Role of Bis(phosphinimino)methanides as Universal Ligands in the Coordination Sphere of Metals across the Periodic Table

Preparation of polydentate phosphonate-functionalized adsorbent for selective extraction of rare earth ions in harsh acidic solution

Developing adsorbents capable of extracting rare earth element (REE) in harsh acidic solution is a challenging issue in the recycle of REE from secondary resources. In this work, porous polystyrene resin was facile modified with tris(2-aminoethyl)amine followed by methylenebis(phosphonic dichloride) to create a polydentate phosphonate-functionalized adsorbent for this purpose. The adsorption properties of four REE ions (Ce3+, Nd3+, Gd3+, and Dy3+) were investigated in terms of affinity constants, selectivity, and recovery. The adsorption mechanism of adsorbent for REE ions is regarded as the strong chelation interaction provided by the phosphonate ligand, which was verified by the experiments of acid and salt effects, thermodynamic and kinetic analysis. By using the diluted digest solution of a permanent magnet as model of strong acidic sample (1 mol/L HCl), the batch adsorption method generates high recovery ranging from 58.1 to 100% toward five REE ions (Y3+, Ce3+, Nd3+, Gd3+, and Dy3+), while the simulated continuous column bed enhances their total contents from 35.4% in the original digest solution to 88.9% in the eluent. In conclusion, the adsorbent indicates an excellent extraction ability in harsh acidic solution, and the recycle of REE using this adsorbent can predictably reduce alkali consumption to neutralize digest solution of secondary resources and improve greenness in manufacture.

Luminescent Manganese(II) Iminophosphorane Derivatives

The reaction between the iminophosphorane ligand N-phenyl-1,1,1-triphenylphosphanimine (NPh=PPh3) and anhydrous manganese(II) halides allowed the isolation of complexes with the general formula [MnX2(NPh=PPh3)2] (X = Cl, Br, I). The compounds showed luminescence in the green region attributed to the 4T1(4G)→6A1(6S) transition of the metal centre in the tetrahedral field, which was superimposed in the cases of X = Cl and X = Br on weak ligand-centred fluorescence. The emission and excitation spectra were compared with those of the free ligand and of the related zinc(II) bromo-complex. DFT calculations on the free ligand and on the manganese(II) bromo-complex helped to rationalise the experimental data. The protonation of NPh=PPh3 led to the formation of the iminium cation [NHPh=PPh3]+, which was used as a building block for the synthesis of organic-inorganic hybrids with the general formula [NHPh=PPh3]2[MnX4] (X = Cl, Br, I). The crystal structure of [NHPh=PPh3]2[MnBr4] was determined by means of X-ray diffraction. Green photoluminescence associated with the metal-centred transition was also observed for the organic-inorganic hybrids, with higher quantum yields with respect to the neutral [MnX2(NPh=PPh3)2] complexes. In the case of X = I, luminescence from the cation was superimposed on that from the tetraiodomanganate anion upon excitation of the compound with near-UV light.

Electrosynthesis of iminophosphoranes and applications in nickel catalysis

P(v) iminophosphorane compounds are accessed via electrochemical oxidation of commercially available P(iii) phosphines, including mono-, di- and tri-dentate phosphines, as well as chiral phosphines. The reaction uses inexpensive bis(trimethylsilyl)carbodiimide as an efficient and safe aminating reagent. DFT calculations, cyclic voltammetry, and NMR studies provide insight into the reaction mechanism. The proposed mechanism reveals a special case of sequential paired electrolysis. DFT calculations of the frontier orbitals of an iminophosphorane are compared with those of the analogous phosphines and phosphine oxides. X-ray crystallographic studies of the ligands as well as a Ni-coordination complex provide structural insight for these ligands. The utility of these iminophosphoranes as ligands is demonstrated in nickel-catalyzed cross-electrophile couplings including C(sp2)-C(sp3) and C(sp2)-C(sp2) couplings, an electrochemically driven C-N cross-coupling, and a photochemical arylative C(sp3)-H functionalization. In some cases, these new ligands provide improved performance over commonly used sp2-N-based ligands (e.g. 4,4'-di-tert-butyl-2,2'-bipyridine).

Bi- and tridentate coordination behaviour of a novel bis(phosphinimino)methanide ligand

Herein, we report the synthesis of a novel ferrocenyl-functionalized bis(phosphinimino)methane ligand (CH2 (PPh2 NFc)2 ). Deprotonation of CH2 (PPh2 NFc)2 with KN(SiMe3 )2 gave the dimeric species [K{CH(PPh2 NFc)2 }]2 , which was further reacted with ECl2 (E=Ge, Sn) to yield the tetrylene compounds [{CH(PPh2 NFc)2 }ECl]. The ligand and the resulting tetrylenes were examined for their electrochemical properties with the aid of cyclic voltammetry. Furthermore, the reaction of the tetrylenes [{CH(PPh2 NFc)2 }ECl] with [AuC6 F5 (tht)] resulted in the bimetallic complexes [{(AuC6 F5 )CH(PPh2 NFc)2 }ECl] with an unusual Au coordination on the ligand backbone.