Jana Podlahová

Trigonal bipyramidal penta-aquazinc(II): crystal structure of penta-aquazinc(II) bis(3,3′,3″-phosphinetriyltripropionato)dizincate(II,II) heptahydrate

Crystals of the title compound are hexagonal, space group P61 or P65. The crystal structure was determined by the heavy-atom method from 2 675 unique reflections and refined to R= 0.059. The structure can be best formulated as an ionic polymer with the composition ([Zn(H2O)5][Zn2{P(CH2CH2CO2)3}2]·7H2O)n. It consists of a three-dimensional network of [Zn{P(CH2CH2CO2)3}]– anions, where the zinc atoms are each tetrahedrally co-ordinated by three carboxyl oxygen atoms belonging to three different 3,3′,3″-phosphinetriyltripropionato ligands [Zn–O, 1.950(12)–1.991 (13)A] and by one phosphorus atom from a fourth ligand [Zn–P, 2.405(4) and 2.429(4)A; the first crystallographically documented zinc–phosphine bond]. Zinc cations are located in holes of the network as the hitherto unknown [Zn(H2O)5]2+ moieties with trigonal bipyramidal arrangement. The structure is stabilized by hydrogen bonding in which carboxylate oxygen atoms and both coordinated and lattice water molecules are involved.

Oxidative addition of diphenylphosphinoacetic acid to rhodium: crystal structures of the intermediate, [RhCl(H)(Ph2PCH2CO2-OP)(Ph2PCH2CO2H-P)2] and of the final product, [Rh(Ph2PCH2CO2-OP)3]

The difference in reactivity towards RhI between simple tertiary phosphines and diphenylphosphino-acetic acid can be explained by the assumption that the latter ligand, besides monodentate P bonding, tends also to react by oxidative addition of its carboxyl group, yielding P,O-chelated rhodium(III) complexes. Crystal structures of the final product, fac-[Rh(Ph2PCH2CO2)3]·PhNO2·H2O, and of the key intermediate, mer-[RhCl(H)(Ph2PCH2CO2)(Ph2PCH2CO2H)2]·C4H8O, were determined. The latter structure is unique in that it contains both hydride and a carboxylic proton in one molecule.

Crystal structure of a compound composed of a cluster cation and a cluster anion

Abstract X-Ray crystal structure determination of the crystalline material resulting from Rh-catalysed carbonylation of N,N -allylethylamine in the presence of trimethylphosphine revealed the composition FeRh 8 (PMe)(PMe 3 ) 5 (CO) 20 for the product, with the iron originating presumably from an impurity in the CO used. The compound is complsed of the triangular cluster cation, [Rh 3 (μ 3 -PMe)(PMe 3 ) 4 -(CO 5 ] + , and of the octahedral, heterometallic cluster anion, [FeRh 5 (PMe 3 )(CO) 15 ] − , packed at Van der Waals distances in a distorted CsCl arrangement. Both clusters belong to well-documented types; features characteristics for this particular structure can be ascribed to the high basicity and low steric bulk of the phosphine.

Molecular spectra and X-ray study of the alkali hydrogen selenites MHSeO3

Abstract A study of the molecular spectra confirmed that the protons are localized close to one of the oxygen atoms in the hydrogen bonds in the compounds LiHSeO3, KHSeO3, RbHSeO3, and CsHSeO3. The character of the NaHSeO3 spectrum indicates that part of the protons are in ordered positions, which is in agreement with the results of the structural analysis published earlier. Down to a temperature of 77 K, no phase transition connected with a change in the proton ordering was found during the study of the molecular spectra of the test compounds. X-ray diffraction confirmed structural isomorphy of RbHSeO3 with KHSeO3, with the P 1 space group, a = 5.192(2)A, b = 5.876(3)A, c = 6.578(3)A, α = 110.8(1)°, β = 94.5(1)°, γ = 88.8(1)°, Z = 2. CsHSeO3 belongs to the orthorhombic system, with the Pna21 space group, a = 6.431(3)A, b = 14.031(7)A, c = 4.820(2)A, V = 434.9A3, Z = 4. The structure of this compound was determined using X-ray diffraction for 1053 independent reflections with R = 0.071. The independent part of the unit cell contains the Cs+ cation, to which 10 oxygen atoms are coordinated from 6 different HSeO−3 anions and the pyramidal HSeO−3 anion. The hydrogen selenite anions are hydrogen bonded to form spiral chains along the c-axis. The SeO(H) distance corresponds to an asymmetrical arrangement of the hydrogen bond. The space group found and the asymmetrical position of the proton in the hydrogen bond are in agreement with the pyroelectric behavior of the compound and do not exclude ferroelectric properties of this compound even at laboratory temperature.

Structure elucidation of roemeridine by X-ray crystallography

Abstract The structure of roemeridine, the major alkaloid from Roemeria hybrida was established by X-ray crystallography. Structure-significant features of the 1H and 13C NMR spectral mass spectral fragmentations are reported.

Nickel(II) complexes of ethylenediphosphinetetra-acetic acid☆

Abstract Ethylenediphosphinetetraacetic acid (H 4 L) coordinates nickel(II) preferentially as a chelating di(tertiary phosphine). The two complexes identified in non-aqueous solutions are cis -square planar NiBr 2 (H 4 L) and square-pyramidal [NiBr 2 (H 4 L) 2 Br; both structures are retained in the solid state. The square planar anion NiL 2 6− is the predominant complex in a neutral aqueous solution. A number of its solid salts M 6 NiL 2 ·aq (M = Na, 1 2 divalent metal) has the same square planar NiP 4 core. The compound Ni 2 L·8H 2 O also belongs to this series and should be formulated as Ni 3 [NiL 2 ]·16H 2 O: one nickel(II) is located in the NiP 4 core and the remaining three are coordinated by the carboxyl group oxygen atoms and water molecules in a roughly octahedral environment. The results are based on preparative, X-ray powder, magnetic susceptibility, conductometric, UV-VIS, NMR, IR (both normal and 62 Ni) and XPS spectral studies.

X-ray crystal structure of manganese(II) bis(ethylenediphosphinetetraacetato)nickelate(II) hexadecahydrate

X-ray structure analysis of the title compound (diffractometer data, R = 0.061 for 2805 reflections) confirmed the structure proposed on the basis of spectral evidence for the series of isostructural complexes, M3[NiL2 (H2O)16, where H4L = (HO2CCH2)2PCH2CH2P(CH2CO2H)2 and M = Mn, Fe, Co, Ni, Zn or Cd. The compound studied is monoclinic, P21/c, a = 9.990(3), b = 28.51(2), c = 14.828(9) A, β =94.50(5)°, Z = 4. Nickel(II) is coordinated by two P,P-chelating ligand anions in a rather distorted square planar environment. The carboxyl groups of the ligand are not coordinated to nickel; three of them remain free and five are bonded, together with 10 of the total of 16 water molecules, to the manganese(II) ions. The environments of three manganese ions thus formed are all nearly octahedral but differ in the number and bonding mode of the carboxyls (monodentate and/or bridging bidentate). The carboxyl-to-manganese bonds produce a three-dimensional structure of the compound which is further stabilized by hydrogen bonding.

Nickel(II) complexes of methylphosphinediacetic acid

Abstract Methylphosphinediacetic acid (H2G) is coordinated to nickel(II) in two different ways, depending on whether its carboxyl groups are protonated or dissociated. The acid behaves as a monodentate tertiary phosphine in that it yields a series of trans-square planar NiX2(H2G)2 complexes (X = Cl, Br, NCS or CN) which are stable in the solid state and as solutions in polar non-aqueous solvents. In neutral aqueous solution the NiG22− complex is the predominant species (logβ2 = 8.24 at 25°C and I = 0.1) even in excess nickel(II). Solid NiG·4H2O is the nickel salt of this anion, Ni[NiG2]·8H2O. The X-ray structural determination of the barium salt, BaNiG2·NaClO4·5H2O, revealed the uncommon cis-square planar arrangement around nickel with the G2− anions acting as chelating P,O-bidentate to nickel and as O-monodentate to barium. Sodium and perchlorate ions are located between the complex units and, surprisingly, cannot be removed on recrystallization.