Question 20.3: Name each of the following: (a) [Co(NH3)6]Cl3, prepared in 1......
Name each of the following:
(a) [Co(NH_{3})_{6}]Cl_{3}, prepared in 1798 by B. M. Tassaert and generally considered to be the first coordination compound
(b) [Rh(NH_{3})_{5}I]I_{2}, a yellow compound obtained by heating [Rh(NH_{3})_{5}(H_{2}O)]I_{3} at 100 °C
(c) Fe(CO)_{5}, a highly toxic, volatile liquid
(d) [PtCl_{4}]^{2-}, a reddish orange salt used as a reagent in the preparation of other coordination complexes of platinum.
STRATEGY
First determine the oxidation state of the metal, as in Worked Example 20.2. Then apply the seven rules above to name the compound or ion.
(a) Because the chloride ion has a charge of -1 and ammonia is neutral, the oxidation state of cobalt is +3. Use the prefix hexato indicate that the cation contains six NH_{3} ligands, and use a Roman numeral III in parentheses to indicate the oxidation state of cobalt. The name of [Co(NH_{3})_{6}]Cl_{3} is hexaamminecobalt(III) chloride.
(b) Because the iodide ion has a charge of -1, the complex cation is [Rh(NH_{3})_{5}I]^{2+} and the rhodium has an oxidation state of +3. List the ammine ligands before the iodo ligand, and use the prefix penta- to indicate the presence of five NH_{3} ligands. The name of [Rh(NH_{3})_{5}I]I_{2} is pentaammineiodorhodium(III) iodide.
(c) Because the carbonyl ligand is neutral, the oxidation state of iron is zero. The systematic name of Fe(CO)_{5} is pentacarbonyliron(0), but the common name iron pentacarbonyl is often used.
(d) Because each chloride ligand (Cl^{-}) has a charge of -1 and because [PtCl_{4}]^{2-} has an overall charge of -2, platinum must have an oxidation state of +2. Use the name platinate(II) for the metal because the complex is an anion. The name of [PtCl_{4}]^{2-}, is the tetrachloroplatinate(II) ion.