Synthesis and Characterization by a Single-Crystal XRD Study of [H3O]4[Cu7(NH3)2(H2O)4{B24O39(OH)12}]·13H2O: An Unusual [{(H2O)2(NH3)Cu}2{B2O3(OH)2}2Cu]2+ Trimetallic Bis(dihydroxytrioxidodiborate) Chain Supported by a [{Cu4O}{B20O32(OH)8}]6− Cluster

The unusual [Cu7(NH3)2(H2O)4{B24O39(OH)12}]4− cluster anion, isolated in the form of its hydrated hydronium ion salt, has been crystallized in moderate yield (59%) through a templated self-assembly process from [Cu(NH3)4(H2O)2](OH)2 and B(OH)3 (10 equivalents) in aqueous solution. This novel anionic cluster is comprised of two diborate(2-) ligands bridging a linear {Cu3}6+ framework with this Cu3 fragment interacting with, and further supported by, a known larger [{Cu4O}B20O32(OH)8]6− cluster.