications (Shigeta et al , 1963; Messmer and Amma, 1968). Table IV summarizes the Rietveld agreement factors, Fourier difference residuals, and the number of parameters refined in each fit, all of which were carried out using our synchrotron powder diffraction data (this work).…”

“…This article describes such case revealed through the redetermination of the crystal structure of [Co(NH 3 ) 5 Cl]Cl 2 , the “purpureo salt,” previously reported from X-ray single-crystal diffraction in the space group Pnma (No. 62) (Shigeta et al , 1963; Messmer and Amma, 1968). The analysis of its modern synchrotron X-ray powder diffraction data indicates that the space group is Pn 2 1 a (No.…”

F-test in EXAFS fitting of structural models

“…We have studied the case of a very simple and well known coordination complex ion : [Co(NH3)sCI] 2+ . The crystal structure gives RI(Co-N) = 1.97 ]k and R2 (Co-CI) =2.27 A (Messmer, 1968).…”