Answer
Diamminedicyanoplatinum(II)
Work Step by Step
Name for $NH_{3}$ ligand is ammine and that for CN is cyano. Ligands are named in alphabetical order. We prefix 'di' to indicate that the number of ligands is two. As the complex ion is neutral, the metal is named same as the element, that is, platinum.
Oxidation state of Pt= Charge on complex-(2$\times$charge of CN)= 0-(2$\times$-1)= 2.
Oxidation state is indicated by Roman numeral in parenthesis.
