Synthesis and Lanthanide Coordination Chemistry of Phosphine Oxide Decorated Dibenzothiophene and Dibenzothiophene Sulfone Platforms

Abstract

Syntheses for new ligands based upon dibenzothiophene and dibenzothiophene sulfone platforms, decorated with phosphine oxide and methylphosphine oxide donor groups, are described. Coordination chemistry of 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene (8), 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene-5,5-dioxide (9) and 4,6-bis(diphenylphosphinoyl)dibenzothiophene-5,5-dioxide (10) with lanthanide nitrates, Ln(NO3)3·(H2O)n is outlined, and crystal structure determinations reveal a range of chelation interactions on Ln(III) ions. The nitric acid dependence of the solvent extraction performance of 9 and 10 in 1,2-dichloroethane for Eu(III) and Am(III) is described and compared against the extraction behavior of related dibenzofuran ligands (2, 3; R = Ph) and n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (4) measured under identical conditions.

Lanthanide phosphine oxide complexes

“…The structure of the erbium nitrate complex of (36, X = O), [Er(NO 3 ) 2 (36) 2 ](NO 3 ) as a methanol solvate shows the metal to be 8-coordinate with the furan oxygen atom not bonded to the metal despite computational analysis suggesting that there would be relatively little strain energy involved in it doing so [103]. With X = SO 2 (36) (37)]Á 2MeCN with the reduced coordination number in the erbium complex being a consequence of the lanthanide contraction [104]. The 31 P NMR spectra of the La complex indicate that a dynamic equilibrium exists between free ligand and complexes of (36) and (37) in methanol.…”

Synthesis and lanthanide coordination chemistry of CMPO-decorated dibenzothiophene and dibenzothiophene sulfone platforms

“…Following combination of the reagents, a clear, pale yellow solution was obtained that was heated (85 °C, 2 h) and stirred. The resulting dark red solution was cooled (0 °C), transferred dropwise over 1h into a vigorously stirred solution of 4,6bis(chloromethyl)dibenzothiophene (1) [35] (1.40 g, 4.98 mmol) in toluene (50 mL, 0 °C), and the combination was then heated (85 °C) and stirred (12 h). The resulting mixture was cooled, diluted with CH 2 Cl 2 (150 mL), and the organic phase washed with brine (2 x 30 mL) and water (3 x 30 mL).…”

“…However, in one case, the slow (5 weeks) evaporation of a solution of the nominal complex [Eu(2)(NO 3 ) 3 ],dissolved in a mixture of MeOH and i-PrOH (2:1), provided suitable single crystals for which a structure determination was accomplished. A view of the structure is shown in Figure 5, and selected bond lengths are listed in Table 2 [35]. There are also six O-atoms from three asymmetrically bonded nitrate anions in the inner coordination sphere.…”

“…Primarily in support of efforts to develop efficient, selective recognition reagents and separation processes for hard f-element ions present in nuclear waste solutions, parallel efforts to prepare appropriately preorganized harder donor group-decorated assemblies have taken place, and much of that work has been reviewed [27][28][29][30][31][32][33]. Relevant to those activities and to the present contribution, syntheses for trifunctional hybrid ligands of types C-E, that combine the A and B platforms with phosphine oxide donor groups, have also recently been reported [34,35] along with studies of their coordination chemistry with trivalent lanthanides. With these hard ions, both C and D are observed to form only bidentate O P O P chelate structures in which the soft, weakly basic furan-O and thiophene-S donor sites remain coordination silent.…”

“…In addition, 2, 3 and I show much larger D values than the CMPO ligand G at all acid strengths.It is also apparent that the variations in D values for 2, 3 and I are very similar suggesting that the DBT and pyridine N-oxide platform donor groups may not be strongly influencing the extraction thermodynamics beyond serving to assemble the two CMPO fragments in a favorable geometric condition suitable for effective metal ion binding in DCE solution. It is also pointed out that 2, 3 and I are superior extractants compared to the bis-(methylphosphine oxide) compounds C-E[34,35]. Extractions with samples of meso-2 and meso-3 were also performed, and the plots D vs [HNO 3 ] are provided in the Supplementary Data.…”