Several coordination isomers, with both Co and Cr as$3+$ions, have the molecular formula ${\text{CoCrC}}_6{\text{H}}_{18}{\text{N}}_{12}$

(a) Give the name and formula of the isomer in which the Co complex ion has six ${\text{NH}}_3$groups.

(b) Give the name and formula of the isomer in which the Co complex ion has one$CN$and five $N{H}_3$groups.

Coordination isomers, with both Co and Cr as $3+$ions, have the molecular formula $CoCr{C}_6{H}_{18}{N}_{12}$.

To solve problems like this, mention some rules for naming coordination compounds:

• Cation is known as before anion
• Within thecomplex ion, name ligands before metal ion, in alphabetical order
• A numerical prefix is that the number of ligands of type
• The number of metal ion is written by roman numerals in parentheses if the metal ion has over one number
• If the complex ion is an anion, add -ate rather than the ending of metal name
  Neutral ligands most frequently have molecule name, but anionic ligands lose the - ide and add -o after the basis name

${\text{CoCrC}}_6{\text{H}}_{18}{\text{N}}_{12}$- molecular formula

a) complex ion has groups, which means, look at the molecular formula, that Cr complex ion has 6CN groups:

localid="1663344958144" $\left(Co{\left(N{H}_3\right)}_6\right)\left(Cr{\left(CN\right)}_6\right)-hexaminecobalt\left(III\right)hexacyanochromate\left(III\right)$

b) Co complex ion has one CN and five $N{H}_3$groups, which means, look at the molecular formula, that Crcomplex ion has one $N{H}_3$and five $CN$groups:

$\left(Co{\left(N{H}_3\right)}_{5}CN\right)\left(CrNH{H}_3{\left(CN\right)}_5\right)-pentaamminecyanocobalt\left(III\right)amminepentacyanochromat\left(III\right)$