Let's proceed step-by-step according to your instructions:

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## 1. **Compile and Summarize Quantitative Physicochemical Properties**

I'll extract the major quantitative physicochemical properties provided for each ligand from the supplied PubChem data:

| Ligand Name                                                                 | MW (g/mol) | XLogP | TPSA  | H-Bond Donor | H-Bond Acceptor | Rotatable Bonds |  
|------------------------------------------------------------------------------|------------|-------|-------|--------------|-----------------|-----------------|
| bis(1-adamantyl)-[3,6-dimethoxy-2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane | 640.9      | 11.8  | 18.5  | 0            | 2               | 9               |  
| dicyclohexyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane               | 476.7      | 10.1  | 0     | 0            | 0               | 7               |  
| ditert-butyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane               | 424.6      | 8.5   | 0     | 0            | 0               | 7               |  
| ditert-butyl-[3,6-dimethoxy-2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane | 484.7      | 8.4   | 18.5  | 0            | 2               | 9               |  

**XLogP:** measure of hydrophobicity/lipophilicity  
**TPSA (Topological Polar Surface Area):** proxy for ability to form H-bonds and overall polarity  
**H-bond donor/acceptor:** ability to participate in hydrogen-bonding  
**MW:** molecular weight; influences solubility and volatility

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## 2. **Determination of Classification Criteria**

Given the data, the most distinct, quantifiable dividing properties are:
- **TPSA** (0 vs 18.5): reflects the presence/absence of polar groups (specifically methoxy: -OCH₃)
- **XLogP** (hydrophobicity): ranges high for all, but shows a modest spread (8.4–11.8)
- **H-bond Acceptor Count:** directly correlates with TPSA, split as 0/2

The **presence of methoxy substituents** (as deduced from both TPSA>0 and acceptor count=2) provides a clear, quantitative criterion, corroborated by names.

Versions with "3,6-dimethoxy" have higher TPSA (18.5) and 2 H-bond acceptors.  
Others have TPSA = 0, acceptor = 0.

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## 3. **Classification (No More Than Three Groups or All in One if Justified)**

### **Group 1: Ligands with Dimethoxy Substitution (Polar Functionality)**
- **bis(1-adamantyl)-[3,6-dimethoxy-2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane**
- **ditert-butyl-[3,6-dimethoxy-2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane**

**Justification:**  
- Both have TPSA 18.5 and 2 H-bond acceptors (quantitative data)
- Both feature "3,6-dimethoxy" substitution in name

### **Group 2: Ligands Without Dimethoxy (Non-polar Functionality)**
- **dicyclohexyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane**
- **ditert-butyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane**

**Justification:**  
- Both have TPSA 0 and 0 H-bond acceptors (quantitative data)
- Both **lack** "3,6-dimethoxy" in name

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## 4. **Ambiguity/Tie-Breaking**
- **Lipophilicity (XLogP):** All are highly hydrophobic (XLogP>8), so cannot meaningfully use this property for further split.
- **Molecular weight/rotatable bonds:** These vary but not in a way that would justify an additional grouping.

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## 5. **Final Classification Table**

| Group | Ligands                                                                                                    | Common Quantitative Properties                      |
|-------|-----------------------------------------------------------------------------------------------------------|-----------------------------------------------------|
| 1     | bis(1-adamantyl)-[3,6-dimethoxy-...], ditert-butyl-[3,6-dimethoxy-...]phosphane                           | TPSA=18.5, Acceptor=2, XLogP=8.4–11.8, MW=484.7–640.9 |
| 2     | dicyclohexyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane,<br>ditert-butyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosphane | TPSA=0, Acceptor=0, XLogP=8.4–10.1, MW=424.6–476.7    |

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**Summary:**  
### The four ligands are best divided quantitatively into two groups:
- Those with methoxy groups (higher polarity, TPSA/acceptor > 0)
- Those without (very low polarity, TPSA/acceptor = 0).

*No clear, justified data-based reason to form more than two or a single group.*

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Would you like further discussion on specialization within these groups, or additional property breakdowns (e.g., by MW)?