Synthesis and crystal structure determination of K3BiO3 and Rb3BiO3

K3BiO3 and Rb3BiO3 have been synthesized for the first time by solid state reactions of the respective binary compounds. K3BiO3 was obtained from Bi2O3 and K2O at 550 degrees C, Rb3BiO3 from Bi2O3 and Rb2O at 650 degrees C. The compounds were structurally examined by single crystal X-ray investigations (K3BiO3: I (4) over bar 3 m, a = 1070.15(2) pm, Z = 8; Rb3BiO3: P2(1) 3, a = 875.48(2) pm, Z = 4). The structures reveal ''isolated'' BiO33- groups. While K3BiO3 is isostructural to Na3BiO3, Rb3BiO3 has the same crystal structure as Cs3BiO3.