Oxalate-templated synthesis of di-zinc macrocycles

Beattie, Jeffrey W.; SantaLucia, Daniel J.; White, David S.; Groysman, Stanislav

doi:10.1016/j.ica.2016.02.063

Cited by 13 publications

(7 citation statements)

References 46 publications

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“…In the current study, we have investigated the ability of a dinucleating macrocyclic ligand framework to undergo dramatic geometric changes in response to the varying electronic requirements of the metal centers . This work makes use of 3 PDI 2 , a tert -butylated version of a macrocyclic, pyridyldiimine-based scaffold (Figure ) − that we recently employed for mediating the putative formation of transient dicobalt bridging nitrides .…”

Section: Introductionmentioning

confidence: 99%

Tuning Metal–Metal Interactions through Reversible Ligand Folding in a Series of Dinuclear Iron Complexes

et al. 2019

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A dinucleating macrocyclic ligand with two redox-active, pyridyldiimine components was shown to undergo reversible ligand folding to accommodate various substitution patterns, metal ion spin states, and degrees of Fe–Fe bonding within the cluster. An unfolded-ligand geometry with a rectangular Fe2(μ-Cl)2 core and an Fe–Fe distance of 3.3262(5) Å served as a direct precursor to two different folded-ligand complexes. Chemical reduction in the presence of PPh3 resulted in a diamagnetic, folded ligand complex with an Fe–Fe bonding interaction (d Fe–Fe = 2.7096(17) Å) between two intermediate spin (S Fe = 1) Fe(II) centers. Ligand folding was also induced through anion exchange on the unfolded-ligand species, producing a complex with three PhS– ligands and a temperature-dependent Fe–Fe distance. In this latter example, the weak ligand field of the thiolate ligands led to a product with weakly coupled, high-spin Fe(II) ions (S Fe = 2; J = −50.1 cm–1) that form a bonding interaction in the ground state and a nonbonding interaction in the excited state(s), as determined by SQUID magnetometry and variable temperature crystallography. Finally, both folded-ligand complexes were shown to reform an unfolded-ligand geometry through convergent syntheses of a complex with an Fe–Fe bonded Fe2(μ-SPh)2 core (d Fe–Fe = 2.7320(11) Å). Experimentally validated DFT calculations were used to investigate the electronic structures of all species as a way to understand the origin of Fe–Fe bonding interactions, the extent of ligand reduction, and the nature of the spin systems that result from multiple, weakly interacting spin centers.

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Section: Introductionmentioning

confidence: 99%

Tuning Metal–Metal Interactions through Reversible Ligand Folding in a Series of Dinuclear Iron Complexes

et al. 2019

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“…The metal–metal distances for ( 1 – 3 )M 2 Br 4 are given in Table and range from 5.7600(8) to 6.232(1) Å. Similar distances were observed for macrocyclic bis-PDI complexes in which the PDI units are bridged by m -xylylene linkers, including ([ D ]Cu 2 Im][CF 3 SO 3 ] 3 (Cu–Cu = 5.9181(9) Å), [ E ]Zn 2 Ox][CF 3 SO 3 ] 2 (Zn–Zn = 5.3849(6) Å), ( F )Zn 2 Cl 4 (Zn–Zn = 5.515(1) Å), and ( F )Co 2 Cl 4 (Co–Co = 5.501(1) Å), which are shown in Chart . − In contrast, the Co–Co distance in ( A )Co 2 Cl 4 (R 1 = R 2 = H; 7.731(2) Å) is much longer. While the syn -double-decker complexes ( B )Fe 2 Cl 4 have not been crystallographically characterized, Groysman has reported a similar [( B )Co 2 (CH 3 CN) 4 ][Co(CO) 4 ] 2 complex with a Co–Co distance of 4.628(1) Å .…”

Section: Resultsmentioning

confidence: 57%

Synthesis and Ethylene Reactivity of Dinuclear Iron and Cobalt Complexes Supported by Macrocyclic Bis(pyridine-diimine) Ligands Containing o-Terphenyl Linkers

Reinhart

Jordan

2020

Organometallics

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The synthesis and ethylene reactivity of a new family of dinuclear Co2Br4 and Fe2Br4 complexes supported by binucleating macrocyclic bis(pyridine-diimine) (PDI) ligands that contain 4,4″-R2-3,3″-o-terphenyl linkers (1, R = H; 2, R = Me; 3, R = iPr) are described. In the solid state, (1–3)M2Br4 (M = Zn, Fe, Co) adopt C s -skew-syn structures in which the (PDI)M planes are skewed 49–82° relative to each other and both middle rings of the o-terphenyl bridges are on the same side of the molecule. The metal–metal distances range between 5.7600(8) and 6.232(1) Å. In solution, (1)M2Br4 (M = Zn, Co, Fe) undergo a fluxional process that permutes the two inequivalent (PDI)M units, while (2)M2Br4 and (3)M2Br4 are static and adopt C s -symmetric structures similar to those observed in the solid state. Activation of (2)Fe2Br4 and (3)Fe2Br4 with MMAO-12 or triisobutylaluminum (TIBA) in the presence of ethylene generates catalysts that produce solid polyethylene (M w = 4500–280000 Da), which contrasts with the reported production of α-olefins by analogous mononuclear (PDI)FeCl2 catalysts. (3)Fe2Br4/TIBA and (3)Fe2Br4/MMAO-12 produce polyethylenes with broad molecular weight distributions (MWDs) due to chain transfer to Al. (3)Co2Br4/1000 TIBA and (3)Co2Br4/1000 MMAO-12 also produce polyethylenes with broad MWDs. However, in these cases chain transfer to Al is not operative and the broad MWDs result from multisite behavior.

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“…Two early examples of bis-PDI complexes of this type, [( A )M 2 Im][CF 3 SO 3 ] 3 (M = Cu or Ni), were prepared by Burrows as models for the Ni 2 active site in urease. − These complexes were synthesized by reacting M(OTf) 2 and imidazole (ImH) to form a putative [M–Im–M] 3+ complex, which was then added to a solution of 2,6-diacetylpyridine and m -xylylenediamine. More recently, Groysman showed that an analogous Zn complex, [( A )Zn 2 Ox][CF 3 SO 3 ] 2 (Ox = oxalate), is formed using in situ -generated [Zn 2 Ox] 2+ as the binucleating template . The [Zn 2 Ox] 2+ template also directs the condensation of 2,6-formylpyridine and p -xylylenediamine to produce [( B )Zn 2 Ox][CF 3 SO 3 ] 2 .…”

Section: Introductionmentioning

confidence: 99%

“…More recently, Groysman showed that an analogous Zn complex, [(A)Zn 2 Ox][CF 3 SO 3 ] 2 (Ox = oxalate), is formed using in situ-generated [Zn 2 Ox] 2+ as the binucleating template. 49 The [Zn 2 Ox] 2+ template also directs the condensation of 2,6-formylpyridine and p-xylylenediamine to produce [(B)Zn 2 Ox][CF 3 SO 3 ] 2 . It should be emphasized that the binucleating templates are critical for macrocyclization in the synthesis of [(A)M 2 Im][CF 3 SO 3 ] 3 and [(A)Zn 2 Ox]-[CF 3 SO 3 ] 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

Template-Free Synthesis of a Macrocyclic Bis(pyridine-dienamine) Proligand and Metal Complexes of Its Bis(pyridine-diimine) and Bis(pyridine-dienamido) Forms

Reinhart

Jordan

2019

Inorg. Chem.

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We describe the template-free synthesis of the bis(pyridine-dienamine) proligand [4,5-(m-xylylenediamine)NH–C(CH)(9-butyl-octahydroacridine)]2 (2′), a variant of Burrows’s macrocyclic bis(pyridine-diimine) (bis-PDI) ligand [2,6-(m-xylylenediamine)NC(py)]2 (A), using octahydroacridine as the ligand backbone. The octahydroacridine backbone favors macrocyclization by constraining the PDI units in the (s-cis)2 conformation. The template-free synthesis of 2′ enables facile access to a wide array of bis-PDI and bis(pyridine-dienamido) (bis-PDE) metal complexes. Five-coordinate binuclear bis-PDI (2)M2Cl4 complexes {2 = [4,5-(m-xylylenediamine)NC(9-butyl-octahydroacridine)]2; M = Zn, Co, or Fe} and a four-coordinate bis-PDI [(2)Pd2Br2][B(3,5-(CF3)2-Ph)4]2 complex were synthesized and characterized. (2)Zn2Cl4 undergoes macrocyclic ring inversion on the nuclear magnetic resonance (NMR) time scale with a free energy barrier ΔG ⧧ of 15.5(3) kcal/mol at 295 K. In contrast, (2)Fe2Cl4 and (2)Co2Cl4 undergo slow ring inversion on the NMR chemical shift time scale at 295 K. The amine elimination reaction of 2′ with Zr(NMe2)4 yields the bis-PDE complex (2′-4H)Zr2(NMe2)4, which was alkylated with AlMe3 and Al(CH2SiMe3)3 to generate (2′-4H)Zr2Me4 and (2′-4H)Zr2(CH2SiMe3)2(NMe2)2, respectively.

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Oxalate-templated synthesis of di-zinc macrocycles

Cited by 13 publications

References 46 publications

Tuning Metal–Metal Interactions through Reversible Ligand Folding in a Series of Dinuclear Iron Complexes

Tuning Metal–Metal Interactions through Reversible Ligand Folding in a Series of Dinuclear Iron Complexes

Synthesis and Ethylene Reactivity of Dinuclear Iron and Cobalt Complexes Supported by Macrocyclic Bis(pyridine-diimine) Ligands Containing o-Terphenyl Linkers

Template-Free Synthesis of a Macrocyclic Bis(pyridine-dienamine) Proligand and Metal Complexes of Its Bis(pyridine-diimine) and Bis(pyridine-dienamido) Forms

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