1. Regional Laboratory of Physicochemical Analysis and Structural Research, Jagiellonian University, Karasia 3, PL‐30‐060 Krakow, Poland
2. Department of Organic Chemistry, Jagiellonian University, Karasia 3, PL‐30‐060 Krakow, Poland
3. Lehrstuhl für Strukturchemie der Universität Bochum, Postfach 102148, W‐4630 Bochum, F.R.G.