Consider the following statement(s) in the context of organometallic complex (X):

A. The carbene ligand donates two electrons to the metal and accepts d electrons to make a π-bond

B. The C (carbene) is nucleophilic

C. Rotation around the Cr=C(OMe)Me double bond has low barrier (< 10 kcal/mol)

Correct statement(s) is/are:

Concept:

The given organometallic compound is type of carbene. There are two types of carbene:

1. Fischer carbene; (CO)₅M=C(OMe)R
2. Schrock carbene; L_nM=C

So the given organometallic compound is a type of Fischer carbene

Explanation:

• Fischer carbene is singlet and electrophilic in nature
• It generally obeys 18e^- rule
• It is two electron donor
• Metal is present in the low oxidation state as compare to the Schrock carbene
• Metal is electron rich and therefore carbene is electron deficient

• Carbene carbon should have at least one Z type group (OR, SH, SR, NH₂)
• Actual structure of Fischer carbene lies between the above two resonating structure and there is partial double bond
• Due to the this resonating structure, rational barrier across the metal and carbene carbon is low because there is no complete double bond present
• From the above explanation it is clear that Fischer carbene is two electron donor, therefore statement A is correct.
• However statement B is wrong as it is electrophilic and the rotational barrier across double bond is low so statement C is also correct.

Conclusion:

Hence, the correct statements are A and C and therefore the correct answer is option 3.