Strontium hydroxide chloride and strontium hydroxide bromide preparation, crystal - Structure, and IR and Raman spectra

The partly hitherto unknown compounds Sr(OH)Cl, Sr(OH)Br mC16 and Sr(OH)Br cP16 have been established by both dehydration of the hydrates (Sr(OH)CI, Sr(OH)Br mC16) and melting together stoichiometric mixtures of Sr(OH)(2) and SrCl2 or SrBr2 (Sr(OH)CI, Sr(OH)Er cP16). The monoclinic polymorph of the bromide is monotropically changed above 650K thigh-temperature X-ray and high-temperature Raman studies) into the cubic modification. Sr(OH)Cl crystallizes in the Cd(OH)Cl structure type (space group P6(3)mc, Z=2, a=414.41(2), c= 995.16(10) pm), Sr(OH)Br mC16 and cP16 crystallizing in own structures (C2/m, Z = 4, a = 1100.66(7), b = 429.55(3), c = 726.25(5) pm, beta= 106.285(4)degrees, P2(1)3, Z = 4, a = 675.79(2) pm). The structures were refined from X-ray powder diffractograms (Sr(OH)Cl: R-I=11.4%, 4668 observations, Sr(OH)Br mon.: R-I = 13%, 1082 observations), neutron powder diffractograms (Sr(OD)Er cub.: R-I=3,8%, 793 observations), and X-ray single-crystal studies, respectively (Sr(OH)Br cub.: R1 =5.02%, 585 independent reflections). The positions of the hydrogen atoms of Sr(OH)Cl and Sr(OH)Br mon, were determined by the method of minimum cohesive energy. Sr(OH)Cl and Sr(OH)Br mon. crystallize in layered structures with monocapped distorted octahedrally (30H(-) and 4X(-)) coordinated strontium ions. Sr(OH)Br cub, crystallizes in a structure built up of three-dimensional nets, the coordination of Sr, however, corresponds to that of Sr(OH)Cl and Sr(OH)Br mon. IR and Raman spectra are presented and discussed together with the structure data with respect to the strength of the O-H ... X hydrogen bonds (stretching modes of matrix isolated OD- ions.