Read the passage given below and answer the following questions:
In spite of the predictions of stable noble gas compounds since at least 1902, unsuccessful attempts at their synthesis gave rise to the widely held opinion that noble gases are not only noble but also inert. It was not until 1962 that this dogma was shattered when Bartlett in Canada published the first stable noble gas compound `XePtF_(6)` . This discovery triggered a worldwide frenzy in this area, and within a short time span many new xenon, radon, and krypton compounds were prepared and characterized. The recent discoveries show the ability of xenon to act as a ligand . The discovery by Seppelt’s group that more than one xenon atom can attach itself to a metal center which in the case of gold leads to surprisingly stable Au- Xe bonds. The bonding in `[AuXe_(4)]^(2+)` involves 4 Xe ligands attached by relatively strong bonds to a single Au(II) center in a square planar arrangement with a Xe-Au bond length of about 274 pm This discovery provides not only the first example of multiple xenon ligands but also represents the first strong metal - xenon bond.
(Source: Christe, K. O. (2001). A renaissance in noble gas chemistry. Angewandte Chemie International Edition, 40(8), 1419-1421.)
In the complex ion `[AuXe_(4)]^(2+)`, Xe acts as :

Options

A. central atom
B. ligand
C. chelating agent
D. electrophile

Answer

To determine the role of xenon (Xe) in the complex ion \([AuXe_4]^{2+}\), we will analyze the information provided in the passage step by step.

### Step-by-Step Solution:

1. **Understanding the Complex Ion**: The complex ion given is \([AuXe_4]^{2+}\). Here, Au represents gold, and Xe represents xenon. The notation indicates that there are four xenon atoms coordinated to a single gold ion.

2. **Role of Ligands**: In coordination chemistry, ligands are ions or molecules that can donate a pair of electrons to a central metal atom or ion to form a coordination complex. They can be classified as monodentate (binding through one site) or polydentate (binding through multiple sites).

3. **Xenon as a Ligand**: According to the passage, xenon has been shown to act as a ligand. This is a significant finding since noble gases were traditionally considered inert. The passage specifically mentions that multiple xenon atoms can attach to a metal center, indicating that xenon can form bonds with metals.

4. **Bonding in \([AuXe_4]^{2+}\)**: The passage states that in the complex, there are four xenon ligands attached to a single Au(II) center. The bonding is described as relatively strong, which supports the idea that xenon is functioning as a ligand in this complex.

5. **Geometry of the Complex**: The arrangement of the ligands around the metal center is square planar, which is typical for certain metal complexes, especially those involving d8 metal ions like Au(II).

6. **Conclusion**: Based on the information provided, we can conclude that in the complex ion \([AuXe_4]^{2+}\), xenon acts as a ligand. It is not a chelating reagent (which would involve binding through multiple sites on the same ligand), nor is it an electrophile (which would accept electrons), and it is not the central atom (which is gold in this case).

### Final Answer:
In the complex ion \([AuXe_4]^{2+}\), Xe acts as a ligand.