Consider the following complexes.
(P) `[Cr(CO)_(5)(PF_(3))]" "(Q) [Cr(CO)_(5)(PCl_(3))]`
Select the correct options.

Options

A. Both P and Q have longer CO bond length than free CO molecule.
B. P has shorter CO bond length than Q.
C. P has longer Cr-C bond length than Q.
D. `PF_(3)` is a better `pi-a c c e p t o r` than `PCl_(3)`.

Answer

A, B, C, D

Explanation

Due to back donation C-O bond length in given compounds is longer than free CO molecule. `PE_(3)` is better `pi`-acceptor than CO, hence back donation is more favoured towards `PF_(3)`rather than CO and `PF_(3)` is is better `pi`-acceptor than `PCl_(3)` hence `pi`-donation is more favourable in (P) than(Q). Hence,CO length in (P) is shorter than (Q). Due to less `pi`-donations towards CO or C bond is longer in (P) than (Q).