Octahedral–Tetrahedral Systems [Co(dppmO,O)3]2+[CoX4]2– Showing Slow Magnetic Relaxation with Two Relaxation Modes

Varga, Filip; Titiš, Ján; Moncóľ, Ján; Boča, Roman

doi:10.1021/acs.inorgchem.7b03193

Cited by 19 publications

(7 citation statements)

References 37 publications

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“…In a number of cases it was attributed to the same paramagnetic center. 29 And there are few examples of complexes of Co 2+ , [30][31][32][33][34] Ni 2+ , 35 and Cu 2+ , 36 where the slower relaxation path shows weak temperature dependence like in our case. A slow decrease with increasing temperature may even turn back to a weak increase of s at higher temperatures.…”

Section: Relaxation Of Magnetizationmentioning

confidence: 47%

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

et al. 2020

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Section: Relaxation Of Magnetizationmentioning

confidence: 47%

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

et al. 2020

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“…Owing to the poor coordinating ability of triflate, the greater ionization of Zn(OTf) 2 in MeCN as compared to that of ZnI 2 is likely the cause of the observed rate enhancement. It has been documented that anionic species such as [ZnI 4 ] 2– will readily form in the presence of a well-chelated, cationic transition-metal complex, and we believe a similar iodide-scavenging process is operative in the present case (vide infra). , Salt additives have been shown to enhance the rate of other Ni-catalyzed cross-couplings …”

Section: Results and Discussionmentioning

confidence: 52%

Identifying the Imperative Role of Metal–Olefin Interactions in Catalytic C–O Reductive Elimination from Nickel(II)

et al. 2021

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We present a series of experimental and computational mechanistic investigations of an unusually facile example of Ni-catalyzed C–O bond formation. Our method, originally reported in 2016, involves the formation of cyclic enol ethers from vinyl iodides bearing pendant alcohol groups. Our findings suggest that the observed reactivity arises from the coordination of the olefin in the vinyl iodide starting material and the enol ether product with Ni(0) intermediates. Density functional theory calculations reveal a plausible catalytic mechanism involving a Ni(II)/Ni(0) redox cycle featuring two-electron C–I oxidative addition and C–O reductive elimination steps. The direct formation of a η2-enol ether Ni(0) complex from a key Ni(II) alkoxide intermediate dramatically alters the free energy (ΔG) for the vinyl C–O reductive elimination step relative to other examples of C–O reductive elimination at Ni(II). Furthermore, efficient σ-π mixing in the course of vinyl C–O reductive elimination leads to lower computed kinetic barriers (ΔG ‡) relative to those of aryl C–O reductive elimination. The conclusions drawn from these computational models are supported by synthetic organometallic experiments, whereby a vinyl–Ni(II) iodide intermediate was isolated, characterized, and proved to yield enol ether, following exposure to triethylamine. We conducted further experiments and computations, which indicated that the two-electron oxidative addition of vinyl iodides by Ni(0) depends on the formation of an η2-vinyl iodide precomplex, based on the observation of one-electron activation of the same vinyl iodide in the presence of sterically encumbering ligands (e.g., tricyclohexylphosphine).

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“…Thus, in order to minimize the probability of the quantum relaxation pathway in zero dc field and to estimate the energy barrier accurately, the ac susceptibility was measured under different dc fields. It is worth mentioning that no slow relaxation of magnetization was detected in the case of complex 1 from ac susceptibility measurements even by using a 6000 Oe dc magnetic field (Figure S21), although slow relaxation of magnetization has recently been reported in [Co(N3) 2 ][Co(NCS) 4 ] (N3 = tridentate N-donor ligand) types of complexes as well as in the [Co(NCS) 4 ] 2– unit with different metal cation complexes. − …”

Section: Results and Discussionmentioning

confidence: 97%

Effect of Coordination Geometry on Magnetic Properties in a Series of Cobalt(II) Complexes and Structural Transformation in Mother Liquor

et al. 2020

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The three Co(II) complexes [Co(bbp) 2 ][Co(NCS) 4 ]•4DMF (1), [Co(bbp)(NCS) 2 (DMF)]•2DMF (2), and [Co(bbp)(NCS) 2 ](3) have been synthesized and characterized by single-crystal X-ray diffraction, magnetic, and various spectroscopic techniques. Complexes 1 and 3 are obtained by the reaction of Co(NCS) 2 with 2,6-bis(1H-benzo[d]imidazol-2yl)pyridine (bbp), and complex 1 undergoes a structural transformation to form complex 2. A single-crystal X-ray study revealed that complex 1 is comprised of two Co(II) centers, a cationic octahedral Co(II) unit and an anionic tetrahedral Co(II) unit, while the Co(II) ion is in a distorted-octahedral environment in 2. Moreover, in complex 3, the Co(II) ion is in a distorted-square-pyramidal geometry. The effect of coordination geometry on the magnetic properties was studied by both static and dynamic magnetic measurements. Direct current (dc) magnetic susceptibility measurements showed that all of the Co(II) ions are in high-spin state in these complexes. Alternating current (ac) magnetic susceptibility measurements indicated that complexes 2 and 3 display slow relaxation of magnetization in an external dc magnetic field, while complex 1 displayed no such property. EPR experiments and theoretical calculations were consistent with the above findings.

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Octahedral–Tetrahedral Systems [Co(dppm^O,O)₃]²⁺[CoX₄]^2– Showing Slow Magnetic Relaxation with Two Relaxation Modes

Cited by 19 publications

References 37 publications

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

Identifying the Imperative Role of Metal–Olefin Interactions in Catalytic C–O Reductive Elimination from Nickel(II)

Effect of Coordination Geometry on Magnetic Properties in a Series of Cobalt(II) Complexes and Structural Transformation in Mother Liquor

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