“…2.52 Å) and P−O (1.50 Å) distances are very similar in the anhydrous and hydrated complexes. Although the mean P−O distance is essentially identical with that found in 8-coordinated U(H 2 PO 2 ) 4 , the shorter mean U−O distance (2.36 Å) reflects the smaller ionic radius of U 4+ . 1 Thermal ellipsoid (35%) plot showing the atom-numbering scheme and the coordination geometry about the lanthanum atom in (a) La(H 2 PO 2 ) 3 and (b) La(H 2 PO 2 ) 3 ·H 2 O.…”
Section: Resultsmentioning
confidence: 50%
“…The hypophosphite anion plays a rather different role in the structure of Mg(H 2 PO 2 ) 2 ·6H 2 O, each oxygen being hydrogen-bonded to three molecules of water of three different [Mg(H 2 O) 6 ] 2+ octahedra 1l. Zn(H 2 PO 2 ) 2 has a polymeric layer-type structure, whereas Zn(H 2 PO 2 ) 2 ·H 2 O forms a three-dimensional polymeric network, with both Zn−O−Zn and Zn−O−P−O−Zn bridges. , In anhydrous U(H 2 PO 2 ) 4 , hypophosphite anions again serve as bridging groups in linking the uranium centers to yield a three-dimensional network, but the coordination geometry of uranium is approximately square antiprismal …”
The lanthanide hypophosphite complexes Ln(H(2)PO(2))(3) (Ln = La, Pr, Nd) and Ln(H(2)PO(2))(3).H(2)O (Ln = La, Pr) crystallize in the space group P&onemacr; (No. 2), Z = 2. The lattice constants for La(H(2)PO(2))(3) are a = 6.7912(6) Å, b = 7.0801(8) Å, c = 8.863(1) Å, alpha = 82.64(1) degrees, beta = 74.43(1)( o), gamma = 71.91(1) degrees; for La(H(2)PO(2))(3).H(2)O, a = 7.2291(4) Å, b = 7.983(1) Å, c = 8.934(1) Å, alpha =110.57(1) degrees, beta = 98.26(1) degrees, gamma = 104.35(1) degrees. In both structures hypophosphite ions bridge adjacent 8-coordinate lanthanide ions to give infinite chains. Infrared and Raman spectra (300-20 K) are shown to be consistent with the crystallographic data, with 52 of the 54 fundamental hypophosphite modes of vibration assigned. The electronic spectra of the anhydrous compounds consist mainly of bands due to pure electronic electric dipole transitions. Two-center vibronic transitions observed in the (3)H(4) --> (1)D(2) spectrum of Pr(H(2)PO(2))(3) are not well-simulated by a model with dipole-dipole interaction terms between the two centers. The energy level scheme of Pr(3+) in Pr(H(2)PO(2))(3) was fitted to a model Hamiltonian for a C(2)(v)() site symmetry Pr(3+) ion, including configuration interaction of 4f(2) with 4f6p. Theoretical crystal field parameters were in reasonable agreement with those derived from the energy level fitting. The results highlight the C(2)(v)() (k even) and C(1) (k odd) distortions from the ideal D(4)(d)() antiprismal structure, which slightly modify the 4f(2) energy level scheme, and largely determine the spectral intensities in Pr(H(2)PO(2))(3), respectively. The derived energy level scheme of Nd(H(2)PO(2))(3) is similar to that for 8-coordinated Nd(3+) in NdCl(3).6H(2)O.
“…2.52 Å) and P−O (1.50 Å) distances are very similar in the anhydrous and hydrated complexes. Although the mean P−O distance is essentially identical with that found in 8-coordinated U(H 2 PO 2 ) 4 , the shorter mean U−O distance (2.36 Å) reflects the smaller ionic radius of U 4+ . 1 Thermal ellipsoid (35%) plot showing the atom-numbering scheme and the coordination geometry about the lanthanum atom in (a) La(H 2 PO 2 ) 3 and (b) La(H 2 PO 2 ) 3 ·H 2 O.…”
Section: Resultsmentioning
confidence: 50%
“…The hypophosphite anion plays a rather different role in the structure of Mg(H 2 PO 2 ) 2 ·6H 2 O, each oxygen being hydrogen-bonded to three molecules of water of three different [Mg(H 2 O) 6 ] 2+ octahedra 1l. Zn(H 2 PO 2 ) 2 has a polymeric layer-type structure, whereas Zn(H 2 PO 2 ) 2 ·H 2 O forms a three-dimensional polymeric network, with both Zn−O−Zn and Zn−O−P−O−Zn bridges. , In anhydrous U(H 2 PO 2 ) 4 , hypophosphite anions again serve as bridging groups in linking the uranium centers to yield a three-dimensional network, but the coordination geometry of uranium is approximately square antiprismal …”
The lanthanide hypophosphite complexes Ln(H(2)PO(2))(3) (Ln = La, Pr, Nd) and Ln(H(2)PO(2))(3).H(2)O (Ln = La, Pr) crystallize in the space group P&onemacr; (No. 2), Z = 2. The lattice constants for La(H(2)PO(2))(3) are a = 6.7912(6) Å, b = 7.0801(8) Å, c = 8.863(1) Å, alpha = 82.64(1) degrees, beta = 74.43(1)( o), gamma = 71.91(1) degrees; for La(H(2)PO(2))(3).H(2)O, a = 7.2291(4) Å, b = 7.983(1) Å, c = 8.934(1) Å, alpha =110.57(1) degrees, beta = 98.26(1) degrees, gamma = 104.35(1) degrees. In both structures hypophosphite ions bridge adjacent 8-coordinate lanthanide ions to give infinite chains. Infrared and Raman spectra (300-20 K) are shown to be consistent with the crystallographic data, with 52 of the 54 fundamental hypophosphite modes of vibration assigned. The electronic spectra of the anhydrous compounds consist mainly of bands due to pure electronic electric dipole transitions. Two-center vibronic transitions observed in the (3)H(4) --> (1)D(2) spectrum of Pr(H(2)PO(2))(3) are not well-simulated by a model with dipole-dipole interaction terms between the two centers. The energy level scheme of Pr(3+) in Pr(H(2)PO(2))(3) was fitted to a model Hamiltonian for a C(2)(v)() site symmetry Pr(3+) ion, including configuration interaction of 4f(2) with 4f6p. Theoretical crystal field parameters were in reasonable agreement with those derived from the energy level fitting. The results highlight the C(2)(v)() (k even) and C(1) (k odd) distortions from the ideal D(4)(d)() antiprismal structure, which slightly modify the 4f(2) energy level scheme, and largely determine the spectral intensities in Pr(H(2)PO(2))(3), respectively. The derived energy level scheme of Nd(H(2)PO(2))(3) is similar to that for 8-coordinated Nd(3+) in NdCl(3).6H(2)O.
“…The ®rst structural studies of ammonium hypophosphite and hexahydrates of cobalt, nickel and magnesium hypophosphites were reported 65 years ago (Zachariasen & Mooney, 1934;Ferrari & Colla, 1937). The crystal structures of hypophosphites of anhydrous calcium (Wyckoff, 1964), zinc (Tanner et al, 1997), germanium (Weakley, 1983), erbium (Aslanov et al, 1975), uranium (Tanner et al, 1992), and a urea complex of copper ) are known. No structural data for pure copper(II) hypophosphite, (I), have yet been reported.…”
Copper(II) hypophosphite has been shown to exist as several polymorphs. The crystal structures of monoclinic alpha-, orthorhombic beta- and orthorhombic gamma-Cu(H(2)PO(2))(2) have been determined at different temperatures. The geometry of the hypophosphite anion in all three polymorphs is very close to the idealized one, with point symmetry mm2. Despite having different space groups, the structures of the alpha- and beta-polymorphs are very similar. The polymeric layers formed by the Cu atoms and the hypophosphite ions, which are identical in the alpha- and beta-polymorphs, stack in the third dimension in different ways. Each hypophosphite anion is coordinated to three Cu atoms. On cooling, a minimum amount of contraction was observed in the direction normal to the layers. The structure of the polymeric layers in the gamma-polymorph is quite different. There are two symmetry-independent hypophosphite anions; the first is coordinated to two Cu atoms, while the second is coordinated to four Cu atoms. In all three polymorphs, the Cu atoms are coordinated by six O atoms of six hypophosphite anions, forming tetragonal bipyramids; in the alpha- and beta-polymorphs, there are four short and two long Cu-O distances, while in the gamma-polymorph, there are four long and two short Cu-O distances.
“…In 1992 we synthesized and characterized the new uranium(IV) compound U(H 2 PO 2 ) 4 . The edges of the dark green plates obtained were found to corrode to a paler yellow color after a period of storage in moist air for several years, indicating oxidation to uranium(VI) as the uranyl ion.…”
The new compounds UO(2)(H(2)PO(2))(2).H(2)O (1) and UO(2)(H(2)PO(2))(2).H(3)PO(2) (2) crystallize in the space groups P2(1)/n and P2(1)2(1)2(1), respectively, each with Z = 4. For 1, a = 7.686(2) Å, b = 9.275(2) Å, c = 11.027(2) Å, alpha = 90 degrees, beta = 92.32(3) degrees, gamma = 90 degrees; for 2, a = 7.1572(4) Å, b = 7.2363(6) Å, c = 17.554(2) Å, alpha = beta = gamma = 90 degrees. Each uranium atom, situated at a general position, has a distorted pentagonal bipyramidal coordination geometry, and U-O-P-O-U bridges form differently oriented chains in 1 and a three-dimensional network structure in 2. H(3)PO(2) serves as a terminal monodentate ligand in 2. The infrared and Raman spectra of 1 and 2 show (i) characteristic uranyl modes of vibration; (ii) partially resolved unit cell group modes of hypophosphite anions; and (iii) bands due to water and H(3)PO(2), respectively. The C(1) site symmetry in these compounds makes their spectral properties useful in evaluating the presence of additional electronic transitions not identified in the analyses of higher symmetry uranyl compounds. In the region between 20 000 and 29 000 cm(-)(1), 12 electronic transitions have been located and assigned. The luminescence from both compounds is weak due to competing nonradiative processes, and the major differences from that of UO(2)(2+) at centrosymmetric sites arise from the electric dipole intensity enhancement of the zero-phonon line and the appearance of progressions in the uranyl antisymmetric stretching mode. Water and hypophosphite modes are identified in the luminescence of 1 and 2, respectively. The anharmonicities of uranyl stretching modes in 1 are compared with those in other uranyl systems. The Franck-Condon analysis of the absorption and emission spectra of 1 show a U-O bond length increase of 5 +/- 1 pm on excitation from to sigma(u)delta(u), compared with values ranging from 4 to 9 pm for other uranyl systems.
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