1. Research Institute of Comprehensive Energy Industry Technology College of Chemistry & Chemical Engineering Yan'an University Yan'an Shaanxi 716000 P. R. China
2. Key Laboratory of Applied Surface and Colloid Chemistry Ministry of Education Xi'an Key Laboratory of Organometallic Material Chemistry School of Chemistry & Chemical Engineering Shaanxi Normal University Xi'an 710119 P. R. China
3. School of Chemistry & Chemical Engineering Xinjiang Normal University Urumqi 830054 P. R. China
4. Institut für Anorganische Chemie Eberhard Karls Universität Tübingen 72076 Tübingen Germany