Name the following coordination compounds. Which one(s) exhibit(s) isomerism? Explain. (a) \(\left[\operatorname{CoBr}\left(\mathrm{NH}_{3}\right)_{5}\right] \mathrm{SO}_{4}\) (b) \(\left[\operatorname{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right]\left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) (c) \(\mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]\) (d) \(\left[\mathrm{Co}(\mathrm{en})_{3}\right] \mathrm{Cl}_{3}\)

To name the compounds, follow the IUPAC rules: Name the ligands first, in alphabetical order, and then the metal atom/ion. Prefixes indicating the number of ligands are not used for ordering. Also, use Roman numerals in parentheses to indicate the oxidation state of the metal. A. The name for \(\left[\operatorname{CoBr}(\mathrm{NH}_{3})_{5}\right]\mathrm{SO}_{4}\) is 'Pentaamminebromocobalt(III) sulfate' B. The name for \(\left[\operatorname{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right] \left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) is 'Hexaamminechromium(III) hexacyanocobaltate(III)' C. The name for \(\mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]\) is 'Sodium hexanitritocobaltate(III)' D. The name for \(\left[\mathrm{Co}(\mathrm{en})_{3}\right] \mathrm{Cl}_{3}\) is 'Tris(ethylenediamine)cobalt(III) chloride'

An understanding of isomers in coordination chemistry is required. Isomers are distinct compounds that share the same chemical formula. However, their atoms, ions or molecules are arranged differently. A. \(\left[\operatorname{CoBr}(\mathrm{NH}_{3})_{5}\right]\mathrm{SO}_{4}\) does not exhibit isomerism. B. \(\left[\operatorname{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right]\left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) does not exhibit isomerism. C. \(\mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]\) does not exhibit isomerism. D. \(\left[\mathrm{Co}(\mathrm{en})_{3}\right] \mathrm{Cl}_{3}\) can exhibit geometric isomerism due to the presence of the bidentate ligand ethylenediamine \( \mathrm{en} \). Different arrangements of the \( \mathrm{en} \) around the \(\mathrm{Co}\) creates geometric isomers (fac- and mer-).