Synergic bonds in organo – metallic compounds `[M(CO_(4)]` leads to :

Options

A. Shortening of M - CO bond
B. Lengthening of M - CO bond
C. No effect
D. None of these

Explanation

To solve the question regarding the effect of synergic bonds in organometallic compounds like `[M(CO)4]`, we will follow these steps:

### Step 1: Understand Organometallic Compounds
Organometallic compounds are defined as compounds that contain a bond between a metal and a carbon atom. In this case, we are looking at a compound where the metal (M) is bonded to four carbonyl (CO) groups.

**Hint:** Remember that organometallic compounds involve a direct bond between metal and carbon.

### Step 2: Define Synergic Bonding
Synergic bonding refers to a type of bonding where there is both a donation of electrons from the ligand (in this case, the carbonyl group) to the metal (forming a sigma bond) and a back-donation of electrons from the filled d-orbitals of the metal to the empty pi* (pi star) orbitals of the carbonyl group.

**Hint:** Focus on the concept of electron donation and back-donation in the bonding process.

### Step 3: Analyze the Bonding in `[M(CO)4]`
In `[M(CO)4]`, each carbonyl group (CO) acts as a ligand. The carbonyl group donates electrons to the metal, forming a sigma bond. Simultaneously, the metal donates electrons from its filled d-orbitals to the empty pi* orbitals of the carbonyl, creating a synergic bond.

**Hint:** Consider how the interaction between the metal and carbonyl groups enhances the overall bonding.

### Step 4: Determine the Effect on Bond Length
Due to the synergic bonding, the bond between the metal and carbon (M-C) acquires a double bond character. This is because the back-donation from the metal to the carbonyl increases the effective bond order between the metal and carbon.

**Hint:** Recall that increased bond order typically results in shorter bond lengths.

### Step 5: Conclusion on Bond Length
Since the M-C bond transitions from having single bond character to having double bond character due to the synergic bonding, the bond length decreases. Therefore, we conclude that the synergic bonding leads to the shortening of the M-C bond in `[M(CO)4]`.

**Hint:** Remember that single bonds are longer than double bonds, which is key to understanding the effect on bond length.

### Final Answer
The synergic bonds in organometallic compounds `[M(CO)4]` lead to the shortening of the M-C bond.

**Correct Option:** Shortening of MCO bond.