Crystal structures of M2[B10H10] (M = Na, K, Rb) via real-space simulated annealing powder techniques

Abstract Alkali metal decahydro- closo -decaborates M 2 [B 10 H 10 ] (M = Na, Rb, Cs) were synthesised by ion-exchange and characterised via infrared and 11 B-NMR spectroscopy. The crystal structures of Na 2 [B 10 H 10 ], K 2 [B 10 H 10 ], and Rb 2 [B 10 H 10 ] were determined from X-ray powder diffraction data using real-space techniques. The compounds crystallise in the monoclinic space group P 2 1 / n (no. 14) with the lattice constants: Na 2 [B 10 H 10 ]: a = 1028.28(6) pm, b = 1302.18(5) pm, c = 667.34(3) pm, β = 93.754(3)°; K 2 [B 10 H 10 ]: a = 1285.54(8) pm, b = 1117.84(7) pm, c = 682.27(4) pm, β = 93.357(3)°; Rb 2 [B 10 H 10 ]: a = 1320.04(7) pm, b = 1136.88(6) pm, c = 704.23(4) pm, β = 94.158(3)°. The hydroborate anions are arranged almost hexa gonally with alkali metal cat ions in the tetrahedral interstices.