In the complex, ${\mathrm{CoCl}}_3. 3{\mathrm{NH}}_3$, only secondary valency but not primary valency of the central metal is satisfied by

According to Werner's theory, primary valency of a metal is satisfied by negative ions only.

Werner formula …${\mathrm{CoCl}}_3. 3{\mathrm{NH}}_3$

Modern formula . . .$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$

Three chloride ions satisfy both primary and secondary valency. 

Three ammonia molecules satisfy secondary valency only.