Square-planar Nickel Research Articles

Structure and O2 uptake properties of a novel nickel(II) complex of pyridyl-pendant dioxocyclam [1-(2-pyridyl)methyl-5,7-dioxo-1,4,8,11-tetraazacyclotetradecane

Novel potentially five-coordinate pyridyl–pendant dioxocyclam [1-(2-pyridyl)methyl-5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (H2L) and its homologs (6-methyl and 6,6-dimethyl derivatives)] have been synthesized to study nickel(II) complexation. A purple nickel(II) complex with a deprotonated amide (NiHL) was isolated from aqueous equimolar solution of H2L and Ni(ClO4)2. A yellow nickel(II) complex with two deprotonated amides (NiL) was crystallized from an H2O/CH3CN solution of H2L and Ni(OH)2. The X-ray crystal study of NiL showed a square-planar nickel(II) complex with the pyridyl–pendant remaining uncoordinated. It is concluded from the visible absorption and NMR study of NiL in aqueous solution that the four-coordinate NiL is in equilibrium with a five-coordinate square-pyramidal nickel(II) complex with the apical coordination of the pyridyl–pendant. A voltammetric study disclosed a low nickel(II/III) redox potential of +0.29 V vs SCE for NiL at pH 9.5 and 25 °C with 0.10 M Na2SO4. The nickel(II) complex NiL absorbed an equimolar amount of O2 at pH 9.5 and 25 °C, and the O2 was activated to cleave plasmid DNA.

Synthesis, crystal structure and equilibrium studies on bidentate amine adducts of bis(S-benzyl)-β-N-(4-dimethylaminobenzyl)methylendithiocarbazone nickel(II) complex

The novel adducts of chelating diamines to the diamagnetic, square-planar nickel(II) complex bis(S-benzyl)-β-N-(4-dimethylaminobenzyl)methylendithiocarbazone nickel(II) [hereafter abbreviated Ni(SN) 2] have been prepared and characterized, where the chelating diamines are 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), 5-nitro-1, 10-phenanthroline (NO 2phen), 4,4′-methyl-2,2′-bipyridine (Mebipy) and 4,5-diazafluren-9-one (diafo). The addition equilibrium constants ( K), determined by a UV-vis spectrometer, were influenced by the coordinating ability of the added ligands in the order: K phen > K mebipy > K bipy > K NO 2phen > K diafo. The single crystal structure of the phenanthroline adduct was determined to study the possible mechanism of the addition processes. The coordination geometry of the nickel atom is distorted octahedral The four nitrogen atoms of the two SN ligands and the phenanthroline molecule form the equatorial plane with a NiN distance ca 2.10 Å and the two sulfur atoms site at the axial positions with the NiS distance of 2.40 Å. From the results of structural determination and the addition equilibrium studies, the possible addition mechanisms have been discussed.

Neutral and cationic nickel(II) complexes of phosphino-amines: [NiCl 2(PMe 2Ph) (PNMe 2)] and [NiCl(PMe 2Ph) (PNMe 2)] PF 6 (PNMe 2 = N, N′-dimethyl-2-(diphenylphosphino)aniline)

A neutral bidentate P,N-ligand combining a hard dimethylamino nitrogen and a soft phosphine phosphorus donor affords the neutral trigonal bipyramidal as well as the cationic square-planar nickel(II) complexes cis-[NiCl 2(PMe 2Ph)(PNMe 2)] and [NiCl(PMe 2Ph)(PNMe 2)]PF 6, respectively. The latter species exhibits an appreciable catalytic activity in propylene oligomerization in the presence of Et 2AlCl as co-catalyst

Synthesis and crystal structure of [Ni{Ph2PC(S)NPh}2] and [Ni{Ph2P(Y)C(S)NPh}2](Y = S or Se)

The square-planar nickel(II) complexes [Ni{Ph2PC(S)NPh}2] and [Ni{Ph2P(Y)C(S)NPh}2](Y = S or Se) have been prepared and characterised spectroscopically. Their structures have been confirmed by single-crystal X-ray diffraction methods. In [Ni{Ph2PC(S)NPh}2] the Ni atom is chelated by the thioamide S atoms [2.188(2), 2.163(2)A] and phosphine P atoms [2.171(2), 2.182(2)A] which define a trans-S2P2 donor set. In [Ni{Ph2P(S)C(S)NPh}2] the centrosymmetric structure features S,S chelating ligands with the Ni–S (thioamide) distance of 2.184(2)A being equivalent to the Ni–S (sulfide) distance of 2.197(2)A in the S4 donor set. In [Ni{Ph2P(Se)C(S)NPh}2] the Ni atom in the centrosymmetric structure exists in a square-planar S2Se2 donor set with Ni–S 2.202(3)A and Ni–Se 2.344(1)A.

Oxidative dehydrogenation of a saturated tetraaza macrocyclic nickel(II) complex: selective formation of nickel(II) complexes containing one or two imino groups

The reaction of the saturated polyaza macrocyclic nickel(II) complex [NiL1][ClO4]2(L1= C-meso-3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12] docosane) with concentrated HNO3 in water–methanol (1 : 1) solution yielded the low-spin nickel(III) complex [NiL1(NO3)2]ClO4. The latter is further oxidized in the presence of the acid to produce the diimine complex [NiL2]2+(L2= 3,14-dimethyl-2,6,13,17-tetraazatricyclo-[16.4.0.07.12]docosa-2,13-diene). The monoimine complex [NiL3][ClO4]2(L3= C-meso-3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12] docos-5-ene) can also be prepared by the oxidative dehydrogenation reaction of [NiL1]2+ with HNO3 in water–acetonitrile (1 : 1) solution. The square-planar nickel(II) complexes of L2 and L3 were characterized. The crystal structure of [NiL3][ClO4]2 shows that the complex has a somewhat distorted square-planar geometry.

Formation of a nickel(II) complex with a new N2S2macrocyclic ligand by C–Cl bond cleavage and C–S bond formation

Heating a monohelical square-planar nickel(II) complex containing chlorine atoms in the side arms gives a distorted octahedral nickel(II) complex containing the trans-N2S2 macrocyclic ligand by carbon–chlorine bond cleavage and carbon–sulfur bond formation.

A functional nickel(II) complex carrier for up-hill transport of a histidine derivative by pH-induced affinity switching

The square-planar nickel(II) complex of 6,6-bis(4-hexylbenzoylamino)-2,2′-bipyridine mediates up-hill transport of carbobenzoxyhistidine (Cbz-His) across an organic liquid membrane by affinity switching of the axial coordination of the imidazole unit of Cbz-His to the metal centre.

Interactions of nickel(II) with histones. Stability and solution structure of complexes with CH3CO-Cys-Ala-Ile-His-NH2, a putative metal binding sequence of histone H3.

Nickel(II) compounds are established human carcinogens, but the molecular mechanisms underlying their activity are only partially known. One mechanism may include mediation by nickel of promutagenic oxidative DNA damage that depends on Ni(II) binding to chromatin. To characterize such binding at the histone moiety of chromatin, we synthesized the peptide CH3CO-Cys-Ala-Ile-His-NH2 (L), a model of the evolutionarily conserved motif in histone H3 with expected affinity for transition metals, and evaluated its reactivity toward Ni(II). Combined spectroscopic (UV/vis, CD, NMR) and potentiometric measurements showed that, at physiological pH, mixtures of Ni(II) and L yielded unusual macrochelate complexes, NiL and NiL2, in which the metal cation was bound through Cys and His side chains in a square-planar arrangement. Above pH 9, a NiH-3L complex was formed, structurally analogous to typical square-planar nickel complexes. These complexes are expected to catalyze oxidation reactions, and therefore, coordination of Ni(II) by the L motif in core histone H3 may be a key event in oxidative DNA base damage observed in the process of Ni(II)-induced carcinogenesis.

Cooperative interactions between ions and water in the chloride ion and water coordination to a square-planar nickel complex ion in concentrated aqueous solutions

In concentrated aqueous solutions (1–6 mol dm–3) of various kinds of salts such as sodium chloride, calcium chloride, tetramethylammonium chloride and sodium perchlorate, salt effects on coordination of the chloride ion and water to [Ni(tmc)]2+(tmc: 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) have been investigated spectrophotometrically. In water at 25 °C 63% of the nickel complex is coordinated by water as a five-coordinate species. Addition of perchlorates to the complex solution decreases the fraction of the five-coordinate complex without shifting the absorption peaks and 6.5 mol dm–3 perchlorate gives 100% of the four-coordinate species. With sodium chloride, the fraction of the four-coordinate species is increased with concomitant red shifts in wavelength and decreases in absorbance at the absorption peaks for the five-coordinate species. On the other hand, tetramethylammonium chloride decreases the fraction of the four-coordinate species with similar red shifts of the five-coordinate peaks. The red shift is attributed to coordination of the chloride ion. The different effect caused by sodium chloride compared with tetramethylammonium chloride is discussed in terms of the difference in cooperative interactions between the chloride ion and the counter-cations through hydrated water molecules.

Syntheses of square-planar nickel-(II) and -(I) complexes of an octaaza macrohexacyclic ligand and crystal structure of the nickel(II) complex

Download options Please wait... Article information DOI https://doi.org/10.1039/DT9940002765 Article type Paper Download Citation J. Chem. Soc., Dalton Trans., 1994, 2765-2769 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Syntheses of square-planar nickel-(II) and -(I) complexes of an octaaza macrohexacyclic ligand and crystal structure of the nickel(II) complex M. P. Suh, I. S. Kim, S. Cho and W. Shin, J. Chem. Soc., Dalton Trans., 1994, 2765 DOI: 10.1039/DT9940002765 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Myunghyun Paik Suh Il Soon Kim Seung-Je Cho Whanchul Shin

Synthesis, characterization and structure of the highly sterically congested complex (3,14-dimethyl-14-nitromethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docos-2-ene)nickel diperchlorate and structure of (3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosa-2,13-diene)nickel diperchlorate

The reaction of the diimine complex [NiL1][ClO4]2(L1= 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosa-2,13-diene), containing cyclohexane subunits fused to the five-membered chelate rings, with nitromethane in the presence of triethylamine produced the highly sterically congested complex [NiL2][ClO4]2(L2= 3,14-dimethyl-14-nitromethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docos-2-ene) containing one nitromethyl pendant arm. The electronic spectrum of [NiL2]2+ in nitromethane solution shows the d–d band at ca. 490 nm (Iµ= 170 dm3 mol–1 cm–1). The wavelength and the molar absorption coefficient are extraordinarily longer and larger, respectively, than those for square-planar nickel(II) complexes of L1 and other related 14-membered polyaza macrocycles. The crystal structures of [NiL1][ClO4]2 and [NiL2][ClO4]2 revealed that the former has normal square-planar geometry with the nickel atom lying on the N4 plane, whereas the latter has a severely distorted square-planar geometry with the metal atom 0.118 A out of the mean plane of the donor nitrogen atoms. The steric effects of the substituents of the complexes on the geometry and the spectra are discussed. Crystal data: for [NiL1][ClO4]2, monoclinic, space group P21/n, a= 10.423(3), b= 8.9375(6), c= 13.457(3)A, β= 94.459(12)°, Z= 2, R= 0.056 and R′= 0.057 for 2349 independent reflections with Fo2 > 3σ(Fo2); for [NiL2][ClO4]2, monoclinic, space group P21/n, a= 11.968(3), b= 12.6208(14), c= 19.358(6)A, β= 105.008(1 5)°, Z= 4, R= 0.046 and R′= 0.045 for 3382 independent reflections with Fo2 > 3σ(Fo2).

Structure and reactivity of aryl(bromo)nickel complexes relevant to nickel(0) complex-promoted dehalogenative polycondensation of organic dihalides

Reactions of 4-bromobiphenyl, 1,4-dibromobenzene, and 9,10-dibromoanthracene with [Ni(cod)2](cod = cycloocta-1,5-diene) in the presence of PEt3 gave arylnickel complexes, tans-[NiBr(C6H4C6H5)(PEt3)2]1, trans-[NiBr(C6H4Br-p)(PEt3)2]2, and trans-[NiBr(C14H8Br)(PEt3)2]3, respectively. 4,4′-Dibromobiphenyl reacted with a [Ni(cod)2]–PEt3 mixture to give trans, trans-[(Et3P)2BrNi(C6H4C6H4)NiBr(PEt3)2]4. The structures of complexes 1–4 with trans configuration around square-planar nickel centres have been determined by X-ray crystallography. The NMR (1H, 13C, and 31P) spectra of the complexes are consistent with the trans structures. Complexes 2 and trans-[NiBr(Ph)(PEt3)2]5 did not undergo any thermal reaction at 60 °C in dimethylformamide. Complex 2 reacted with Mel at room temperature to give a mixture of p-bromotoluene (17%) and 4,4′-dibromobiphenyl (8%), while similar reaction of 5 gave a mixture of toluene (15%) and biphenyl (78%). Reaction of complex 4 with Mel gave 4-methylbiphenyl and quaterphenyl.

Thermodynamic and structural study of coordination of the monodentate ligand ammonia in a square-planar nickel(II) complex with a tridentate amine

The octahedral nickel(II) complex of the tridentate ligand dachen ( N-(2-aminoethyl)-1,4-diazacycloheptane), Ni(dachen)(H 2O) 3] 2+, reacts with ammonia to yield the square-planar complex [Ni(dachen)(NH 3)] 2+, a rare example of coordination of the monodentate ammine ligand in a low-spin nickel(Il) complex. The structure of Ni(dachen)(NH 3)](ClO 4) 2 was determined by X-ray diffraction. Crystal data: orthorhombic space group Pbca, a= 13.402(3), b= 13.625(4), c= 17.118(4) Å, V= 3125.8(16) Å 3, Z=8. The structure was solved by direct methods and was refined to R = 0.053. The stability constant of [Ni(dachen)(NH 3)] 2+ was determined by a spectrophotometric method. The log K value for addition of ammonia to [Ni(dachen)(H 2O) 3] 2+ to form square-planar Ni(dachen)(NH 3)] 2+ was found to be 3.3 ±0.1, an estimated 1.6 log units greater than for binding of ammonia in an analogous high-spin nickel(Il) complex.

A square-planar NiS4unit with an aliphatic thiolato–thioether donor set: a carbon monoxide dehydrogenase model that binds CO

Ni+–CO was generated by using a newly prepared square-planar nickel compound with an aliphatic thiolato–thioether sulfur ligand, with relevance to the nickel centre of carbon monoxide dehydrogenase.

Copper and nickel complexes of 1,8-disubstituted derivatives of 1,4,8,11-tetraazacyclotetradecane

The stereoselective synthesis of various 1,8-disubstituted derivatives of 1,4,8,11-tetraazacyclotetradecane (cyclam) has been achieved and copper and nickel complexes prepared. For the 1,8-dibutyl derivative, the square-planar nickel(II) complex exists as two diastereoisomers, as revealed by crystallographic analysis. The structure of the copper(II) complex of this ligand confirmed that a strong in-plane ligand field was conserved in square-planar complexes notwithstanding the dialkylation at nitrogen. The structures of the copper(II) complexes of two 1,8-dicarboxymethyl derivatives of cyclam also reveal primary N4 co-ordination with carboxyl oxygens occupying the elongated axial sites. The tricyclic ligand 1,5,8,12-tetraazatricyclo[10.2.2.25,8]octadecane is readily prepared from one of these diacids and the copper complex is kinetically stable in solution with respect to attack by hydrogen sulfide and to acid-catalysed dissociation.

Catalytic dimerization of ethylene to 1-butene by square-planar nickel complexes

The dimerization of ethylene by [NiBr(2,4,6-Me3C6H2)P2] (PPEt3, PMe2Ph, PPh3, P(Bu)3, P(i-Bu)3, PCy3, and PBz3 (Bzbenzyl)) and [Ni(2,4,6-Me3C6H2)(NCMe)P2]BF4 (PPEt3, PMe2Ph, P(Bu)3, P(i-Bu)3, and PBz3) in THF solution has been investigated. With ionic compounds, only butenes are formed with very high selectivity to 1-butene (90%). Activity increases with the basicity and size of the phosphine ligands. Ionic compounds are always more active than the neutral precursors for the same phosphine. The ionic compound [Ni(2,4,6-Me3C6H2)(NCMe)(PBz3)2]BF4 shows the highest turnover rate (0.7 s−1).

A square-planar nickel(III) complex of an innocent ligand system

A square-planar nickel(III) complex of an innocent ligand system

Kinetics and mechanism of formation of square-planar copper(II) and nickel(II) complexes of ethylenebisbiguanide in aqueous acetate buffer media

The kinetics of formation of square-planar CuII and NiII complexes of the quadridentate ligand, ethylenebisbiguanide, have been studied spectrophotometrically in aqueous HOAc−NaOAc buffer, at ionic strength 0.2 mol dm−3, in the 25–35°C temperature range. The observed rate constants for the formation reactions are independent of pH (and of OAc− concentration) in the pH range used (3.6–4.8 for CuII and 5.0–5.8 for NiII) where the product complexes form stoichiometrically, but show first-order dependence on the ligand concentration;i.e. kobs=kf[L]total. At 25°C kf values (dm3 mol−1s−1) are 35.2±0.4 for CuII and (8.4±0.1)×10−3 for NiII. The mechanism of the reactions is discussed.

High turnover rates in pH-dependent alkene epoxidation using NaOCl and square-planar nickel(II) catalysts

Transition-metal-catalyzed transfer of oxygen atoms to organic substrates is of interest in the study of bioinorganic mechanisms and the development of efficient catalysts for laboratory and industrial organic synthesis. Certain nickel(II) catalysts have recently joined the plethora of metalloporphyrin complexes capable of facilitating this reaction using OCl{sup {minus}}, PhIO, or KHSO{sub 5} as terminal oxidant. Here, we report an unusual pH dependence of the OCl{sup {minus}}-based reactions which leads to dramatic rate accelerations in olefin epoxidation at reduced pH.

Synthesis of chiral atropoisomeric square-planar nickel(II) and copper(II) complexes formed by macrocyclic ligands containing pendant polyether groups and a quaternary ammonium group

Novel copper(II) and nickel(II) complexes of macrocyclic Schiff bases formed from derivatives of N,N′-bis(2-benzoylphenyl)oxamide and 1,2-diaminoethane have been prepared. In one case, separation of atropoisomeric chiral complexes has been achieved by preparative chromatography on SiO2. Quaternization of some of the complexes with an excess of MeI affords chiral complexes possessing a positively charged quaternary ammonium group and polyether podands in addition to a weakly electrophilic metal site.