ISSN:
0009-2940
Keywords:
Difluorometacyclophanes
;
syn-Metacyclophanes
;
Through-space F,F spin coupling
;
X-ray structures
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The close approach of the fluorine nuclei in the difluorinated syn-[3.3]metacyclophanes 1, 2 and their [2.2] analogues 3, 4 leads to strong 19F,19F spin-spin interactions which obey a through-space mechanism. The geometries of 1-4 were estimated by MM2 molecular mechanics computations, those of 1 and 3 were also determined by X-ray structural analyses. The decrease of the F,F internuclear distance in the series 1, 2, 3, 4 (2.78-2.48 Å) correlates with an increase of J(FF) from +42.1 to +99.2 Hz. It follows that, for a given distance d(FF), J(FF) is up to twice as large as a previous empirical correlation has assumed and even larger with respect to earlier theoretical calculations. Only weak F,F spin interaction occurs in 8, the anti isomer of 4.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19941270623
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