Which of the following DOES NOT obey the EAN rule ?
By BYJU'S Exam Prep
Updated on: October 17th, 2023
(A) Mn2(CO)10
(B) Cr(CO)6
(C) V(CO)6
(D) Fe(CO)5
V(CO)6 does not obey the EAN rule. Sidgwick provides the EAN Rule. The EAN rule states that a metal’s EAN is equal to the total of its own electrons plus any electrons provided by its ligands, and that it is also equal to the atomic number of the following noble gas.
Table of content
EAN Rule in Chemistry
Organometallic complexes are subject to the EAN rule. Here are some points.
- The 18-electron rule and this rule are comparable.
- This rule states that valence electrons of metal ions or transition metals add up to 18 in total.
- Complexes that adhere to the EAN rule are regarded as stable.
- The 18-electron rule is typically followed by the transition metal carbonyls’ first row.
- Many complexes do not adhere to the 18-electron rule.
- The transition metals that are located on the left side of the periodic table combine to generate these complexes.
Explanation:
Mn2(CO)10
- The compound contains manganese with a zero oxidation state.
- Each unit of carbonyl contributes two electrons, making it a neutral ligand.
- Manganese contributes 7 electrons to the total.
- One electron comes from the Mn-Mn bond’s contribution.
- As a result, the contribution of the metals and ligands is as follows: 7 + 1 + 2 × 5 = 18.
- The molecule thus adheres to the 18 electron rule.
Cr(CO)6
- Six electrons come from the chromium.
- 6 × 2 = 12 is the contribution from the six carbonyl ligands.
- Consequently, there are 12 + 6 = 18 outermost electrons in all.
- The molecule thus adheres to the 18 electron rule.
V(CO)6
- Vanadium makes a contribution of 5 electrons.
- 6 × 2 = 12 is the contribution from the six carbonyl ligands.
- Consequently, there are 12 + 5 = 17 outermost electrons in all.
- The molecule does not follow the 18-electron rule as a result.
Fe(CO)5
- Eight electrons are contributed by the iron.
- Contribution from the five carbonyl ligands is 5 x 2 = 10, and the molecule complies with the 18 electron rule because the total number of outermost electrons is 10 + 8 = 18.
Therefore, the molecule that does not obey the EAN rule is V(CO)6.
Summary:
Which of the following DOES NOT obey the EAN rule? (A) Mn2(CO)10 (B) Cr(CO)6 (C) V(CO)6 (D) Fe(CO)5
The molecule that does not obey the EAN rule is V(CO)6. The EAN rule is often referred to as the 18-electron rule. Atomic number of the metal +(Number of ligands x electrons donated by each ligand) – positive oxidation state of the metal.
