Quantum mechanics

Orthorhombic crystal system

Crystal structure

Center (category theory)

Physics

Chloride

Organic chemistry

Point reflection

Condensed matter physics

Crystallography

Chemistry

Absorption spectroscopy

Bond length

Bulletin of the Chemical Society of Japan

The crystal structure of μ-oxo-bis{pentamminechromium(III)} chloride (basic rhodochromic chloride) monohydrate, [(NH3)5Cr–O–Cr(NH3)5]Cl4·H2O, has been determined from the three-dimensional X-ray data. The crystals are orthorhombic. The cell dimensions are: a=11.94±0.01, b=11.71±0.01, and c=13.40±0.02 Å. The space group is Pbca, with four formula units in a unit cell. The structure was refined by the least-squares method, with anisotropic temperature factors, to R=0.14. A bridging oxygen atom of the basic rhodochromic complex ion is situated on the inversion center. Therefore, the complex has a center of symmetry and, accordingly, a linear Cr–O–Cr system. The N–Cr–O angles are nearly 90° or 180°, and the Cr–N bond distances are in the range from 2.09 to 2.14 Å (average 2.11 Å). The complex ion has approximately a D4h symmetry. The Cr–O distance is 1.80 Å, which is quite short compared with that found in the other Cr(III) complexes. The linear Cr–O–Cr system and its short bond distance suggest the presence of an extensive π-bonding in this system. The single-crystal polarized absorption spectra in the visible and ultraviolet regions were also measured. It was found that the characteristic sharp absorption bands of the basic rhodochromic complex ion are all polarized along the fourfold rotation axis of the complex.

The Crystal Structure of μ-Oxo-bis{pentamminechromium(III)} Chloride Monohydrate, [(NH3)5Cr-O-Cr(NH3)5]Cl4·H2O