New organotin(IV)-phosphoramidate complexes: Breaking of the PO⋯HN hydrogen bonds and its influence on the molecular packing

Phosphoryl donor (PO) ligands (tBuNH)3PO (1), (C6H5CH2NH)3PO (2) and (4-NO2–C6H4C(O)NH)(OC4H8N)2PO (3) were used for the preparation of new organotin(IV) complexes Cl2Me2Sn(PO)2 (4–6). The environment at the nitrogen atom in the phosphoramide ligand is almost planar and it does not take part in hydrogen bonding as an acceptor in complexes 4–6, reflecting its low Lewis base character, and the Sn atom is located at the inversion center, making half of the molecule related by symmetry. The Sn coordination geometry is octahedral with the pair of similar ligands in a trans orientation. The crystal structure of 6 demonstrates that the phosphoryl group, and not the carbonyl group, coordinates to the tin center. A blue shift in the NH stretching frequencies of 4 and 6, in comparison to the free ligands 1 and 3, is attributed to vanish of the NH⋯O hydrogen bonds, but the PO stretching frequencies of the complexes exhibit no significant changes with respect to the related ligands because of minor differences caused by forming the PO⋯Sn instead of the PO⋯HN. The NMR experiments indicate an increasing in 2J(P,H) coupling constants in 4 and 6 and 3J(P,C) in 5 compared to the related ligands. The hydrogen bond pattern of the ligands and the complexes were compared.