Which of the following organometallic compound is $\sigma -$ and $\pi -$bonded?

• A

  $\mathrm{Fe}{\left({\mathrm{CH}}_3\right)}_3$

• B

  $\left[Fe{\left({\eta }^5-C_5{H}_5\right)}_2\right]$

• C

  ${\left[\mathrm{Co}{\left(\mathrm{CO}\right)}_5{\mathrm{NH}}_3\right]}^{2+}$

• D

  $\mathrm{K}\left[{\mathrm{PtCl}}_3\left({\mathrm{\eta }}^2-{\mathrm{C}}_2{\mathrm{H}}_4\right)\right]$