Hybrid Metallacoronates or One-Dimensional Oxo-Bridged Metal Strings by Self-Assembly—Coordination Number Controlled Product Formation Chelate Complexes, Part 20. This work was supported by the Deutsche Forschungsgemeinschaft (Sa 276/25-1, SFB 583, GK 312), the Bayerisches Langzeitprogramm Neue Werkstoffe and the Fonds der Chemischen Industrie. N.M. gratefully acknowledges a Studienstiftung des deutschen Volkes fellowship. We are also indebted to C. Zapf for his pioneering work documented in his diploma thesis. Part 19: R. W. Saalfrank, H. Glaser, B. Demleitner, F. Hampel, M. M. Chowdhry, V. Schünemann, A. X. Trautwein, Gavin B. M. Vaughan, R. Yeh, A. V. Davis, K. N. Raymond, Chem. Eur. J. 2002, 8, 493–497.