Attempts to form extended supramolecular structures incorporating hafnium(IV) complexes of p-sulfonatocalixarene resulted in the serendipitous formation of two polynuclear-hafnium clusters. Subsequent reaction between hafnium triflate and 1 M sulfuric or p-toluenesulfonic acid solutions also led to the formation of the same clusters, identified as cations based on Hf-17 and Hf-4, respectively. (c) 2006 Elsevier B.V. All rights reserved.
Dalgarno, S. J., Atwood, J. L., & Raston, C. L. (2007). The synthesis and structural characterisation of two polynuclear hafnium(IV) complexes. Inorganica Chimica Acta, 360(4), 1344-1348. https://doi.org/10.1016/j.ica.2006.03.018