Studies on peroxomolybdates XVIII. Crystal structure of ammonium μ-fluoro- μ-oxo-bis[oxodiperoxomolybdate(VI)]- water(2/1), [formula omitted], a dibridged peroxodimolybdate

Abstract

The crystal structure of ammonium μ- fluoro-μ- oxo-bis[oxodiperoxomolybdate(VI)]-water (2 1) , (NH 4) 3[FO{MoO(O 2) 2} 2]· 1 4 H 2O , has been determined from single-crystal X-ray diffraction data. The yellow compound crystallizes as multiple-twins in the monoclinic space group P2 1/ c with a = 13.803(3) A ̊ , b = 11.230(2) A ̊ , c = 15.975(3) A ̊ , β = 109.46(2)° and Z = 8. Full-matrix least-squares refinement of 316 structural parameters gave R = 0.057 for 3265 observed [ I > 3 σ( I)], independent reflections. The [FO{MoO(O 2) 2} 2] 3− anions, of which there are two crystallographically different ones in the asymmetric unit, have approximately C 2v symmetry and are composed of two edge-sharing pentagonal bipyramids, the molybdenum atoms thus being seven-coordinated. The molybdenum atoms are displaced 0.312–0.365 Å from the equatorial planes towards the respective double-bonded apical oxygen atom. Bond distances are as follows: MoO peroxo 1.884(10)–1.975(8) Å, Mo = O apical 1.670(8)–1.682(8) Å, MoF bridge 2.246(6)–2.313(6) Å, MoO bridge 1.925(7)–1.941(7) Å and (OO) peroxo 1.436(15)–1.465(12) Å. Mo ··· Mo is 3.369(1)–3.379(1) Å, MoOMo 120.5(4)–122.6(4)° and MoFMo 94.0(2)–95.5(2)°. The powder photograph of the title compound was recorded at room temperature and was indexed.