Which of the following statements is correct with respect to the metal carbonyls of `I^(st)` transition series?

Options

A. As `M-Cpi` bonding increasing, the C-O bond length increases.
B. As positive charge on the central metal atom increases, the C-O bond length increases.
C. As electron density on the central metal atom increases, the C-O bond length increases.
D. (A) and ( C) both.

Answer

D

Explanation

Order of C-O bond strength:
`[Mn(CO)_(6)^(+) gt [Cr(CO)_(6)] gt [V(CO)_(6)]^(-) gt [Ti(CO)_(6)]^(2-) and [NI(CO)_(4)] gt [Co(CO)_(4)]^(-) gt [Fe)CO)_(4)]^(2-)`.
(A) True statement.
(B)As+ve charge on the central metal atom increases, the less readily the metal can donate electron density into the `pi^(***)` orbitals CO ligand to weaken the C-O bond.
( C) In the carbonylate anions, the metal has a greater electron density to be dispersed, with the result that `M-Cpi` bonding is enhanced and the C-O bond is diminished in strength.