Are extended structures based on building block viable?

Molecules containing Planar Tetracoordinate Carbon (PTC) are of great interest. C 5 2 - seems to be the simplest species which include a PTC. In this regard, Hoffmann, Vela and coworkers (P.D. Pancharatna, M.A. Mendez-Rojas, G. Merino, A. Vella, R. Hoffmann, J. Am. Chem. Soc. 126 (2004) 15309) have suggested PTC chains and lattices of simple C 5 2 - unit in which metal ions are employed to compensate the negative charge. In this account, structures of dimers and trimers beside tetramers containing earth alkali metals have been investigated to check whether they can be employed for this goal. Upon the obtained results one may conclude that thermodynamic instability of these species is a stumbling block.