Multicomponent Assembly of Anionic and Neutral Decanuclear Copper(II) Phosphonate Cages.

A multicomponent synthetic strategy involving copper(II) ions, tert-butylphosphonic acid (t-BuPO3H2) and 3-substituted pyrazole ligands has been adopted for the synthesis of soluble molecular copper(II) phosphonates. The use of six different 3-substituted pyrazoles, 3-R-PzH [R = H, Me, CF3, Ph, 2-pyridyl (2-Py), and 2-methoxyphenyl (2-MeO-C6H4)] as ancillary ligands afforded nine different decanuclear cages, [Cu5(μ3-OH)2(O3P-t-Bu)3(3-R-Pz)2(X)2]2·(Y) where R = H, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (1); R = Me, X = 3-MePzH, and Y = solvent (2); R = Me, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (3); R = CF3, X = t-BuPO3H, and Y = (Et3NH+)4(solvent) (4); R = Ph, X = 3-PhPzH, and Y = solvent (5); R = 2-Py, X = 0.5 MeOH, and Y = solvent (6); R = 2-Py, X = none, and Y = solvent (7); R = 2-Py, X = H2O, and Y = (Et3NH+·PF6-)2(solvent) (8); R = 2-MeO-C6H4, X = MeOH or 0.5:0.5 MeOH/H2O, and Y = solvent (9). Compounds 1-6, 8, and 9 were isolated using a direct synthetic method which involves the reaction of copper(II) salts and the ligands, while 7 was obtained from an indirect route involving the reaction of preformed copper-pyridylpyrazolate precursor complexes and t-BuPO3H2. The decametallic compounds 1-9 possess a butterfly shaped core. The core of the cages 1, 3, and 4 are tetraanionic and contain more phosphonates than pyrazole ligands, while the other cages are neutral and contain more pyrazoles than phosphonate ligands. Compounds 1-6 have been studied by electrospray ionization-high-resolution mass spectrometry (ESI-HRMS). The decanuclear cage 6 was shown to be a good plasmid modifier. [ABSTRACT FROM AUTHOR]