Animated Solution for Chemistry - Coordination Compounds: In the complex acetylbromidodicarbonylbis(triethylphosphine)iron(II), the number of Fe–C bond(s) is-

When you first encounter a name like acetylbromidodicarbonylbis(triethylphosphine)iron(II), it can feel like reading a foreign language. But in chemistry, IUPAC names are not just random strings of letters; they are precise architectural blueprints. They tell you exactly what building blocks are present and how they are assembled around a central anchor.

In this problem, our central anchor is the iron atom, denoted by Iron(II). The Roman numeral (II) indicates that iron is in a $+2$ oxidation state. This central metal acts as the core of our complex, ready to accept electron pairs from surrounding molecules or ions, which we call ligands.

To find the number of $Fe-C$ bonds, we need to carefully inspect each ligand attached to the iron center and identify its donor atom—the specific atom that directly shares its electrons with the iron.

Let's break down the ligands one by one:

1. Acetyl: The acetyl group is an organometallic ligand with the formula $C{H}_{3}C{O}^{-}$. In this group, the acyl carbon atom acts as a carbanion and bonds directly to the metal center. This gives us our first direct $Fe-C$ bond.

2. Bromido: This is simply a bromide ion ($B{r}^{-}$). It bonds to the iron through the bromine atom, forming an $Fe-Br$ bond. Since there is no carbon involved in this linkage, it contributes zero $Fe-C$ bonds.

3. Dicarbonyl: The prefix 'di' means two, and 'carbonyl' refers to the carbon monoxide ($CO$) molecule. In a carbonyl ligand, the carbon atom has a lone pair of electrons and is less electronegative than oxygen, making it an excellent electron donor. Because there are two carbonyl ligands, they form two direct $Fe-C$ bonds.

4. Bis(triethylphosphine): The prefix 'bis' indicates two of these bulky ligands. Triethylphosphine has the formula $P(C_2{H}_5{)}_3$. While it contains many carbon atoms in its ethyl groups, the actual donor atom that coordinates with the iron is phosphorus ($P$). Therefore, these ligands form $Fe-P$ bonds, not $Fe-C$ bonds.

Now that we have analyzed the entire blueprint, the final calculation is straightforward. We simply sum up the carbon donors we identified:

- $1$ bond from the acetyl ligand. - $2$ bonds from the dicarbonyl ligands.

Total $Fe-C$ bonds = $1+2=3$.

If you were to visualize this molecule in 3D space, you would see an octahedral geometry. The central iron atom is surrounded by six ligands (1 acetyl, 1 bromido, 2 carbonyls, and 2 phosphines). These ligands arrange themselves symmetrically to minimize electronic repulsion, creating a beautiful and highly structured molecular architecture. Understanding this structure not only helps in answering the question but also gives you a deeper appreciation for the elegance of coordination chemistry.