Supramolecular motifs formed by CH3/Cl-substituted arene groups: evidence for structural differences in thiophosphoramides and similarities in their complexes†

Abstract

Differences/similarities of supramolecular motifs are discussed in two new thiophosphoramide structures and their Ni molecular complexes: (C₂H₅O)₂P(S)(NHC(S)NHCH₂C₆H₄X) and [{(C₂H₅O)₂P(S)(NC(S)NHCH₂C₆H₄X)}₂Ni] (X = Cl/CH₃ I/II and III/IV). The structures have equal numbers of donor/acceptor sites contributing to classical hydrogen bonds (PS/CS and 2 × NH in ligands and 2 × PS and 2 × NH in the complexes). However, these donor and acceptor sites contribute to inter/intramolecular hydrogen bonding in ligands and intramolecular hydrogen bonding in complexes. In the supramolecular assemblies of the ligands, the classic hydrogen bonds (N–H⋯SC) are restricted in dimer synthons, and the weaker interactions (formed by Cl/CH₃ substituents) compete against each other. In the complexes, despite the lack of classic intermolecular hydrogen bond, numerous weak interactions, e.g., C–H⋯Y (Y = S, O, Ni, N, and π), contribute to the molecular assemblies, which do not include the participation of Cl/CH₃. Thus, different packing features of ligands, but similar in complexes are observed. Each ligand and the associated complex show nearly equal supramolecular motifs in the slice of the substituted benzyl groups, related to the formation of C–H⋯Cl/π⋯π for the 4-Cl-C₆H₄CH₂ groups in I/III and C–H⋯π for the 4-CH₃-C₆H₄CH₂ groups in II/IV. The repeatabilities of the motifs made by 4-Cl-C₆H₄CH₂/4-CH₃-C₆H₄CH₂ were checked by surveying 142/844 structures with 178/1482 segments in the CSD, which show that 17% and 12% of the structures exhibited similarities with the title structures. The methods X-ray crystallography, 2D fingerprint plots, electrostatic potential surfaces, QTAIM, and energy framework calculations were applied to present the discussion.