Question

Write the formulas for the following coordination compounds :
a.) Tetraammineaquachloridocobalt (III) chloride
b.) Potassium tetrahydroxidozincate(II)
c.) Potassium trioxalatoaluminate(III)
d.) Dichloridobis(ethane- 1,2-diamine) cobalt(III)
e.) Tetracarbonylnickel (0)

Answer 1

The coordination complex formula is written in square brackets. First, the chemical symbol of the central metal atom is written and then the ligands. In some cases, we have some metal atom which is before the complete name, then such an atom should be written before the square bracket. The roman numerals written with metal atoms describe the oxidation state of metal in complex.

Complete answer:
We know that coordination chemistry is the most colourful chemistry.
The coordination complexes have a different set of rules that are used for their nomenclature. The central metal of the complex is written first followed by ligands. The roman numerals in the name represent the oxidation state of metal in coordination complexes. Some ligands possess charges and some are neutral. The charge may be positive or negative. One needs to balance the charges in formula in order to get the accurate oxidation state of metal. The names of the above complexes are -
a.) Tetraammineaquachloridocobalt (III) chloride = $[CO{({H_2}O)_2}{(N{H_3})_4}]C{l_3}$
b.) Potassium tetrahydroxidozincate(II) = ${[Zn{(OH)_4}]^{2 - }}$
c.) Potassium trioxalatoaluminate(III) = ${K_3}[Al{({C_2}{O_4})_3}]$
d.) Dichloridobis(ethane- 1,2-diamine) cobalt(III) = ${[CoC{l_2}{(en)_2}]^{1 - }}$
e.) Tetracarbonylnickel (0) = $[Ni{(CO)_4}]$

Note:
In some complexes, the metal atom is written before the complete name. In that case, the metal is bonded to rest with ionic bonds. For example - in Potassium tetrahydroxidozincate(II). Here, the potassium is not part of the metal complex. So, it could not be written in square brackets.