Guanidinium Ion as a Symmetrical Template in the Formation of Cubic Hydrogen-Bonded Borate Networks with the Boracite Topology

Reaction between boric acid and guanidinium salts in methanolic solution at room temperature in the presence of various bases and anions gives well-formed solvated crystals of composition {[B(OCH₃)₄]₃[C(NH₂)₃]₄}⁺X^-. The products in which X^- = Cl^- and PF₆^- are characterized by single-crystal X-ray diffraction. The tetramethoxyborate and guanidinium components form a highly symmetrical (cubic) hydrogen-bonded 3D network having the “boracite topology” [i.e., the (6³)(6²8⁴) topology]. Highly disordered solvent molecules and anions occupy methyl-surfaced cavities and channels that represent more than 30% of the space.