The chemistry of oxo- and hydroxo-bridged chromium (III) dimers with aromatic amine ligands



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Texas Tech University


The chemistry of Cr(III) dimers with a linear oxygen bridge has seen a considerable amount of interest since the discovery of the (|l-oxo)bis pentaainminechromium(in)} (basic rhodo) dimer by Jorgensen (1882).i This interest is due to markedly different substitutional and spectral properties over those of simple Cr(in) monomers, a manifestation of the very different bonding that occurs as a result of the linear Cr-O-Cr unit. For example, the loss of NH3 in aqueous base from the basic rhodo cation occurs in just nainutes,^ whUe the loss of NH3 from Cr(NH3)53+ occurs over several days.^ In addition, the intense transitions in the UV-visible spectrum of the basic rhodo cation are in sharp contrast to the well known, very broad, weak d-d transitions seen in Cr(III) monomeric species.