Let the oxidation state of $P t=x$, then

$(x \times 1)+3 \times(0)+(1 \times-1)+(1 \times-1)+(1 \times-1)=+1$

$x-3=+1$

$x=+4$

Thus, the $I U P A C$ name of the complex $\left[P t(N H)_{3} B r\left(N O_{2}\right) C l\right] C l$ is triamine bromidochloridonitro platinum $(IV)$ chloride as the names of the different ligands are arranged alphabetically.