Interaction of morpholine and thiomorpholine with molecular diiodine. X-ray crystal structure of morpholinium triiodide

ARCA, MASSIMILIANO;F. Cristiani;F. A. Devillanova;A. Garau;ISAIA, FRANCESCO;LIPPOLIS, VITO;G. Verani;F. Demartin

1997-01-01

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Abstract

The reactions between the donors morpholine (1) and thiomorpholine (2) with I2 in low polar solvents (C6H6, CHCl3, CH2Cl2) and different donor/I2 concentration ratios (1:1, 1:2, 1:3) yield solids of stoichiometry 1-I2, 1H+I3 -, 1H+I5 -, 2·I2, and 2H+I3 -. Crystals suitable for X-ray structure determination have been obtained only for 1H+I3 -. All the solids were characterized by FT-Raman and FT-IR spectroscopies in the region of the v(I-I) frequencies. Studies in solution have been carried out on each of the reactions between 1, 2, and N-methyhnorpholine (3) with I2. The formation constants of the 1:1 adducts of 2 and 3 determined at 20°C by UV-visible spectroscopy are 8500 and 8400 dm3 mol-1, respectively. IR spectroscopy shows that I2 binds the nitrogen of 1 and 2 both in axial and equatorial positions. Further, FT-Raman and 13C NMR spectroscopies support the nature of weak adducts between 1 (2) and the molecular diiodine in solution.