Among the following, the correct statement(s) is(are) :

Options

A. `Al(CH_3)_3` has the three-centre two- electron bonds in its dimeric structure
B. `BH_3` has the three-centre two-electron bonds in its dimeric structure
C. The Lewis acidity of `BCl_3` is greater than that of `AlCl_3`
D. `AlCl_3` has the three-centre two-electron bonds in its dimeric structure

Answer

To determine which statements are correct among the given options regarding chemical bonding, we will analyze each statement step by step.

### Step 1: Analyze the first statement about Al(CH3)3
- **Statement**: Al(CH3)3 has three-centered two-electron bonds in its dimeric structure.
- **Analysis**: In the dimeric structure of Al(CH3)3, we can visualize that each aluminum atom is bonded to three methyl groups (CH3). When two Al(CH3)3 units dimerize, they form a structure where the bonding involves three centers (two Al atoms and one C atom from the methyl groups) sharing two electrons. This confirms that the statement is **true**.

### Step 2: Analyze the second statement about B2H6
- **Statement**: B2H6 has three-centered two-electron bonds.
- **Analysis**: In diborane (B2H6), the bonding involves the concept of "banana bonds," where two boron atoms share hydrogen atoms. Each bond can be viewed as a three-centered bond involving two boron atoms and one hydrogen atom, sharing two electrons. Thus, this statement is also **true**.

### Step 3: Analyze the third statement about Lewis acidity
- **Statement**: The Lewis acidity of BCl3 is greater than that of AlCl3.
- **Analysis**: BCl3 is a stronger Lewis acid compared to AlCl3 because boron has an empty p-orbital and can accept electron pairs more readily. In contrast, AlCl3 has a filled p-orbital due to back-bonding from chlorine, which reduces its Lewis acidity. Therefore, this statement is **true**.

### Step 4: Analyze the fourth statement about AlCl4
- **Statement**: AlCl4 is a three-centered two-electron species.
- **Analysis**: AlCl4 involves aluminum bonded to four chlorine atoms. Each chlorine atom has a lone pair and can form dative bonds with aluminum. This results in a structure where there are four electrons involved in bonding, not two. Thus, this statement is **false**.

### Conclusion
Based on the analysis:
- The first, second, and third statements are **true**.
- The fourth statement is **false**.

### Final Answer
The correct statements are:
1. Al(CH3)3 has three-centered two-electron bonds in its dimeric structure. (True)
2. B2H6 has three-centered two-electron bonds. (True)
3. The Lewis acidity of BCl3 is greater than that of AlCl3. (True)
4. AlCl4 is a three-centered two-electron species. (False)