Among the following which is not the \\pi -bonded organometallic compound? (2003)

{\K}[{\PtCl}_{3}({\\eta}^{2}-{\C}_{2} {\H}_{4})]

{\Fe}(\\eta^{5}-{\C}_{5} {\H}_{5})_{2}

{\Cr}(\\eta^{6}-{\C}_{6} {\H}_{6})_{2}