$($b$)$ Specifying the suitable reaction conditions, suggest reasonable synthesis for

$($i$)Mo(C_6{H}_6)(CO{)}_3$

$($ii$)Mo(C_6{H}_6{)}_2$

$($iii$)$ a compound containing $[Co(C_5{H}_5{)}_2{]}^{+}$and

$($iv$)Si{H}_{3}Co(CO{)}_4.$