A novel one-dimensional nickel(II) alternating chain from discrete pyrazolate-based dinuclear complexes

Meyer, Franc; Ruschewitz, Uwe; Schober, P.; Antelmann, Björn; Zsolnai, László

doi:10.1039/a708565f

Cited by 34 publications

(32 citation statements)

References 21 publications

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“…[16] Metal···metal separations in all three complexes are very similar and quite short at 4.09 (1a), 4.00 (1b) and 4.11 (2) Å. It should be noted that related nickel(II) chloride complexes of some pyrazolato-derived ligands bearing aliphatic N-donor side arms usually feature five-coordinate nickel atoms, [17] in contrast to the systems studied here. However, close inspection reveals that the Ni-Cl-Ni bridge in 1a is highly asymmetric with a long Ni1-Cl2 distance (2.82 Å) and a much shorter Ni2-Cl2 bond (2.50 Å).…”

Section: Introductionmentioning

confidence: 57%

Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes

et al. 2007

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Four dinickel complexes [L1Ni2(μ‐Cl)(Cl)2]·2CH3OH (1a), [L1Ni2(μ‐Cl)(CH3OH)](ClO4)2 (1b), [L2Ni2(μ‐Cl)Cl2(H2O)2]·H2O (2) and [L3Ni2Cl2(CH3OH)2]Cl·2CH3OH (3) were synthesized and structurally characterized. The ligand scaffolds have a central pyrazolato bridge and N‐donor chelate arms that provide two proximate binding pockets for the nickel ions. While the longer ligand side arms in 1a, 1b and 2 induce Ni···Ni distances of around 4.0 Å and favour incorporation of a chlorido bridge within the dimetallic pocket, a stretched Ni···Ni separation of 4.6 Å with an unusual intramolecular Cl···H–O linkage is observed in 3. Various Cl···H–O hydrogen‐bonding motifs are identified in the solid‐state structures of 1–3, where either the H‐donor (MeOH or H2O) or the H‐acceptor (chlorido) or both are bound to a nickel ion, and their relative donor–acceptor distances are discussed. Magnetic coupling mediated through the pyrazolato and chlorido bridges is rather weak and antiferromagnetic, but it is even weaker for the Cl···H–O linkage. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Introductionmentioning

confidence: 57%

Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes

et al. 2007

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“…It thus transpires that the longer and more flexible ligand side arms in 1 are comparatively more favorable to support an oxidized species than the smaller chelate rings enforced by the shorter side arms in 2, in agreement with previous findings. [25] (with the intensity of the latter increasing at the expense of the former during higher scan numbers), which suggests partial extrusion of water from 2 under the conditions of the MS experiment.…”

Section: Resultsmentioning

confidence: 94%

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

et al. 1999

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Using the possibility of tuning the metal ± metal distance in pyrazolatebased bimetallic complexes by the length of the chelating side arms attached to the heterocycle, we have synthesized related dinickel(ii) complexes in which either a hydroxide (1) or a H 3 O 2 unit (2) spans the two metal centers within the bimetallic pocket. Complex 1 exhibits strong antiferromagnetic coupling mediated by the bridging hydroxide unit (J À 56.9 cm À1 ), while 2 shows Curie ± Weiss behavior over a wide temperature range. The H 3 O 2 unit in 2 acts like the resting form of an active metalbound hydroxide and allows the study of cooperative transformations of small molecules at a dinickel(ii) site relevant to the active site of the metalloenzyme urease. Firstly, it mediates the hydration of various nitriles to give the respective m-amidato-N,O-bridged complexes 3 a ± c. Reaction of 2 with urea affords complex 5 with an N,O-bridging deprotonated urea, which when heated releases ammonia to yield the cyanato-bridged dinickel(ii) compound 4. This product is also obtained when 2 is treated with dimethylcyanamide. Unactivated amides dimethylformamide (DMF) and dimethylamide (DMA) are hydrolyzed by 2 only sluggishly, while the stoichiometric hydrolysis of esters such as ethyl acetate and ethyl propionate runs more cleanly to afford the carboxylato-bridged bimetallic complexes 10 b and c. Likewise, hydrolytic cleavage occurs with g-butyrolactone to give complex 10 d. We propose that these reactions proceed by cooperative action of the two metal ions within the bimetallic pocket of the dinickel(ii) core. Possible alternatives are addressed by investigation of analogous mononuclear nickel(ii) complexes 8 a and b in conjunction with a corresponding dimeric compound 9 and by the reaction of 2 with an excess of acetate to yield the dinickel(ii) complex 11, in which a formerly chelating side arm has been driven out of the coordination sphere. Complexes 1´(BPh 4 ) 2 , 2( BPh 4 ) 2 , 3c´(ClO 4 ) 2 , 4´(BPh 4 ) 2 , 8 b( ClO 4 ) 2 , 9´(ClO 4 ) 2 , 10 d´(ClO 4 ) 2 , and 11´(ClO 4 ) have been characterized structurally by X-ray crystallography.

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“…Following this approach, we have recently reported first examples of novel nickel(II) alternating chains that are assembled in a targeted manner from pyrazolate-based dinickel(II) building blocks and additional chloro or azido bridges. [26,27] We have now exploited this approach in a broader sense, and we analyze the magnetic properties of the new HABAs by Quantum Monte Carlo (QMC) simulations. Monte Carlo methods are increasingly used as a tool to evaluate magnetic properties, [28] but they remain simple only in the case of the Ising model and the classical spin approximation.…”

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confidence: 99%

Alternating Spin Chains: Controlled Assembly from Bimetallic Building Blocks and QMC Simulation of Spin Correlation

Demeshko¹,

Leibeling²,

Dechert³

et al. 2007

ChemPhysChem

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By using the compartmental dinucleating pyrazolate ligand HL, dinickel(II) complexes [LNi2(micro-N3)(acetone)2]X2 (1: X = CIO4; 2: X = BPh4) and tetranickel(II) complex [{LNi2(micro-N3)(MeOH)2](CI04)4 (3) have been prepared and structurally characterized. Complexes 1 and 2 differ in the torsion along the bridging micro-1,3-azide moiety, while the azido ligands in 3 adopt an unusual micro-1,1,3 bridging mode to connect the two subunits. All three complexes show overall antiferromagnetic coupling and an S = 0 ground state, but the torsion along the azide moiety is a determining factor for the coupling strength. Compounds 1 and 2 serve as preorganized building blocks for the controlled synthesis of alternating 1D polymeric structures 4-6 by replacement of their labile acetone ligands by additional azido ligands. Due to the modular synthetic approach, 4-6 can be described as Heisenberg antiferromagnetic systems with inherent bond alternation (HABA), whereby the organic ligand framework ensures that the individual nickel/azido chains are well isolated in the crystal lattice. Like their precursors, 4-6 are mainly distinguished by torsion along the micro-1,3-azido bridges, both within and between the bimetallic constituents. Magnetic measurements confirm an overall 5 = 0 ground state for 4-6, and coupling parameters have been deduced from quantum Monte Carlo simulations. The two J values for the alternating 1D chains can be clearly assigned on the basis of the magnetostructural correlations established for the bimetallic building blocks. The alternation ratio gamma = J2J1(-1) places the three new systems in the HABA regime for a singlet-dimer ground state.

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A novel one-dimensional nickel(II) alternating chain from discrete pyrazolate-based dinuclear complexes

Cited by 34 publications

References 21 publications

Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes

Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes

Cooperative Transformations of Small Molecules at a Dinuclear Nickel(II) Site

Alternating Spin Chains: Controlled Assembly from Bimetallic Building Blocks and QMC Simulation of Spin Correlation

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