Three novel selenoborato-closo-dodecaborates:: Syntheses and crystal structures of Rb8[B12(BSe3)6], Rb4Hg2[B12(BSe3)6], and Cs4Hg2CB12(BSe3)6]

The three selenoborates Rh-8[B-12(BSe3)(6)] (P (1) over bar, a 10.512(5) Angstrom, b = 10.450(3) Angstrom, c = 10.946(4) Angstrom, alpha = 104.53(3)degrees, beta = 91.16(3)degrees, gamma = 109.11(3)degrees Z = 1), Cs4Hg2[B-12(BSe3)(6)] (P (1) over bar, a = 9.860(2) Angstrom, b = 10.740(2) Angstrom, c = 11.078(2) Angstrom, alpha = 99.94(3)degrees, beta = 90.81(3)degrees, gamma = 115.97(3)degrees, Z = 1), and Rb4Hg2[B-12(BSe3)(6)] (P (1) over bar, a = 9.593(2)Angstrom, b = 10.458(2)Angstrom, c = 11.131(2)Angstrom, alpha = 99.25(3)degrees, beta = 91.16(3)degrees, gamma = 116.30(3)degrees, Z=1) were prepared from the metal selenides, amorphous boron and selenium by solid state reactions at 700 OC. These new chalcogenoborates contain B-12 icosahedra completely saturated with six trigonal-planar BSe3 entities functioning as bidentate ligands to form a persubstituted closo-dodecaborate anion. The two isotypic compounds Rb4Hg2[B-12(BSe3)(6)] and Cs4Hg2[B-12(BSe3)(6)] are the first selenoborate structures containing a transition metal which are characterized by single crystal diffraction.