Novel barium beryllates Ba[Be2N2] and Ba-3[Be5O8]: syntheses, crystal structures and bonding properties

Abstract

Ba[Be2N2] was prepared as a yellow-green microcrystalline powder by reaction of Ba2N with Be3N2 under nitrogen atmosphere. The crystal structure Rietfeld refinements (space group I4/mcm, a = 566.46(5) pm, c = 839.42(9) pm, R-int = 4.73 %, R-prof = 9.16 %) reveal the compound to crystallize as an isotype of the nitridoberyllates A[Be2N2] (A = Ca, Sr) consisting of planar 4.8(2) nets (2)(infinity)[(Be2N2)(2-)] of mutually trigonal planar coordinated Be and N species. Averaged magnetic susceptibility values for the anion [(Be2N2)(2-)] determined from measurements on A[Be2N2] with A = Mg, Ca, Ba allow to derive a diamagnetic increment for N3- chi(dia) = (-13 +/- 1stat.) (.) 10(-6)emu mol(-1). Colorless Ba-3[Be5O8] was first obtained as an oxidation product of Ba[Be2N2] in air. The crystal structure was solved and refined from single crystal X-ray diffaction data (space group Pnma, a = 942.9(1) pm, b = 1163.47(7) pm, c = 742.1(1) pm, R1 = 2.99 %, wR2 = 7.15 %) and contains infinite rods of Be in trigonal planar, tetrahedral and 3 + 1 coordination by O. The crystal structure is discussed in context with other known oxoberyllates. Electronic structure calculations and electron localization function diagrams for both compounds support the classification as nitrido- and oxoberyllate, respectively.