A CSD analysis on H-bond patterns from phosphoric triamides to their coordination compounds, new complexes with (tBuNH)3PO ligand (PO): Cl2Ph2Sn(PO)2 and Fe(PO)2(NO3)3

Investigating Metal-Tributyl Phosphate Complexes during Supercritical Fluid Extraction of the NdFeB Magnet Using Density Functional Theory and X-ray Absorption Spectroscopy

Supercritical fluid extraction (SCFE) is gaining significant interest as a green technology for the recycling of end-of-life waste electrical and electronic equipment (WEEE). Neodymium iron boron (NdFeB) magnets, which contain large quantities of critical rare-earth elements such as neodymium, praseodymium, and dysprosium, are widely used in wind turbines and electric/hybrid vehicles. Hence, they are considered a promising secondary resource for these elements when they reach their end-of-life. Previously, the SCFE process was developed for recycling WEEE, including NdFeB; however, the process mechanism remains unexplored. Here, density functional theory, followed by extended X-ray absorption fine structure and X-ray absorption near-edge structure analyses, are utilized to determine the structural coordination and interatomic interactions of complexes formed during the SCFE of the NdFeB magnet. The results indicate that Fe(II), Fe(III), and Nd(III) form Fe(NO₃)₂(TBP)₂, Fe(NO₃)₃(TBP)₂, and Nd(NO₃)₃(TBP)₃ complexes, respectively. This theory-guided investigation elucidates the complexation chemistry and mechanism during the SCFE process by rigorously determining the structural models.

The first coordination polymers with an [O]2[N]P(S)-Hg segment: a combined experimental, theoretical and database study

The study of one-dimensional coordination polymers {Hg₂Cl₄L₁}_n (1), {HgBr₂L₁}_n (2) and {Hg₂Cl₄L₂}_n (3) (L₁ = (S)P(OC₂H₅)₂NHC₆H₄NHP(S)(OC₂H₅)₂ and L₂ = (S)P(OC₂H₅)₂NC₄H₈NP(S)(OC₂H₅)₂) is the first such structural study of Hg(ii) coordination polymers with (O)₂(N)PS-based ligands. The mercury atoms adopt a distorted trigonal pyramidal environment, Hg(Cl)₃(S) for 1 and 3 and Hg(Br)₂(S)₂ for 2, and the difference observed in the stoichiometry of mercury halide to the thiophosphoramide ligand in 1 and 3 with respect to the one in 2 is a result of the formation of the Hg₂Cl₂ ring, however, the molar ratio 2 : 1 of HgX₂ (X = Cl and Br) to ligand was used for the preparation of all three complexes. The strengths of mercury-sulfur and mercury-halide covalent bonds are evaluated by theoretical calculations (QTAIM and NBO) which show their principally electrostatic nature with a partial covalent contribution. The energies of interactions building supramolecular assemblies and intramolecular interactions, i.e. NHCl, NHBr, CHCl, CHBr, CHO, CHS and CHπ, are theoretically evaluated. The characteristic structural features arising from the aromatic/aliphatic linkers in the ligands and chloride/bromide attached to mercury are investigated by Hirshfeld surface analysis and fingerprint plots.