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Coordination Chemistry with CF Units as σ Donors: Ag + Complexes of Partially Fluorinated Crown Ethers with Direct Metal–Fluorine Interactions
Author(s) -
Plenio Herbert,
Diodone Ralph
Publication year - 1996
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19961291012
Subject(s) - chemistry , cryptand , crystallography , fluorine , fluorobenzene , metal , crystal structure , nmr spectra database , stereochemistry , nuclear magnetic resonance spectroscopy , synthon , spectral line , ion , organic chemistry , physics , astronomy , benzene
The partially fluorinated cryptands FN 2 O 4 and BenzoFN 2 O 4 , which are relatives of the [2.2.1]cryptand, were synthesized in good yields from 1,3‐bis(bromomethyl)‐2‐fluorobenzene and diaza‐18‐crown‐6 or benzodiaza‐18‐crown‐6, respectively. These macrobicyclic ligands form very stable complexes with Ag(I) salts, and it was shown that close fluorinesilver interactions occur in solution as well as in the solid state. Numerous experimental evidence for this is available: NMR competition experiments show that Ag + complexes of FN 2 O 4 are significantly more stable than those of HN 2 O 4 (the two ligands are identical except that one fluorine atom is replaced by one hydrogen atom in HN 2 O 4 ); the 1 J CF coupling constants of Ag + · FN 2 O 4 and Ag + · BenzoFN 2 O 4 are reduced by 10 Hz compared to those of the respective free ligands FN 2 O 4 ( 1 J CF =253 Hz) and BenzoFN 2 O 4 . ( 1 J CF =252 Hz). The X‐ray crystal structure of Ag + · FN 2 O 4 revelas short Ag + –F distances [271.4(3) pm]; coupling of the 107,109 Ag + and 19 F nuclei is observed in the 19 F‐NMR spectra ( J =24 Hz for Ag + · FN 2 O 4 , J =25 Hz for Ag + · BenzoFN 2 O 4 ). The 1 H‐NMR spectrum of Ag + · FN 2 O 4 is very complex and exhibits sixteen unique proton resonances, whose evaluation yielded coupling constants and NOEs, which show that the structure in solution is compatible with the results obtained by the X‐ray crystal structure determination.