title: Structures of the monohydrate and dihydrate of (bidentate pyrophosphato) trans-diammine cis-diaqua chromium (III).
abstract: (OC-6-32)-Diamminediaqua [pyrophosphato(3-)]chromium(III) monohydrate, [Cr(NH3)2-(H2O)2(HP2O7)]. H2O, Mr = 315.1, triclinic, P1, a = 7.127 (2), b = 8.390 (2), c = 9.619 (2) A, alpha = 72.14 (2), beta = 98.86 (2), gamma = 76.98 (3) degrees, V = 517.7 (3) A3, Z = 2, Dx = 2.02 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 129 cm-1, F(000) = 322, T = 293 K. (OC-6-32)-Diamminediaqua[pyrophosphato(3-)]-chromium(III) dihydrate, 0.5( [Cr(NH3)2(H2O)2-(HP2O7)].2H2O), Mr = 0.5(333.1), monoclinic, C2/m, a = 13.118 (3), b = 12.101 (3), c = 7.436 (2) A, beta = 105.09 (2) degrees, V = 1139.7 (3) A3, Z = 8, Dx = 1.94 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 118 cm-1, F(000) = 684, T = 293 K. The structures were solved by the multi-solution technique and refined by the method of least squares to yield a final R index of 0.057 for 986 reflections in the monohydrate and a final R index of 0.043 for 1030 reflections in the dihydrate. The six-membered chromium pyrophosphate chelate ring is in a boat conformation for the monohydrate with an intramolecular hydrogen bond between an ammonia proton and a pyrophosphate O atom. In the dihydrate, the chelate ring is bisected by the mirror plane resulting in an unusual planar chelate ring conformation which does not permit intramolecular hydrogen bonding.
authors.affiliation: Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
authors.forename: T P
authors.initials: TP
authors.lastname: Haromy
authors.forename: J
authors.initials: J
authors.lastname: Rawlings
authors.forename: W W
authors.initials: WW
authors.lastname: Cleland
authors.forename: M
authors.initials: M
authors.lastname: Sundaralingam
mesh_terms: D002857:Chromium / Q000737:chemistry* / Q000302:isolation & purification; D011756:Diphosphates / Q000737:chemistry* / Q000302:isolation & purification; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D011756:Diphosphates; D002857:Chromium; C068434:diamminediaqua(pyrophosphato(3-))chromium (III)