Synthesis and Selected Reactivity Studies of a Dissymmetric (Phosphinoylmethylpyridine N‐Oxide) Methylamine Platform

Abstract

Efficient syntheses for the precursor molecules, 2‐{6‐[((diphenylphosphoryl)methyl)pyridin‐2‐yl]methyl}isoindoline‐1,3‐dione (2), 2‐[(1,3‐dioxoisoindolin‐2‐yl)methyl]‐6‐[(diphenylphosphoryl)methyl]pyridine 1‐oxide (3), and their 6‐[bis(2‐(trifluoromethyl)phenyl)phosphoryl]methyl analogues are reported along with their transformations into the dissymmetric ligands, [(6‐(aminomethyl)pyridin‐2‐yl)methyl]diphenylphosphine oxide (4), 2‐(aminomethyl)‐6‐[(diphenylphosphoryl)methyl]pyridine 1‐oxide (5) and 2‐(aminomethyl)‐6‐{[bis(2‐(trifluoromethyl)phenyl)phosphoryl]methyl}pyridine 1‐oxide (5‐F). Selected reactivity of the aminomethyl substituent of 4 and 5, as well as complexation reactions of several of the compounds with lanthanide(III) ions are described. Molecular structures of three uniquely different complexes, {Pr{2‐[HC(O)N(H)CH2]‐6‐[Ph2P(O)CH2]C5H3NO}(NO3)3(MeOH)}2, {Eu{2‐[(Me2N)2CN(H+)CH2]‐6‐[Ph2P(O)CH2]C5H3N(H)+}(NO3)4(OMe)} and {Er{2‐[(C8H4O2)NCH2]‐6‐[Ph2P(O)CH2]C5H3N(O)}(NO3)3(MeOH)}·(CH3)2CO, have been determined by single‐crystal X‐ray diffraction methods. The observed and computationally modeled structures that employ bidentate and tridentate ligand/metal interactions are compared. These results suggest further ligand modifications that should provide improved solvent extraction reagents.

(Pyrazolyl)-(phosphinoyl)pyridine iron(II), cobalt(II) and nickel(II) complexes: Synthesis, characterization and ethylene oligomerization studies

“…The 31 P ( 1 H) NMR spectrum showed sharp singlet signals at about d À11 ppm as expected for the phosphine ligands L1a and L2a [23,31], and another singlet at around 29 ppm. The signal at 29 ppm was attributed to the oxidized phosphine in L1b and L2b consistent with literature findings for related compounds [32]. Further evidence of this oxidation was illustrated by the gradual increase of the signals at d 29.69 ppm followed by concomitant decrease of the peak at d À11 ppm (Supplementary information, S3).…”

Synthesis and selected lanthanide coordination chemistry of new ((1H-pyrazol-1-yl)methyl)pyridine and -pyridine 1-oxide ligands

“…Subsequent formation of the complex [Eu(4) 3+ ] with a tridentate coordination mode occurs with (G) = 4.78 kcal/mole or 1.59 kcal/mol/donor group. Although the ligand reorganization energy is significantly higher for 4 compared to 2, it is still lower than the value computed for the NOPOPO ligand, I (R = Ph), 8.8 kcal/mol or 2.93 kcal/mol/donor group[45], and it is well known that ligands of type I readily form strong lanthanide complexes utilizing the tridentate binding mode[22][23][24][45][46][47][48][49]. Interestingly, addition of the N-oxide group back into the ligand framework and subsequent formation of the tridentate chelate structure [ Eu(5) 3+ ], as shown inFigure 7b, leads to a decrease in strain free energy, (G) = 3.78 kcal/mol or 1.26 kcal/mol/donor.…”

“…The resulting calculated relative strain free energies (G) per donor group were then compared with data for similar ligand types. The method has been used in the evaluation of a number of other ligand systems[43] including studies of several related NOPO and NOPOPO ligands[22][23][24][44][45][46][47][48]. The energy minimized free ligand conformers for 2, 4 and 5 are shown in Figures 5a, 6a and 7a, respectively.…”