Further Examples of the P-O-P Connection in Borophosphates: Synthesis and Characterization of Li2Cs2B2P4O15, LiK2BP2O8, and Li3M2BP4O14 (M=K, Rb)

A new series of anhydrous mixed alkali-metal borophosphatesLi2Cs2B2P4O15 (1), LiK2BP2O8 (2), Li3K2BP4O14 (3), and Li3Rb2BP4O14 (4)have been successfully synthesized by using the conventional solid-state reaction method. Compound 1 contains a novel fundamental building unit (FBU), [B4P8O30], with B/P=1:2. Compound 2 contains an FBU of [B2P4O16] with B/P=1:2. Compounds 3 and 4 are isotypic, and they have a [B(P2O7)2] unit as their FBU. In all four compounds, their FBUs are connected through corner sharing to generate layered anionic partial structures, and then further linked with metallic polyhedra to form three-dimensional (3D) frameworks. Most interestingly, three of the four compounds contain direct P-O-P connections in their structures, which is extremely rare among borophosphates. Thermal analyses, IR spectroscopy, and UV/Vis/near-IR diffuse reflectance spectroscopy have also been performed on the four title compounds.