1. Institute of Organic Chemistry; Technical University of Braunschweig; Hagenring 30 38106 Braunschweig Germany
2. Department of Chemistry; Al.I. Cuza University of Iasi; 11 Carol I 700506 Iasi Romania
3. Institute of Inorganic and Analytical Chemistry; Technical University of Braunschweig; Hagenring 30 38106 Braunschweig Germany