The Crystal and Molecular Structure of Acetamidopentaamminecobalt(III) Perchlorate. A Conjugate Base of Nitrogen Bonded Acetamide

Abstract

The crystal and molecular structure of acetamidopentaamminecobalt(III) perchlorate, [CH3CONHCo(NH3)5]2+•2ClO4−, has been determined from three-dimensional X-ray data obtained by diffractometer methods. The crystals are monoclinic, space group [Formula: see text] with four formula units in a unit cell of dimensions a = 13.250(6), b = 10.318(6), c = 10.676(5) Å, β = 98.34(3)°. The structure has been refined by block-diagonal least-squares methods with anisotropic thermal parameters to a final residual R of 0.055 for 1340 observed reflexions. The crystal structure consists of discrete octahedral cations and tetrahedral perchlorate anions. The Co—N (amide) distance is short (1.911(8) Å) while the trans Co—N (ammine) bond is long (1.994(8) Å) compared to the equatorial Co—N distances which average 1.963(13) Å. The bond distances in the amide group, C—O 1.267(12) Å and C—N 1.339(12) Å, indicate that a delocalized system plays an important role in the ground state structure of the cation.