Further structural analysis of Cr(III) oligomers in weakly acidic solutions

Three chromium(III) hydrolytic oligomers (monomer, dimer, and trimer) were isolated via cation-exchange from weakly acidic solutions, and their structures were elucidated with multiple techniques including UV–Vis and infrared (IR), electron paramagnetic resonance (EPR), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results indicate that the monomer has an octahedral symmetry with six water molecules at its six apices. In the dimer, two Cr(III) ions, each of which has an octahedral coordination symmetry distorted by the stretching along the CrCr joining axis, are doubly bridged by two hydroxyl groups. Suggested by the data from EXAFS and EPR, the trimer in solution may form with an irregular triangular configuration, in which two Cr(III) ions are doubly bridged by hydroxyl groups and the third Cr(III) ion is connected to each of the two through single-hydroxyl bridging.

Three fundamental chromium(III) hydrolytic oligomers (monomer, dimer, and trimer) were isolated from weakly acidic solutions and their structures were elucidated with multiple techniques including UV–Vis and infrared (IR), electron paramagnetic resonance (EPR), and extended X-ray absorption fine structure (EXAFS) spectroscopy.Figure optionsDownload as PowerPoint slide