The correct statement(s) regarding the binary transition metal carbonyl compounds is (are) (Atomic numbers: )
- (A)Total number of valence shell electrons at metal centre in or is 16
- (B)These are predominantly low spin in nature✓ Correct
- (C)Metal-carbon bond strengthens when the oxidation state of the metal is lowered✓ Correct
- (D)The carbonyl C-O bond weakens when the oxidation state of the metal is increased
Answer: (B), (C)
Solution
(A) Both and follow the 18-electron rule, not 16.
(B) CO is a strong-field ligand, so metal carbonyl compounds are predominantly low spin complexes.
(C) The metal-carbon bond involves synergic bonding: . Back-bonding increases the strength of the M-C bond. When the metal is more electron-rich (lower oxidation state), back-bonding is stronger, strengthening the M-C bond.
(D) When the oxidation state of the metal increases, the metal becomes less electron-rich, reducing back-bonding. This strengthens the C-O bond, not weakens it.
Correct answers: (B) and (C).
(B) CO is a strong-field ligand, so metal carbonyl compounds are predominantly low spin complexes.
(C) The metal-carbon bond involves synergic bonding: . Back-bonding increases the strength of the M-C bond. When the metal is more electron-rich (lower oxidation state), back-bonding is stronger, strengthening the M-C bond.
(D) When the oxidation state of the metal increases, the metal becomes less electron-rich, reducing back-bonding. This strengthens the C-O bond, not weakens it.
Correct answers: (B) and (C).
JEE Advanced · 2018 · 20 May 2018 · Paper 1 · One or more correct options