Question

A cobalt(III) centre form a complex with five ammine ligands, and ONE sulfate counter ion. What is its likely formulation?

Answer 1

Given the formula, the sulfate probably occupies the `1` coordination site on the octahedral cobalt centre.

Explanation:

Given this formulation, the parent complex ion is likely, `[Co(NH_3)_5(OSO_3)]^+`, in which the sulfato ligand acts as a unidentate donor towards the octahedral `Co(III)` centre. I don't know the lingo with respect to secondary and primary valences.