Conformations and crystal packing. The crystal and molecular structure of trans-bis(2,4-pentanedionato)dipyridinenickel(II), Ni(AA)2(py)2

1968 ◽  
Vol 7 (11) ◽  
pp. 2316-2322 ◽  
Author(s):  
Richard C. Elder
1993 ◽  
Vol 58 (9) ◽  
pp. 2121-2127 ◽  
Author(s):  
Josef Přikryl ◽  
Bohumil Kratochvíl ◽  
Jan Ondráček ◽  
Jaroslav Maixner ◽  
Jiří Klicnar ◽  
...  

The title charge-transfer complex crystallizes in the ratio of two molecules of azo dyestuff to one molecule of naphthalene. The crystals are triclinic, space group P1, lattice parameters a = 7.953(1), b = 11.608(2), c = 11.717(2) Å, α = 101.89(2), β = 94.27(2), γ = 109.91(2)°, Z = 2. The structure was solved by direct methods and refined anisotropically to R = 0.054 for 1 768 unique observed reflections. Crystal packing is stabilized by van der Waals forces and partly by π-π stacking interaction among naphthalene, phenyl and pyridine ring of pyridon azo dyestuff.


π -Cyclopentadienyl 1-phenylcyclopentadiene cobalt crystallizes as orthorhombic needles with a = 29.64 ± 0.04 Å, b = 7.70 ± 0.01 Å, c = 10.68 + 0.02 Å; the space group is Pbca . A three-dimensional single-crystal Fourier and least-squares analysis has converged R to 0.089 for the 815 independent reflexions, σ - and π -bonding from the cyclopentadiene ligand to the cobalt ion is evidenced by the conformation of the ligand together with the detailed carbon-carbon bond lengths (average e. s. d. 0.03 Å). The phenyl group occupies the exo -position rather than the endo -site suggested by spectroscopic techniques. The crystal packing is also discussed.


1977 ◽  
Vol 55 (5) ◽  
pp. 849-855 ◽  
Author(s):  
Anthony D. Baranyi ◽  
Mario Onyszchuk ◽  
Yvon Le Page ◽  
Gabrielle Donnay

The title compound has two PbBr2•2[(CH3)2SO] units, Z = 2, in a cell with a = 11.093(2), b = 12.382(3), c = 4.540(1) Å, belonging to space group Pmmn. The structure was solved by Patterson functions and was refined by full-matrix least-squares calculations to a final R of 0.054 for 348 observed diffractometer intensities. Passing through the unit cell are two antiparallel, infinite polar chains, each with symmetry mm2, extending along z and interacting with each other by weak van der Waals forces. Lead(II) is six-coordinate with a close, covalent hemisphere consisting of two bromine atoms [Pb—BrIBrII 2.93(1) Å], and two oxygen atoms [Pb—O,O′ 2.50(3) Å] which subtend an angle of 157.9(9)° at lead, located at the intersection of the O—Pb—O′ and BrI—Pb—BrII perpendicular mirror planes. The other hemisphere consists of bridging bromine atoms from the neighboring PbBr2•2dmso unit [Pb—BrIII,BrIV 3.24(1) Å], resulting in a rectangle of bromine atoms around lead [BrI—Pb—BrII 90.5(1)°, BrIII—Pb—BrIV 80.2(1)°]. The distortion of the octahedral coordination sphere around lead is discussed in terms of (a) a repulsive effect of the Pb(II) valence lone electron-pair, (b) weak Br—S bonding, and (c) crystal packing forces.


1991 ◽  
Vol 44 (12) ◽  
pp. 1761 ◽  
Author(s):  
L Antolini ◽  
A Marchetti ◽  
C Preti ◽  
M Tagliazucchi ◽  
L Tassi ◽  
...  

The synthesis, and crystal and molecular structure of N,N′- diphenylguanidinium m- chlorobenzeneseleninate (C19H18CIN3O2Se), Mr 434.78, are reported. The crystal lattice of the compound belongs to the monoclinic space group P21/c with a 7.277(1), b 12.793(2), c 20.013(4) Ǻ, β 94.733(12)°, V 1859.8 Ǻ3, Z 4, Dobs 1.53 (by flotation), Dcalc 1.555 g cm-3, λ(Mo Kα ) 0.71069 Ǻ, μ 21.0 cm-1, F(000) 880, T 293 K, R 0.057 and Rw 0.059 for 1745 unique observed reflections with I>2.0σ(I). The crystal packing consists of parallel layers of anions intercalated with cations interacting through electrostatic contacts. Vibrational spectra have been also recorded, and are discussed.


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