Question

V(CO)6- is very inert in the presence of triphenylphosphine. That is, none of the carbonyl ligands will be substituted by the phosphine.

1. Why is this complex so inert?

2. How might one make this complex more reactive?

Answer 1

V(CO)6 complex

1. In the coordination complexes, bulky ligands or ligands that may form a pi-back bonding structure prevents the approach of ligands to the metal center and carryout reactions. This type of complex behaves as an inert complex such as V(CO)6-. when in V(CO)6- state, the total effective atomic number (EAN) of the central metal V calculated for the complex is,

EAN = 23 + 1 + 12 =  36

which matched with the atomic number and electron count of inert gas next in the series. this thus makes the complex V(CO)6- inert in nature similar to inert gas reactivity.

2. Upon oxidation with say H3PO4 it gives reactive V(CO)6 state which can be easily reacted with other ligands.