Molecular structures of 4 a (left) and 5 a (right). Thermal ellipsoids pictured at 50 % probability level; hydrogen atoms, with the exception of that bonded to phosphorus in 4 a, omitted for clarity. There are two crystallographically independent molecules of 4 a in the lattice, for clarity, only bond metric data for one of them is provided. Selected interatomic distances [Å] and angles [°]; 4 a: P1−N1 1.720(1), P1−O1 1.688(1), P1−O2 1.681(1), P1−O3 1.588(1), P1−H1 1.30(2), O1‐P1‐O2 151.44(5), O1‐P1‐O3 104.26(5), O1‐P1‐H1 85.5(7), O2‐P1‐O3 104.29(5), O2‐P1‐H1 85.9(7), O3‐P1‐H1 106.5(7), N1‐P1‐O1 88.05(5), N1‐P1‐O2 88.00(5), N1‐P1‐O3 99.39(5), N1‐P1‐H1 154.2(7), C6‐N1‐C20 130.78(10), C6‐N1‐P1 114.31(8), C20‐N1‐P1 114.71(8). 5 a: P1−N1 1.717(1), P1−O1 1.721(1), P1−O2 1.732(1), P1−O3 1.585(1), P1−C33 1.821(2), O1‐P1‐O2 168.15(5), O1‐P1‐O3 96.30(5), O1‐P1‐C33 88.05(5), O2‐P1‐O3 95.52(4), O2‐P1‐C33 89.87(5), O3‐P1‐C33 104.07(5), N1‐P1‐O1 86.74(4), N1‐P1‐O2 86.66(4), N1‐P1‐O3 119.96(5), N1‐P1‐C33 135.96(5), C6‐N1‐C20 128.50(10), C6‐N1‐P1 115.33(8), C20‐N1‐P1 116.06(8).