Synthesis and crystal structure of manganese(II) and zinc amides, Mn(NH2)(2) and Zn(NH2)(2)

Metal powders of manganese resp. zinc react with supercritical ammonia in a utoclaves in the presence of a mineralizer Na2Mn(NH2)(4) resp. Na2Zn(NH2)(4 ). 0.5NH(3) to well crystallized ruby-red Mn(NH2)(2) (p(NH3) = 100 bar, T = 130 degrees C, 10 d) resp. colourless Zn(NH2)(2) (p(NH3) = 3.8 kbar, T = 2 50 degrees C, 60 d). The structures including all H-positions were solved b y x-ray single crystal data: Mn(NH2)(2): I4(1)/acd, Z = 32, a = 10.185(6) Angstrom, c = 20.349(7) Angstr om, N(F-o) with F-o(2) > 3 sigma (F-o(2)) = 313, N(parameter) = 45, R/R-w = 0.038/0.043. Zn(NH2)(2):I4(1)/acd, Z = 32, a = 9.973(3) Angstrom, c = 19.644(5) Angstrom , N(F-o) with F-o(2) > 3 sigma (F-o(2)) = 489, N(parameter) = 45, R/R-w = 0 .038/0.043. Both compounds crystallize isotypic with Mg(NH2)(2) [1] resp. Be(NH2)(2) [2 ]. Nitrogen of the amide ions is distorted cubic close packed. One quarter of tetrahedral voids is occupied by Mn2+-resp. Zn2+-ions in such an ordered way that units M-4(NK2)(6)(NH2)(4/2) occur. The H-atoms of the anions have such an orientation that the distance to neighboured cations is optimum.