ALBERT

Description: Syntheses for 2-[1-(diarylphosphinoyl)-1-(pyridin-2-yl)methyl]pyridines, ( 8a, b ), and 2-[1-(diarylphosphinoyl)-1,1-bis(methylpyridin-2yl)methyl]pyridines, ( 11a, b ), (Ar = C 6 H 5 and 2-CF 3 C 6 H 4 ), based on substitution of 2-methylpyridine fragments onto the exo methylene carbon atom of 2-[(diaryl)phosphinoylmethyl]pyridine platforms, are described. N-oxidations of 8a, b and 11a, b produced the 2-[1-(diarylphosphinoyl)-1-(1-oxy-pyridin-2yl)methyl]pyridine N -oxides ( 5a, b ) and the 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridines ( 6a, b ), respectively. The “short-arm“ pyridine fragment of 11a, b resists N-oxidation, and the fully oxidized molecules, 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridine N -oxides ( 7a, b ) were not isolated. Molecular mechanics calculations for gas phase 1:1 ligand/lanthanide complexes indicated that 5a should accommodate a tridentate NO(meNO)PO coordination mode with minimal steric strain. In contrast, 7a cannot form tetradentate NO(meNO) 2 PO chelates; however, tridentate binding should be accessible with minimal ligand strain. Coordination complexes of 8a, b , 5a, b , 6a, b and 11a, b with Ln(NO 3 ) 3 salts were isolated and a X-ray crystal structure for [Er( 8a )(NO 3 ) 3 (MeOH) 2 ]·CH 2 Cl 2 , revealed a monodentate Er–O=P interaction. On the other hand, complexes formed by a more symmetrical trifunctional phenylphosphino-bis-2-methylpyridine N, N, P-trioxide ligand, (meNO) 2 PO* , {La[( meNO) 2 PO* )](OTf) 2 (MeOH) 3 (H 2 O) + }(OTf – ) and {Pr[ (meNO) 2 PO* )](OTf)(MeOH) 4 + }(OTf – ) 2 , realized a tridentate coordination mode. Solvent extraction behaviors for Eu III and Am III in nitric acid solutions using 5a, b , 6a, b , Ph 3 PO and the parent bifunctional ligand 2-[(diphenylphosphanyl)methyl]pyridine N, P-dioxide ( 3a ) in 1, 2-dichloroethane were assessed, and 5a, b and 6a, b were found to behave more like Ph 3 PO than 3a .