Ni-N Distances Research Articles

Structures of Nickel(II) and Copper(II) Complexes of 14-Membered Macrocyclic Quadridentate Ligands

The structures of 41 Ni(II) and 17 Cu(II) complexes of macrocyclic quadridentate ligands have been analyzed, and are discussed about bond lengths, bond angles, conformations, and configurations, upon which many conclusions are formed. The inter- or intra-molecular hydrogen bonds exist among ligands and hydrates in many compounds and play an important role in the structures. There are exhibited two distinct peaks on the histogram of the average Ni-N distances, corresponding to four coordination and six coordination; these average Ni-N distances are 1.95(4) Å and 2.10(5) Å, respectively. The most probable structures of Ni(II) macrocyclic compounds have coordination number six for the metal ion, chair forms for six-membered rings, planar structure for the metal ion and the four donor atoms of the quadridentate ligand and an inversion center at the central metal ion.

Coordination of Hydrazone Derivatives of 2,2'-Bipyridine-6-carbaldehyde. Electronic and Structural Aspects of the Iron(II), Cobalt(II) and Nickel(II) Complexes

Iron(II), cobalt(II) and nickel(II) [MN6]2+ type complexes of the tridentate terimine ligands 2,2′-bipyridine-6-carbaldehyde phenylhydrazone ( bph ) and 2,2′-bipyridine-6-carbaldehyde 2-pyridylhydrazone ( bpyh ) have been prepared. The electronic spectrum of the [NiN6]2+ species indicates that the field strength of these ligands is near that at the iron(II) singlet/quintet crossover. Magnetic and Mossbauer spectral data reveal that salts of [Fe( bph )2]2+ are essentially low spin, while those of [Fe( bpyh )2]2+ are high spin. Salts of [Co( bph )2]2+ have strongly temperature-dependent magnetic moments which indicate a thermally induced doublet ↔ quartet spin transition in the metal atom. The structure of [Ni( bph )2][ClO4]2 reveals meridional coordination of the tridentate units, the azomethine nitrogen of the hydrazone moiety being bound to the metal atom. There is significant twisting (8.3°) of the two pyridyl rings in each ligand molecule about the interring bridge. The [NiN6]2+ fragment is tetragonally compressed and the mean Ni-N distance is 2.09 Ǻ. [Ni( bph )2][ClO4]2 is monoclinic, space group C2/c, Z = 4, a 23.949(3), b 7.868(1), c 21.303(3)Ǻ, β 117.95(2)°.

Synthesis, structure, and properties of a trinuclear and a mononuclear nickel(II) complex of N,N'-dimethyl-N,N'-bis(.beta.-mercaptoethyl)ethylenediamine

The N 2 S 2 ligand N,N'-dimethyl-N,N'-bis(β-mercaptoethyl)ethylenediamine, H 2 L, reacts with NiCl 2 •6H 2 O in methanol solution to yield a trinuclear species of stoichiometry [Ni 3 L 2 ]Cl 2 •2H 2 O. This compound crystallizes in the monoclinic space group P2 1 /n with a=19.917 (7) A, b=5.453 (3) A, c=13.508 (6) A, β=100.81 (4)°, and Z=2. The trinuclear unit consists of two pseudosquare-planar terminal NiN 2 S 2 environments arranged in a chair conformation about a central NiS 4 plane, with the central nickel occupying a crystallographic inversion center. A dihedral angle of 107.84 (7)° exists between nickel planes unrelated by symmetry. Ni-N distances are 1.938 (4) and 1.951 (3) A, Ni-S distances in the NiN 2 S 2 environment are 2.144 (1) and 2.160 (1) A, and Ni-S distances of the NiS 4 center are 2.219 (1) and 2.216 (1) A. The same lignad, under aprotic conditions, reacts with bis(acetylacetonato)nickel(II) to give a neutral mononuclear [NiL] unit with an NiN 2 S 2 chromophore. The trinuclear and mononuclear species are compared with respect to their syntheses and NMR and electronic absorption spectra

Structure of [N,N'-propylenebis(2-pyrrolylmethyleneaminato)]nickel(II).

[Ni(C13H14N4)], Mr = 284.98, monoclinic, P2(1)/c, a = 10.096 (2), b = 9.360 (2), c = 30.565 (4) A, beta = 119.45 (2) degrees, V = 2515.1 (9) A3, Z = 8, Dx = 1.505 g cm-3, Cu K alpha, lambda = 1.5418 A, mu = 20.22 cm-1, F(000) = 1168, T = 298 (2) K, 437 parameters refined, final R = 0.038 for all 2587 reflections. The complex takes a square-planar geometry around the Ni atom. Although the coordination geometries of the two crystallographically independent complexes are quite similar to each other, significant differences in planarity and Ni-N distances are observed.

Structural Study of Bromo-Bridged One-Dimensional NiII–NiIVMixed Valence Complexes by Means of Exafs

Nickel K-edge and Bromine K-edge EXAFS spectra have been measured for Br-bridged one-dimensional NiII-NiIV mixed valence compounds and their reference NiII and NiIV complexes. Fourier transforms of the Br K- and Ni K-edge EXAFS data of the mixed valence compounds show one and two sharp peaks, respectively, assigned to the Br-Ni distance, and the Ni-N and Ni-Br distances. By applying least-squares curve-fitting analyses for the Fourier back-transformed first peaks, a mean NiIV-Br distance for the mixed valence compounds has been determined to be 2.64 A, which is comparable to 2.63 A for the discrete NiIII complex. This suggests a significant elongation of the NiIV-Br bond owing to the charge transfer interaction between the NiII and NiIV atoms, resulting in the high electrical conductivities of NiII–NiIV compounds as compared with those of the Pd and Pt analogues. Mean Ni-N distances were accurately determined and were found to increase in the order, octahedral high-spin NiII > octahedral NiIII ≃ octahedra...

Structures of tetrakis(1,2-dimethylimidazole)MII diperchlorates (MII = Ni,Cu).

[Ni(C5H8N2)4]2+.2ClO4-, Mr = 642.14, monoclinic, P2(1)/n, a = 17.938 (2), b = 14.438 (2), c = 11.336 (2) A, beta = 93.38 (1) degrees, V = 2931 (1) A3, Z = 4, Dm = 1.44 (1), D chi = 1.455 Mg m-3, mu(Mo K alpha, lambda = 0.71073 A) = 0.90 mm-1, F(000) = 1336, T = 297 (1) K, RF = 0.061, wRF = 0.076 for 2676 reflections. [Cu(C5H8N2)4]2+.2ClO4-, Mr = 646.97, monoclinic, P2(1)/n, a = 98.413 (7) degrees, V = 2873 (1) A3, Z = 4, Dm = 1.47 (1), D chi = 1.496 Mg m-3, mu(Mo K alpha, lambda = 0.71073 A) = 1.00 mm-1, F(000) = 1340, T = 297 (1) K, RF = 0.053, wRF = 0.069 for 2889 reflections. Three of the four ClO4 groups in both structures showed disorder; they were modeled as single-site Cl atoms with unrestrained low-occupancy O atoms. Each NiII ion is coordinated in a distorted square-planar fashion by four N donor atoms from the dimethylimidazole groups. The Ni-N distances are typical. In the Cu complex, one ligand showed an approximate twofold disorder about the Cu-N(im) direction. Each CuII ion also has four square-planar equatorial Cu-N(im) bonds and, in addition, shows unusually weak axial coordination by two O(ClO4) atoms. The Cu-O(ClO4) distances are substantially longer than those found for typical tetragonal CuN4O2(ClO4) coordination, and the observed Cu-O-Cl angles are much larger than usual.

Structural heterogeneity and purification of protein-free F430 from the cytoplasm of Methanobacterium thermoautotrophicum.

F430 is the nickel containing tetrapyrrole cofactor of S-methyl coenzyme M methylreductase, the enzyme that catalyzes the final step of methane production by methanogenic bacteria: the reduction of S-methyl coenzyme M (H3CSCH2CH2SO3-) to methane and coenzyme M (HSCH2CH2SO3-). The protein-free F430 obtained from the cytosol of Methanobacterium thermoautotrophicum, strain delta H, exists predominantly in two isomeric forms that differ in relative stereochemical disposition of acid side chains at the 12 and 13 positions of the macrocycle periphery (Pfaltz, A., Livingston, D. A., Jaun, B., Diekert, G., Thauer, R. K., and Eschenmoser, A. (1985) Helv. Chim. Acta 68, 1338-1358). A simple one-step chromatographic procedure for the large-scale separation of these isomers is described. X-ray absorption spectroscopic studies show that F430 (i.e. the native isomer) is 6-coordinate with long nickel-ligand bonds (approximately 2.1 A), suggesting an approximately planar macrocycle. In contrast, the 12,13-diepimer exhibits a 4-coordinate, square-planar structure with short nickel-nitrogen bonds (approximately 1.9 A), suggesting a ruffled macrocycle. Previous reports, based on other x-ray absorption spectroscopic data, of static disorder in F430 Ni-N distances are shown to be incorrect due to sample heterogeneity. The optical spectrum of F430 (whether purified from the protein-free cytosol or extracted at high ionic strength from the holoenzyme) differs significantly from that of the 12,13-diepimer. The optical spectral differences are correlated with the alterations in coordination number and geometry of the central nickel ion in the two F430 isomers.

Crystal and molecular structure of nitrito-bis(1,3-propanediamine) nickel(II) tetraphenylborate

The title compound is orthorhombic,Mr=590.2,P212121 (No. 19),a=9.865(2),b=9.924(2),c=31.202(7) A,V=3055(2) A3,Z=4,Dx=1.283 g cm−3, λ(MoKα);F(000)=1256; μ(MoKα)=6.76 cm−1, finalR=0.052 for 1441 reflections ∥I≥2.5σ(I)∥. The nitrite group is chelated via the two oxygen atoms; the two six-membered rings resulting from the coordination of the 1,3-propanediamine ligands to the nickel(II) atom are in the chair conformation. The Ni-N and Ni-O distances average 2.07(1) and 2.14(2) A respectively. The two Ni-O distances are nearly equivalent.

A diffraction investigation of some NiTa metallic alloy glasses

X-ray and neutron diffraction measurements have been made on three NiTa metallic glasses, Ni55Ta45, Ni62Ta38 and Ni67Ta33. The total structure factors have been derived and the curves obtained with neutrons found to be particularly well defined. The total radial distribution functions (RDF) obtained are discussed in relation to models of close packing and to the stable crystalline phases in the NiTa alloy system. A derivation of the partial structure factors has been made for the Ni55Ta45 glass by an approximate method. The results of this suggest there is a progressively broadened distribution through the Ni-Ni, Ni-Ta and Ta-Ta first-neighbour distances which allows the form of the first peak in the total RDF to be understood. The broadening and expansion of particularly the Ta-Ta first-neighbour distances in the glassy state is consistent with the kind of local order which exists in the Ni2Ta and mu -NiTa crystalline phases. The possible identification of glassy NiTa alloys as disordered Frank-Kaspar phases, or alternatively as structurally relaxed 'soft sphere' assemblies, is discussed.

Textural and structural studies on nickel hydroxide electrodes: I. Crystallized nickel hydroxide materials submitted to chemical and electrochemical redox cycling

The mechanism of operation of the crystallized nickel(II) hydroxide electrode used in the nickel-cadmium battery is a matter of considerable study and controversy. In this paper particular emphasis is placed on the textural and structural modifications of the phases involved, as a new approach to the chemical and electrochemical redox behaviour of the nickel electrode. X-ray diffraction, electron microscopy and diffraction were performed on two kinds of β(II)-nickel hydroxide materials, during chemical and electrochemical cycling, in an effort to determine the oxidation-reduction mechanism. The existence of important textural modifications was established during the first oxidation cycle. Starting from β(II)-nickel hydroxide with a monolithic texture, it consists in the formation of a mosaic texture. This mosaic texture is preserved during the first reduction and further cycling. A model based on the pseudomorphous and topotactic characteristics of the reactions involved was used to explain the formation of the mosaic texture. The reactions that take place in the solid state by oriented growth of β(III) or γ(III) on β(II) induce strains within the particles; they are due to the large differences in the Ni-Ni distances in the oxidized and reduced phases. Strain relaxation brings about the formation of a mosaic texture, which gives the particles elastic properties that minimize the further strains and make their relaxation easier. The formation of this mosaic texture can be related to the well known forming process of the electrode and its preservation during cycling can be related to the life cycle performance of the system.

Structure of {(1R)-N,N-dimethyl-1-[o-(dicyclohexylphosphino)phenyl]ethylamine}bis(thiocyanato)nickel(II)

Ni(C22Ha6NP)(NCS)2), Mr= 520.38, ortho- rhombic, P212121, a= 15.652(3), b= 15.650(2), c =10.893(1)A, V=2668(1)A 3, Z=4, Din= 1.30 (1), Dx= 1.295 Mg m -3, 2(Mo Ka--) = 0.71069/~, /z--0.954mm -~, F(000)=1104, T=293K, R= 0.058 and wR- 0.060 using 2925 observations with F > a(F). The four-coordinate Ni atom displays tetra- hedrally distorted square-planar geometry with Ni-P and Ni-N(I) distances of 2.190 (1) and 1.974 (4)/~, respectively. The six-membered chelate ring adopts a twist-boat conformation with the methyl substituent of the chiral C atom in an axial position. Introduction. We are investigating the asymmetric hydrosilation (addition of an H-Si bond across a double bond) of prochiral ketones using chiral Rh- aminophosphine species as homogeneous catalysts. In particular, we are interested in the shape of the catalytically active species, as it is thought that the asymmetric environment presented by the catalyst to the incoming substrate molecule is responsible for any optical selectivity observed. The structures of three chiral complexes of Rh containing a norbornadiene ligand and either an aminoarsine (Stephan & Payne, 1982) or an aminophosphine ligand (McKay & Payne, 1985) have been determined. The structure of a chiral dichloropalladium-aminophosphine complex was deter- mined by Takenaka, Sasada, Yamamoto & Tsuji (1977). From these results it became apparent that the conformation adopted by the chelate ring depends strongly upon the metal--donor-atom distance, and probably too upon the steric bulk of the norbornadiene ligand. To confirm this, we required a complex in which the chelate ring size was reduced and the norbornadiene ligand not present. The title compound, (Ni{(R)-o- ( (cyclo-C6Hll)2P) C6H4CHCH3N(CH3)2 } (NC S)2), (Ni(R-dicyphos)(NCS)2), met these criteria, and was prepared by addition of one equivalent of R-dicyphos (1) to a solution of (Ni(NO3)2).6H20 in ethanol followed by addition of five equivalents of NaNCS. The solvent was removed and the complex extracted into a small amount of CH2C12. Addition of ethanol and * To whom correspondence should be addressed.

Studies of Some Tetraazacyclopentadecadiene Complexes of Nickel(II). The Crystal and Molecular-Structure of (1RS,8SR)-(5,7,7,13,15,15-Hexamethyl-1,4,8,12-Tetraazacyclopentadeca-4,1 2-Diene)Nickel(II) Perchlorate Hydrate

The crystal and molecular structure has been determined by X-ray diffractometry for the singlet ground state nickel(II) compound of a fifteen- membered tetraaza macrocyclic ligand , formed by reaction of a mixture of tris ( ethanediamine )nickel(II) and tris (propane-1,3- diamine )nickel(II) perchlorates with acetone. The compound, (1RS,8SR)- 5,7,7,13,15,15-hexamethyl-1,4,8,12-tetraazacyclopentadeca-4,12- diene )nickel(II) perchlorate hydrate, [Ni( hmpd )](ClO4)2.H2O, is monoclinic, space group P21/C, a 1158.76(14), b 1319.53(22), c 1630.35(21) pm, β 96.209(10)°, R 0.046, Rw 0.062 for 2798 reflections. The nickel(II) ion is in tetrahedrally distorted square-planar coordination [mean Ni-N distances 188.9 pm ( imine ), 191.9 pm (amine), displacements of nitrogens c. �20 pm from mean coordination plane]. Triplet ground state compounds [Ni( hmpd )( acac )]ClO4 and [{Ni( hmpd )}2C2O4](ClO4)2, with the macrocycle in folded coordination, were prepared and converted into an isomeric form of [Ni( hmpd )](ClO4)2. The 3,5,7,7,13,15,15-heptamethyl homologue of [Ni( hmpd )]2+ was prepared by reaction of tris (propane-1,2-diamine)- and tris (propane-1,3-diamine)- nickel(II) perchlorates with acetone. The electronic (d-d), 1H N.M.R. and 13C N.M.R . spectra of compounds of these macrocyclic cations, and of (5,5,7,13,15,15-hexamethyl-1,4,8,12-tetraazacyclopentadeca-7,12-diene) nickel(II) are reported.

Crystal and molecular structure ofN-methylphenazinium bis(maleodinitriledithiolato)nickelate(III), [NMP]+ [Ni(mnt)2

The crystal and molecular structure of the title compound, C21H11N6S4Ni, is reported. The crystals are triclinic:P¯1 (No. 2),Z=4,a=8.768(1),b=11.817(3),c=22.131(3) A,α=97.44(1),β=91.90(1), and γ=94.04(1)°. The structure was solved by the heavy-atom method, and refined by full-matrix least squares toR=0.039 for 3213 unique reflections. The Ni atoms of both anions in the asymmetric unit have an approximately square-planar configuration. Anions and cations form segregated stacks alonga. The stacking of the anions along this direction is dimeric, with alternating Ni-Ni distances 4.111(2) and 7.593(2) A for molecule I and 4.208(1) and 8.155(2) A for molecule II. Static susceptibility measurements show strong antiferromagnetic coupling (2J=-241 cm−1) between the two anions of the dimers.

The crystal and molecular structures of the bispyridine and 1,10-phenanthroline adducts of Bis(ethyl 3-mercaptobut-2-enoato)nickel(II)

X-ray analyses of monoclinic crystals of the bispyridine and 1,10-phenanthroline adducts of the monothioacetylacetonate complex bis(ethyl 3-mercaptobut-2-enoato)nickel(n), Ni(eosm)2,* have defined their structures. Crystals of the bispyridine adduct Ni(eosm)2,py2, C22H28N2NiO4S2, belong to the space group P21/c with a 8.865(6), b 15.758(4), c 9.136(3)Ǻ, β 109.18(4)°, Z 2. Crystals of the 1,10-phenanthroline adduct Ni(eosm)2,phen, C24H26N2NiO4S2, belong to the space group P21c with a 12.451(2), b 16.949(1), c 15 5921(2) Ǻ, β 130.97(1)°, Z 4. The structures were refined with diffractometer data measured with Cu Ka radiation to R 0.047 (1962 terms) for the bispyridine adduct and R 0.061 (3115 terms) for the phenanthroline adduct. The geometry about the nickel in each complex is distorted octahedral. The molecule of the bispyridine adduct has exact rn symmetry with the two sulfur atoms cis-equatorial and the nitrogen atoms axial. In the phenan- throline adduct, pairs of sulfur, nitrogen and oxygen atoms are in cis configurations. In the bis-pyridine adduct, the Ni-N bond lengths, 2.153(3) and 2.182(4) Ǻ, are significantly longer than those in other bispyridine adducts of nickel(II) species. It is suggested that the long Ni-N distances reflect the relative instability of the bispyridine adduct, and thermodynamic data are presented to support this.

Neutron diffraction study of the orthorhombic form of [3,3'-dimethyl-3,3'-(2-nitropropanediylidenediamino)bis(2-butanone oximato)-N,N',N'',N''']nickel(II)

A neutron diffraction study of the orthorhombic form of the neutral, monomeric complex [Ni(C13HE~NsOa)] is reported. The compound has eight molecules in the unit cell of symmetry Pbca with a = 13.764 (2), b = 19.978 (4) and c = 11.532 (2)A. The structure was solved by direct methods, and full-matrix least-squares refinement converged to a final R(F) = 0.078. The significant differences between this orthorhombic form and the previously reported, monoclinic form of the complex are in the O.-. O distance and in the twist of the plane of the nitro group with respect to the six-membered chelate ring. In contrast to the reduced precursor, the Ni-N(amine) distances in both forms of this oxidized complex are shorter than the Ni-N(oxime) distances because of the aromaticity of the sixmembered chelate ring. The symmetry-unconstrained intramolecular hydrogen bond is symmetric with one of the shortest O... O distances [2.390 (8)A] observed in the a-amine-oxime metal complexes.

Low-temperature heat-capacity study of Haucke compounds CaNi5, YNi5, LaNi5, and ThNi5

Low-temperature heat capacities of some Haucke compounds (Ca${\mathrm{Ni}}_{5}$, Y${\mathrm{Ni}}_{5}$, La${\mathrm{Ni}}_{5}$, and Th${\mathrm{Ni}}_{5}$) were studied. The electronic specific-heat constants of these compounds are nearly the same and slightly smaller than that of pure nickel. The Deybe temperatures of these compounds show a wider variation than the electronic specific-heat constants. It is found that the lattice rigidity of these four compounds varies considerably, with that of La${\mathrm{Ni}}_{5}$ being the softest, followed by Ca${\mathrm{Ni}}_{5}$, Th${\mathrm{Ni}}_{5}$, and Y${\mathrm{Ni}}_{5}$ in order of increasing rigidity. This appears to influence their hydrogen absorption capacity. The relative softness is correlated with the Ni-Ni distances in the midplane [$3(g)$ sites], and it is suggested that the Ni atoms in this plane play a critical role in governing the hydrogenation behavior of these materials.

Crystallographic and N.M.R.-Relaxation Studies on Bis [{N,N'-(1,3-dimethylpropanediylidene)dianilinato}(1 - )]nickel(II)

A single-crystal X-ray structure determination of bis[{N,N'-(1,3-dimethylpropanediyldene)dianilinato)(1-)]nickel(II) at 295 K shows that, within each of the two independent molecules of the complex within the structure, the nickel atom is chelated by two of the bidentate ligands and is thus four-coordinate. Because of the intramolecular interactions between the phenyl substituents of the ligands, the metal atom environments are highly irregular, although consistent between the two molecules. There are no significant deviations in the Ni-N distances from the mean of 1.965�; but the interligand N-Ni-N angles about the nickel range from 110.4 to 134.7�. A theoretical calculation of the 13C and 1H nuclear relaxation times using the X-ray-determined metal-nuclear separations reproduces the experimentally observed relaxation times for selected positions within the complex, provided ligand-centred effects are taken into account. Mathematical complexity prevents a complete theoretical calculation of the relaxation times for ligand atoms with varying distances from the nickel atom.

Di‐μ‐hydrido‐bis[1,3‐propanbis(dicyclohexylphosphin)]dinickel(NiNi) — Der Bindungszustand in einem Dreizentren‐Wasserstoff‐überbrückten NiNi‐System

AbstractThe crystal structure of the title compound, [(C6H11)2PCH2CH2CH2P(C6H11)2NiH]2 (1), has been determined from 4051 reflections and refined to a final R‐value of 0.044. The positions of the hydrogen atoms (bridging and non‐bridging) have been determined from a difference Fourier synthesis. The molecular structure of the diamagnetic compound consists of subunits doubly‐bridged by hydrogen atoms. The NiNi and average NiH distances are 2.441 and 1.6 Å, respectively. In the solid state the two planes of the P2Ni units form a dihedral angle of 63.3°. Theoretical considerations predict a square‐planar structure for the idealized molecule with a soft potential energy surface for a twisting motion towards the observed geometry. The observed twist is the result of severe intramolecular repulsions between the cyclohexyl groups of the two P2Ni units.

ChemInform Abstract: SYNTHESIS AND CRYSTAL STRUCTURE OF A NOVEL ELECTRON‐RICH NIDO TRIMETALLOCARBORANE

AbstractDie Reaktion von 2‐Carba‐nido‐hexaboran(9) mit Nickelocen und Na‐amalgam in THF führt zu einem Produktengemisch, aus dem das diamagnetische, luftbeständige Trimetallocarboran (I) in niedriger Ausbeute säulenchromatographisch isoliert wird.

Oxidationsprodukt von Bis-(1,2-benzochinondioximato)nickel(II), [Ni(BCD)2], mit Jod: Kristall- und Molekülstruktur

Ni(C6HsN202) 2.10.5, tetragonal, P4/mcc, a= 15553(4), c= 6.307(3) ./~, Z= 4. The structure has been determined by standard methods from single-crystal X-ray diffractometer data and refined by least-squares methods to R=0.095 for 725 independent reflexions. The metal-complex units form columnar stacks with Ni-Ni distances of 3.153(3) A. Iodine chains run parallel to the stacks.