Let’s **summarize the key quantitative physicochemical properties** directly from your data and use these for meaningful classification.  
To maximize quantitative rigor, we will **consolidate the data into a matrix**, then classify the compounds based on physicochemical metrics that most effectively differentiate this set.

### **Step 1: Extract Key Quantitative Properties**
Properties available for all ligands:
- **Molecular Weight** (g/mol)
- **XLogP** (partition coefficient, hydrophobicity)
- **TPSA** (Topological Polar Surface Area, Å²)
- **H-bond acceptors/donors**
- **Rotatable Bond Count**

**Tabulation:**

| Ligand                                                       | MW     | XLogP | TPSA  | HBA | HBD | Rot. Bonds |
|--------------------------------------------------------------|--------|-------|-------|-----|-----|------------|
| bis(1-adamantyl)-[3,6-dimethoxy-...phosphane                 | 640.9  | 11.8  | 18.5  | 2   | 0   | 9          |
| dicyclohexyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosph  | 476.7  | 10.1  | 0     | 0   | 0   | 7          |
| ditert-butyl-[2-[2,4,6-tri(propan-2-yl)phenyl]phenyl]phosph  | 424.6  | 8.5   | 0     | 0   | 0   | 7          |
| ditert-butyl-[3,6-dimethoxy-2-...phosphane                   | 484.7  | 8.4   | 18.5  | 2   | 0   | 9          |

<br/>

---

### **Step 2: Choose Most Differentiating Quantitative Properties**
Given the low number of H-bond donors (always zero), we discard that.
- **XLogP (>8 for all, but with clear grouping above/below 10)**
- **TPSA (0 vs. 18.5)**
- **H-bond Acceptors (0 or 2)**
- **Rotatable Bonds (not strongly differentiating in this small set)**

**Obvious bifurcation is by TPSA and XLogP/HBA count:**
- **TPSA = 18.5; H-bond acceptor = 2**: Only the *dimethoxy* ligands.
- **TPSA = 0; H-bond acceptor = 0**: The others (no methoxy groups).

<br/>

---

### **Step 3: Classification**

#### **Class 1: Dimethoxy-ligands**
- *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*

  **Quantitative Criteria:**  
    - TPSA = 18.5 Å²  
    - H-bond acceptor count = 2

#### **Class 2: Non-methoxy analogues**
- *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*

  **Quantitative Criteria:**  
    - TPSA = 0  
    - H-bond acceptor count = 0

#### **No further meaningful splitting** can be justified by other values (e.g., XLogP splits, MW) because **the largest difference is functional group/polar surface area-based**.

---

## **Final Classification Table**
| Class       | Ligands                                                                                                                                             | Quantitative Defining Properties           |
|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------|
| 1: Dimethoxy| bis(1-adamantyl)-(3,6-dimethoxy-…phosphane), ditert-butyl-(3,6-dimethoxy-…phosphane)                                                                | TPSA = 18.5, HBA = 2                      |
| 2: Non-methoxy| dicyclohexyl-(2-…phenyl…phosphane), ditert-butyl-(2-…phenyl…phosphane)                                                                          | TPSA = 0, HBA = 0                         |

### **Summary/Justification**
- The *only major physicochemical separation is the presence/absence of 3,6-dimethoxy groups*, which increases TPSA and HBA.
- XLogP, MW, or rotatable bonds split by bulk/size but **not dramatically enough to justify more classes given the set** (all very hydrophobic/high MW).

**No further meaningful divisions are supported by the quantitative data.**

---

### **If you need this restated for another set of categories or further broken down:**  
Please specify, but the above reflects the database-driven, property-based grouping strictly per your instructions.