[1] Tech Univ Carolo Wilhelmina Braunschweig, Inst Organ Chem, D-38106 Braunschweig, Germany
[2] Tech Univ Carolo Wilhelmina Braunschweig, NMR Lab Chem Inst, D-38106 Braunschweig, Germany
[3] Tech Univ Carolo Wilhelmina Braunschweig, Inst Anorgan & Analyt Chem, D-38023 Braunschweig, Germany
[4] Univ Oregon, Dept Chem, Eugene, OR 97403 USA