The correct name for the complex $\left[Cr{\left(N{H}_3\right)}_6\right] \left[Co{\left(C_2{O}_4\right)}_3\right]$ is 

Hexaammine chromium (III), tri oxalato cobaltate (III)

Hexaammine chromium (III), tri oxalato chloride (III)

Hexaammine chromate (III), tri oxalato cobaltate (III)

Hexaammine chromate (III), tri oxalato cobalt (III)