Versatile Coordination Mode of LiNaB<sub>8</sub>O<sub>13</sub> and α- and β‑LiKB<sub>8</sub>O<sub>13</sub> via the Flexible Assembly of Four-Connected B<sub>5</sub>O<sub>10</sub> and B<sub>3</sub>O<sub>7</sub> Groups

Three new alkali-metal mixed borates, LiNaB<sub>8</sub>O<sub>13</sub>, α-LiKB<sub>8</sub>O<sub>13</sub>, and β-LiKB<sub>8</sub>O<sub>13</sub>, containing a <sup>3</sup><sub>∞</sub>[B<sub>8</sub>O<sub>13</sub>] three-dimensional network have been successfully synthesized. Their fundamental building block is [B<sub>8</sub>O<sub>16</sub>]<sup>8–</sup> formed by the vertex-sharing [B<sub>5</sub>O<sub>10</sub>]<sup>5–</sup> and [B<sub>3</sub>O<sub>7</sub>]<sup>5–</sup> groups, which are topologically identical when they are considered as four-connected nodes. The viewpoints give us a feasible way to investigate the versatile structure assembly of borates with a complex network.