Diamagnetic Nickel Complexes Research Articles

New Ni(II)-Ni(II) Dinuclear Complex, a Resting State of the (α-diimine)NiBr2/AlMe3 Catalyst System for Ethylene Polymerization

A novel room-temperature stable diamagnetic nickel complex 2 was detected upon activation of Brookhart-type ethylene polymerization pre-catalyst LNiBr2 (1, L = 1,4-bis-2,4,6-trimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) with AlMe3. Using in situ 1H, 2H, and 13C NMR spectroscopy, as well as DFT calculations, this species has been identified as an antiferromagnetically coupled homodinuclear complex [LNiII(μ-Me)(μ-CH2)NiIIL]+Br−. Its behavior in the reaction solution is characteristic of the resting state of nickel catalyzed ethylene polymerization.

Bis(1,2-dithiosquarato)nickelates(II) – Synthesis, Structure, EPR and Thermal Behavior

1,2-Dithiosquaratonickelates are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. The synthesis and characterization, including mass spectrometry, of a series 1,2-dithiosquaratonickelates(II), [Ni(dtsq)2]2-, with several "onium" cations is reported and the X-ray structures of two diamagnetic complexes, (HexPh3N)2[Ni(dtsq)2] and (BuPh3N2[Ni(dtsq)2] with sterically demanding counter ions are presented. The diamagnetic nickel complexes have been doped as host lattices with traces of Cu(II) to measure EPR for additional structural information. The thermal behavior of this series is studied by thermogravimetry and differential thermo analysis (TG/DTA). The thermolysis in air as well as under nitrogen atmosphere of these complexes results in nickel oxide nano-particles in all cases, which are characterized by X-ray powder diffraction.

Theoretical evidence for the singlet diradical character of square planar nickel complexes containing two o-semiquinonato type ligands.

Density functional theory and complete active space self-consistent field computations are applied to elucidate the singlet diradical character of square planar, diamagnetic nickel complexes that contain two bidentate ligands derived from o-catecholates, o-phenylenediamines, o-benzodithiolates, o-aminophenolates, and o-aminothiophenolates. In the density functional framework, the singlet diradical character is discussed within the broken symmetry formalism. The singlet-triplet energy gaps, the energy gained from symmetry breaking, the spin distribution in the lowest triplet state, and the form of the magnetic orbitals are applied as indicators for the singlet diradical character. Moreover, a new index for the diradical character is proposed that is based on symmetry breaking. All symmetry breaking criteria show that the complexes obtained from o-catecholates and o-benzodithiolates have the largest and the smallest singlet diradical character, respectively. The singlet diradical character should be intermediate for the complexes derived from o-phenylenediamines, o-aminophenolates, and o-aminothiophenolates. The diradical character of all complexes suggests the presence of Ni(II) central atoms. This is also indicated by the d-populations computed by means of the natural population analysis.

Chemical and antifungal properties of the nickel(II) complexes of 2-formylpyridine4 N-methyl-,4 N-dimethyl-,4 N-diethyl- and4 N-dipropylthiosemicarbazones

Nickel(II) complexes of 2-formylpyridine4N-methyl-,4N-dimethyl-,4N-diethyl- and4N-dipropylthiosemicarbazones having approximately octahedral, planar and tetrahedral stereochemistry have been prepared and characterized spectroscopically.1H-n.m.r. of the thiosemicarbazones and a diamagnetic nickel complex are reported as well as the thiosemicarbazones’13C-n.m.r. spectra. The nickel(II) complexes show no growth inhibitory activity againstAspergillus niger, but have considerable activity againstPaecilomyces variotii, decreasing with increasing size of the ligand.

Polytertiary phosphines and arsines. 19. Some first-row transition metal chloride complexes of ditertiary and tritertiary phosphines containing terminal methoxy groups

The triphosphines RP[CH 2CH 2P(OCH 3) 2] 2 (R = CH 3 and C 6H 5) react with the metal(II) chlorides of iron, cobalt, and nickel in methanol solution to form the corresponding [(triphos)MCl] + cations isolated as the chloride and hexafluorophosphate salts. Magnetic susceptibility data indicate that the yellow diamagnetic nickel complexes are square planar but the blue to green cobalt and brown iron complexes are tetrahedral. Nickel(II) chloride reacts with the diphosphine (C 6H 5) 2PCH 2CH 2P(OCH 3) 2 to give a diamagnetic apparently square planar nickel(II) complex of the stoichiometry (diphos) 2NiCl 2 in which each diphosphine unit functions as a monodentate ligand. However, cobalt(II) and iron(II) chlorides react with (C 6H 5) 2PCH 2CH 2P(OCH 3) 2 to give products of stoichiometry (diphos)MCl 2 formulated as the dimeric ionic derivatives [(diphos) 2M 2Cl 2]Cl 2 on the basis of magnetic measurements, conductivities, and metathesis with NH 4PF 6.

Deactivation of singlet oxygen and triplet pentacene by transition metal complexes

Rate constants, kQ, have been determined for the deactivation of singlet oxygen in carbon tetrachloride by a range of transition metal complexes. The singlet oxygen was produced by flash photolysis of air-saturated carbon tetrachloride solutions with methylene blue as sensitizer, and the decay followed by observing the concentration of the accepter 1,3-diphenyliso-benzofuran at 435 nm. The high rate constants of certain diamagnetic nickel complexes are accounted for by a spin-allowed transfer of electronic energy from singlet oxygen to the complex. Rate constants have also been determined for the deactivation of triplet pentacene by a number of these metal complexes. The triplet pentacene was produced by flash photolysis of dilute solutions of pentacene in benzene and the decay monitored at 492 nm. The rate constants for quenching of triplet pentacene are generally lower than those for quenching of singlet oxygen but there is a good correlation between the two sets of results. Both processes appear to proceed by way of electronic energy transfer without the intervention of complex formation between donor and accepter.

Coordination chemistry of benzothiazole derivatives. 2-mercaptobenzothiazole and 2-(o-hydroxyphenyl)benzothiazole complexes with Cu(II), Ni(II) and Co(II)

Abstract The reaction of 2-mercaptobenzothiazole (MBTH) with Cu(II) ions resulted in a yellow diamagnetic Cu(II) complex, while the reaction with Co(II) produced a dimeric tetrahedral complex. The reaction of Ni(II) with MBTH gave a diamagnetic square planar complex. The yellow copper complex formed a blue five coordinate dimeric complex with pyridine. The isolated blue crystals were investigated by electron spin resonances. The reaction of the diamagnetic nickel complex with different bases yielded distorted octahedral dibase adducts. 2-( o -hydroxyphenyl)benzothiazole gave a brown pseudo tetrahedral complex with Cu(II) and a distorted tetrahedral complex wiht Ni(II). The reaction with Co(II) produced a high spin five coordinate polymeric type compound. The solid spectra of the complexes as well as their base adducts were investigated.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g∥ = 2.085, g⊥ = 2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu ∞ 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu–S bonds. The experimentally determined hyperfine constants are A 1s = 34.9 × 10−4 cm−1, B 1s = 26.1 × 10−4 cm−1, A 2s = 60.4 × 10−4 cm−1, B2s = 55.5 × 10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the σ bond, the π bonds are also strongly covalent.

Application of the angular overlap model to the interpretation of the electronic spectra of some copper(II) and nickel(II) acetylacetonate complexes

The angular overlap model has been used to calculate σ- and π;-bonding parameters for three copper complexes and one nickel complex of the type M(acac)2(acac = the acetylacetonate anion or a closely related ligand). The results suggest that the orbital energy sequence in the copper complexes is probably dxydz2 > dx2–y2 > dxz∼dyz, but that in the nickel complex the stronger metal-ligand interaction causes the sequence dxydx2–y2 > dz2 > dxz∼dyz. The parameters estimated for the diamagnetic nickel complex can successfully be used to predict the d-orbital splittings observed for three paramagnetic nickel acetylacetonate complexes.

Two modes of chelation in Bis(4-iminopentane-2,3-dione 3-oximato)nickel(II)

The red, neutral, diamagnetic nickel complex formed by the reaction of bis(pentane-2,4-dionato)nickel(II) with nitrite and ammonium ions has been investigated by p.m.r., infrared, and mass spectrometry. It is proposed that this complex has a novel unsymmetrical structure in which the ligand [CH3COC(NO)C(NH)CH3]- exhibits two different modes of chelation in the same molecule. The modes differ in that an oximino nitrogen-to-nickel bond in one chelate ring is replaced by an oximino oxygen-to-nickel bond in the other. 2H-, 15N-, and 18O-labelled derivatives of the complex have been prepared and the isotopic shifts observed in the infrared spectra have been used to assign particular vibrational modes. An analogous unsymmetrical structure is also proposed for bis(1-ethoxyoarbonyl-2-iminopropan-1-one oximato)nickel(II).

The Absorption Spectra of Para- and Diamagnetic Nickel Complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Absorption Spectra of Para- and Diamagnetic Nickel ComplexesJ. E. Mills and D. P. MellorCite this: J. Am. Chem. Soc. 1942, 64, 1, 181–182Publication Date (Print):January 1, 1942Publication History Published online1 May 2002Published inissue 1 January 1942https://doi.org/10.1021/ja01253a507RIGHTS & PERMISSIONSArticle Views92Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (236 KB) Get e-Alerts Get e-Alerts

A Magnetic Study of the Effect of Bond Angle Distortion

THE prediction1 that diamagnetic nickel complexes would prove to be square co-ordinated has been verified in a number of different ways. The discovery of isomeric nickel glyoximes2, the crystal structure of potassium nickel dithioxalate3 and investigations of crystal optics4 and isomorphism5 of other diamagnetic nickel compounds have all borne out the existence of this correlation between structure and magnetic properties. All internal nickel complexes in which four nitrogen atoms are bonded to the metal atom have proved, on investigation, to be diamagnetic, and they may therefore be presumed to be square bonded. The nickel derivatives of various glyoximes2, phthalocyanine6 and proto-porphyrin7 afford examples of this type of complex. In these circumstances it becomes possible to investigate magnetically the question as to whether distortion from a square configuration gives nickel-nitrogen bonds sufficient ionic character to make a complex paramagnetic.

33. The planar configuration of diamagnetic nickel complexes. Part I. Isomeric nickel derivatives of benzylmethylglyoxime

33. The planar configuration of diamagnetic nickel complexes. Part I. Isomeric nickel derivatives of benzylmethylglyoxime