Selected bond lengths (Å) and angles (°) of 2-phospha-1,3-butadienes (3a and 3b), radical cations (4a and 4b) and dication salts (5a and 5b).
| 3a | 3b | 4a | 4b | 5a | 5b | |
|---|---|---|---|---|---|---|
| C1–C2 | 1.386(1) | 1.384(2) | 1.432(2) | 1.433(2) | 1.479(3) | 1.478(2) |
| C2–P1 | 1.818(1) | 1.820(1) | 1.758(2) | 1.761(2) | 1.692(2) | 1.692(2) |
| P1–C3 | 1.735(1) | 1.735(1) | 1.785(2) | 1.790(2) | 1.865(2) | 1.853(2) |
| C1–N1 | 1.401(1) | 1.403(1) | 1.375(2) | 1.375(2) | 1.351(3) | 1.344(2) |
| C1–N2 | 1.408(1) | 1.412(1) | 1.382(2) | 1.385(2) | 1.355(3) | 1.356(2) |
| C3–N3 | 1.387(1) | 1.388(1) | 1.349(2) | 1.349(2) | 1.295(3) | 1.295(3) |
| C1–C2–P1 | 117.7(1) | 118.0(1) | 117.3(1) | 117.4(1) | 114.9(1) | 115.3(1) |
| C2–P1–C3 | 109.7(1) | 110.9(1) | 108.8(1) | 110.3(1) | 106.1(1) | 105.2(1) |
| P1–C3–N3 | 117.6(1) | 116.4(1) | 116.0(1) | 115.1(1) | 118.1(2) | 121.5(1) |
| N1–C1–N2 | 103.0(1) | 103.3(1) | 104.8(1) | 104.9(1) | 107.2(2) | 107.3(2) |