The sum of oxidation states  of ’Cr’  in 

$\text{i) }[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6]{\mathrm{Cl}}_3\text{ii) }\left[\mathrm{Cr}{\left({\mathrm{C}}_6{\mathrm{H}}_6\right)}_2\right] \text{iii) }{\mathrm{K}}_2\left[\mathrm{Cr}\right(\mathrm{CN}{)}_2\left(\mathrm{O}{)}_2\left({\mathrm{O}}_2\right)\left({\mathrm{NH}}_3\right)\right]$  is…..

NICKEL $M{L}_5$ complex is square pyramidal

$\begin{array}{l}{180}^0=2\\ {90}^0=8(4insquareplanan,4=perpendiculartoplane)\end{array}$

$Fe:M{L}_{5}complexistrigonalbipyramidal$