Fig. 1. Molecular structures of 10 (left), 17 (middle) and 28 (right) (ellipsoids at 30% probability and H atoms partially omitted for clarity). Selected bond distances [Å] for 10: C1–C2 1.694(4), B4–C20 1.569(4), B5–C28 1.578(4), C1–C13 1.530(4), and C13–N1 1.448(4). For 17: C1–C2 1.698(2), B4–C20 1.586(3), B5–C26 1.586(2), C1–C13 1.537(2), and C13–N1 1.441(2). For 28: C1–C2 1.743(3), B4–C18 1.585(3), B5–C24 1.583(3), C1–C13 1.530(3), and C13–N1 1.459(3).