Synthesis and crystal structure of potassium bis(malonato)borate

Potassium bis(malonato) borate C6H4BKO8 ( I) was synthesized for the first time in an aqueous medium. Well-shaped single crystals were formed. Their X-ray diffraction structure ( space group P (1) over bar, a = 7.4073( 2) angstrom, b = 7.9161( 2) angstrom, c = 9.0755( 2) angstrom, alpha 113.225(1)degrees, beta = 91.553( 1)degrees, gamma = 104.760(2)degrees, Z = 2) was refined by the full-matrix least-squares method in the anisotropic ( K, C, O, B) or isotropic ( H) approximations to R1 = 0.394, wR2 = 0.1080, 2661 independent reflections (Bruker - Nonius KappaCCD, lambda MoK alpha radiation). The structure is formed by spirane-type complex anions and potassium cations. A complex anion consists of two malonic acid molecules coordinated in the bidentate mode to the same four-coordinate boron atom. The K+ coordination geometry is an irregular nine-vertex polyhedron formed by the oxygen atoms of seven complex anions. The structure of compound I is layered.