The coordination chemistry of fluorocarbons: Group-I and group-II metal ion complexes of fluoro macrocycles

Two new fluoro macrocycles BenzoFN(2)O(3) and F(N2O2)(2)C2H4 were synthesized in the reactions of 1,3-bis(bromomethyl)-2fluorobenzene with benzo-diaza-15-crown-5 and 1,2-bis(diaza-12-crown-4)ethane, respectively, in 30% yield each. Close CF...metal ion interactions in the respective alkaline metal complexes in solution are evidenced by characteristic shifts of the F-19-NMR resonances of up to delta = 18.7 relative to the free ligand and by a decrease of the (1)J(CF) coupling constant of up to 20 Hz, which is most pronounced in BenzoFN(2)O(3) . Li+ and F(N2O2)(2)C2H4 . K+. In BenzoFN(2)O(3) . Li+ a (1)J(F-19-Li-7) of 15.5 Hz was observed, which is indicative of very close CF...Li+ interactions in solution. In the X-ray crystal structures of BenzoFN(2)O(3) . Na+ [CF...Na+ 246.8(2) pm], 26-fluoro-4,7,13, 16-tetraoxa-1, 10-diazatricyclo[8.8.7.1(20,24)]-hexacosa-20,22,24 (26)triene . Na+ {CF...Na+ 267.1(2) pm} and 21-fluoro-3,6,9,12,15,18-hexaoxabicyclo[18.3.1(1,20)]henei-cosa -1(24),20,22-triene . Ba2+ [CF...Ba2+ 299.0(3) pm] short CF...metal interactions were found. Such close CF...metal ion interactions do not result in a lengthening of the C-F bonds, which is not a sign of weak CF...metal ion interactions, since a Cambridge Structural Database search revealed that a shortening of the C-O bond length is also not observed in crown ether complexes of alkaline metals.