Lariat ethers with fluoroaryl side-arms: a study of CF⋯metal cation interaction in the complexes of N-(o-fluoroaryl)azacrown ethers

Abstract

New lariat ethers, N-(o-fluorophenyl)aza-15-crown-5 (F-A15C5) and N,N'-bis(o-fluorophenyl)diaza-18-crown-6 (F(2)-A(2)18C6), were prepared by the N-arylation of the corresponding azacrown ethers. The interaction of the ligands with metal cations was studied in solution by (1)H and (19)F NMR (in acetone-d(6)) and UV spectroscopy (MeOH) confirming the formation of complexes of F(2)-A(2)18C6 with K(+), Na(+), Ag(+), Ba(2+), Pb(2+) and of F-A15C5 with Na(+) and giving evidence of CFmetal cation interaction. Cation binding constants (beta, evaluated by UV titration method), demonstrate that F-A15C5 and F(2)-A(2)18C6 form more stable complexes than their fluorine-free analogs. The effect depends on the nature of the metal cation and is at a maximum for hard, singly charged cations (up to 3 logbeta units for K(+) complex of F(2)-A(2)18C6). The X-ray structures of complexes [Pb(F(2)-A(2)18C6)(H(2)O)](ClO(4))(2) () and [Ba(F(2)-A(2)18C6)(ClO(4))(2)] () reveal short Pb-F (2.805 A) and Ba-F (2.965 A) contacts. Complex is centrosymmetric (C(i)), while complex has C(2) symmetry with one-side coordination of o-fluorophenyl groups to Pb(2+). This "one-side" coordination mode of Pb(2+) is indicative of a partial localization of the Pb(2+) lone pair.

Scorpionate complexes of aza-18-crown-6 containing fluoronitrophenyl substituents as studied by electrospray ionization mass spectrometry

“…Furthermore, additional fluorine atoms at the meta and para positions also decrease the partial negative charge on the fluorine atoms at the ortho position. Therefore, the interaction analogous to that observed by Sazonov et al cannot be expected. And indeed, no higher stability of complexes of 2 – 5 in comparison to the complexes of 1 was observed in this work.…”

“…It should be noted that compounds similar to 1 – 5 have been synthesized by Sozonov et al In contrast to 1 – 5 , the compounds studied by Sazonov did not contain a nitro group. They contained fluorine atoms at the ortho position and the interaction between these atoms and metal cations complexed by a crown ether moiety has been observed . The question is whether an analogous interaction can occur for 2 – 5 , which contain fluorine atoms at the ortho position.…”

“…It has already been shown that a number of aza‐18C6 or aza‐15C5 conjugates are able to coordinate a metal cation in the scorpionate mode; however, not the conjugates with a nitro group . In general, coordination of a metal cation by a nitro group is rather rare and the interaction between the nitro group and the metal cation is usually weak …”

C–F⋯M+ interaction in anionic α-fluorovinyl rhenium oxycarbene complexes and their β-fluoroenolate analogs

“…The sign of the cationinduced 19 F chemical shift (Dd F ) was the first question considered. For different ligands/cations both negative (high filed) [5][6][7] and positive values [5,27] are reported in the literature, allowing one to question the reliability of Dd F as an indicator of CFÁ Á ÁM n+ interaction.…”

Solid state and solution structures of alkaline-earth complexes with lariat ethers containing aniline and benzimidazole pendants

“…The coordination of a methanol molecule (occupation factor 0.819(4)) or a water molecule (occupation factor 0.181(4)) completes seven-coordination around the Mg(II) ion, while the coordination of two methanol molecules results in an eight-coordinate Ca(II) complex. An asymmetrically coordinated bidentate perchlorate anion and a methanol molecule result in the formation of a nine-coordinated Sr(II) complex, and the coordination of two bidentate perchlorate anions gives an 11-coordinate Ba(II) neutral complex [45] . The distances between the metal ions and the tertiary amine nitrogen atoms are considerably longer than those to the nitrogen atoms of the pendant arms.…”