Synthesis and characterization of some chromium (III) complexes
Koehlert, Donna E.
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Complexes of the type [Cr(en)₂FX]ⁿ⁺, where X is a strongly basic anion, were synthesized and characterized in this research. The procedures for making these compounds vary, depending on the isomer desired and the starting material used. Complexes of the type [Cr(en)₂FX]ⁿ⁺ can be easily prepared by reacting the corresponding fluoroaqua complexes with the appropriate ammonium salt in methanol; however, this procedure cannot be used if X is a strongly basic anion. If the leaving group was dimethylsulfoxide, rather than water, entry of the strongly basic anion became relatively easy. A procedure based on this fact was developed and used to synthesize the cis-[Cr(en)₂FCN]⁺ ion, the cis-[Cr(en)₂FN₃]⁺ ion, and to attempt to prepare the cis- 2+ [Cr(en)₂Fpy]²⁺ ion. A procedure different from the cis synthesis was necessary in order to obtain the corresponding trans isomer. Addition of a strongly basic anion to the trans-fluorodimethylsulfoxo starting material causes swift and essentially complete trans to cis isomerization to take place before anation takes place. To obtain the trans isomer it was necessary to make the trans-bromofluoro complex and attempt to find a procedure that would allow coordination of the basic anion without causing isomerization. filost of the complexes described were characterized by elemental analyses, electronic absorption spectroscopy, infrared absorption spectroscopy, and in one case single crystal x-ray diffraction.