Syntheses and magnetic properties of hexanuclear [Cp2Mn3(L1)4]2and octanuclear [Mn8(L2)12(μ4-O)2] (L1= 2-HNC5H5N, L2= 2-NH-3-Br-5-MeC5H3N, Cp = C5H5)

Alvarez, Carmen Soria; Bond, Andrew D.; Cave, Dale; Mosquera, Marta E. G.; Harron, Eilis A.; Layfield, Richard A.; McPartlin, Mary; Rawson, Jeremy M.; Wood, Paul T.; Wright, Dominic S.

doi:10.1039/b209496g

“…Consistent with previously reported polynuclear Mn II complexes, 16,27 complexes 1–3 do not feature close Mn–Mn interactions, suggesting an increased bonding interaction within the iron and cobalt analogues. 28 Further, within the trinuclear manganese complexes, the M–M separation is largely unaffected by changing the peripheral ligand anilide substituent from H to Ph.…”

Section: Discussionsupporting

confidence: 91%

“…Modeling the data accordingly provides exchange coupling constants of J 1 = −35(1) and J 2 = −27(1) cm −1 ( g = 2.00(2)) for 1 , J = − 49(2) and J 2 = −39(1) cm −1 ( g = 1.99(3)) for 2 , and J = −29.5(6) and J 2 = –17.5(3) cm −1 ( g = 2.00(3)) for 3 . These values are considerably larger than those reported for related trigonal carboxylate- and amido-bridged Mn II clusters, which exhibit J = −0.59 to −2.36 cm −1 , 21 and J = −7.0 to −11.0 cm −1 , 16f respectively. Considering all trigonal Mn 3 clusters, the magnitude of antiferromagnetic exchange ( J 1 , J 2 ) track somewhat linearly with the Mn–N–Mn bond angle (see Figure S9), wherein the larger angle corresponds to weaker coupling between the metal centers.…”

Section: B Resultscontrasting

confidence: 63%

“…16f Moreover, closer inspection of the Mn–Mn separation in 1 reveals an asymmetry consistent with this formulation, which features two short and one long Mn–Mn distances (Mn1–Mn2 2.8229(4) Å, Mn1–Mn3 2.8155(4) Å, with Mn2–Mn3 2.9267(5) Å). Modeling the data accordingly provides exchange coupling constants of J 1 = −35(1) and J 2 = −27(1) cm −1 ( g = 2.00(2)) for 1 , J = − 49(2) and J 2 = −39(1) cm −1 ( g = 1.99(3)) for 2 , and J = −29.5(6) and J 2 = –17.5(3) cm −1 ( g = 2.00(3)) for 3 .…”

Section: B Resultssupporting

confidence: 60%

“…The range of Mn–Mn separations found in compounds 1–3 are similar to previously reported polynuclear Mn II clusters. 16,17 …”

Section: B Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Trigonal Mn₃ and Co₃ Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Fout

¹

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Xiao

²

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Zhao

³

et al. 2012

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Transamination of divalent transition metal starting materials (M2(N(SiMe3)2)4, M = Mn, Co) with hexadentate ligand platforms RLH6 (RLH6 = MeC(CH2NPh-o-NR)3 where R = H, Ph, Mes (Mes = Mesityl)) or H,CyLH6 = 1,3,5-C6H9(NHPh-o-NH2)3 with added pyridine or tertiary phosphine co-ligands afforded trinuclear complexes of the type (RL)Mn3(py)3 and (RL)Co3(PMe2R’)3 (R’ = Me, Ph). While the sterically less encumbered ligand varieties, HL or PhL, give rise to local square-pyramidal geometries at each of the bound metal atoms, with four anilides forming an equatorial plane and an exogenous pyridine or phosphine in the apical site, the mesityl-substituted ligand (MesL) engenders local tetrahedral coordination. Both the neutral Mn3 and Co3 clusters feature S = 1/2 ground states, as determined by dc magnetometry, 1H NMR spectroscopy, and low-temperature EPR spectroscopy. Within the Mn3 clusters, the long internuclear Mn–Mn separations suggest minimal direct metal-metal orbital overlap. Accordingly, fits to variable-temperature magnetic susceptibility data reveal the presence of weak antiferromagnetic superexchange interactions through the bridging anilide ligands with exchange couplings ranging from J = −16.8 to −42 cm−1. Conversely, the short Co–Co interatomic distances suggest a significant degree of direct metal-metal orbital overlap, akin to the related Fe3 clusters. With the Co3 series, the S = 1/2 ground state can be attributed to population of a single molecular orbital manifold that arises from mixing of the metal- and o-phenylenediamide (OPDA) ligand-based frontier orbitals. Chemical oxidation of the neutral Co3 clusters affords diamagnetic cationic clusters of the type [(RL)Co3(PMe2R)3]+. DFT calculations on the neutral (S = ½) and cationic (S = 0) Co3 clusters reveal that oxidation occurs at an oribital with contributions from both the Co3 core and OPDA subunits. The predicted bond elongations within the ligand OPDA units are corroborated by the ligand bond perturbations observed by X-ray crystallography.

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Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

García‐Álvarez

¹

,

Kennedy

²

,

Klett

³

et al. 2007

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A keystone methodology in synthetic chemistry, metalation (metal-hydrogen exchange) reactions of aromatic compounds are usually the domain of highly reactive polar organometallics such as alkyllithium compounds, LICKOR (alkyllithium compounds cocomplexed with potassium tertbutoxide) superbases, or lithium amides.[1] Strictly these reactions are lithiations (or potassiations) as the incoming lithium atom (or potassium atom) takes the place of the outgoing hydrogen atom. The lower-polarity metals magnesium, zinc, and aluminum generally form slow-reacting metalating agents which are ineffective towards aromatic compounds. Therefore, to attach these less reactive metals directly to an aromatic scaffold, the lithiated aromatic compound must be synthesized beforehand and then an additional metathetical reaction often involving a metal halide (for example, RMgX, ZnX 2 , or R 2 AlX) has to be carried out. The presence of the ionic halide often limits the range of solvents available for such reactions with hydrocarbons and arenes, which are generally ruled out in favor of polar substitutes (commonly ether or THF). Recently, however, it has been shown that pairing lithium (or another alkali metal) with one of these inferior multivalent metals in the same organometallic molecule (an "-ate" formulation), can generate "synergic", mixed-metal reagents capable of directly magnesiating, [2,3] zincating, [3] or aluminating [4] aromatic substrates, thus circumventing the need for a subsequent metathesis. In addition to this new inorganic (metal) perspective, these synergic reagents can open up new organic horizons by promoting unusual regioselective deprotonations (for example, meta-orientated in the cases of toluene [5] and N,Ndimethylaniline [6] ) or special polydeprotonations (for example, 2,6-twofold in the case of naphthalene [7] and 1,1',3,3'-fourfold in the cases of ferrocene and its Group 8 homologues [8] ). This Communication addresses the question, "could this developing idea of alkali-metal-mediated metalation, established with the main-group/pseudo-main-group s-electron metals Mg, Zn, and Al, be extended to other categories of metal?" Incorporating a transition metal as the divalent partner would be especially attractive, for it would potentially open up a treasure chest of new chemistry given the much greater breadth of properties (for example, redox, magnetic, catalytic) available to a bona fide d-block element. Herein, we report our success in this endeavor with the Group 7 metal manganese.Our first task was to design a suitable mixed alkali-metal/ manganese(II) reagent in the mould of, for example, [(tmeda)Na(tmp)(tBu)Zn(tBu)](tmeda = N,N,N',N'-tetramethylethylenediamine, tmp = 2,2,6,6-tetramethylpiperidide), [9] which has proved extremely adept at accomplishing alkali-metal-mediated zincation (AMMZ) of aromatic substrates. Conscious of the general instability of organomanganese(II) compounds, we selected the known [10] thermally stable (no b-H decomposition pathway is possible) neutral dialkyl complex [(MnR 2 ) 1 ...

show abstract

Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

García‐Álvarez

¹

,

Kennedy

²

,

Klett

³

et al. 2007

View full text Add to dashboard Cite

A keystone methodology in synthetic chemistry, metalation (metal-hydrogen exchange) reactions of aromatic compounds are usually the domain of highly reactive polar organometallics such as alkyllithium compounds, LICKOR (alkyllithium compounds cocomplexed with potassium tertbutoxide) superbases, or lithium amides.[1] Strictly these reactions are lithiations (or potassiations) as the incoming lithium atom (or potassium atom) takes the place of the outgoing hydrogen atom. The lower-polarity metals magnesium, zinc, and aluminum generally form slow-reacting metalating agents which are ineffective towards aromatic compounds. Therefore, to attach these less reactive metals directly to an aromatic scaffold, the lithiated aromatic compound must be synthesized beforehand and then an additional metathetical reaction often involving a metal halide (for example, RMgX, ZnX 2 , or R 2 AlX) has to be carried out. The presence of the ionic halide often limits the range of solvents available for such reactions with hydrocarbons and arenes, which are generally ruled out in favor of polar substitutes (commonly ether or THF). Recently, however, it has been shown that pairing lithium (or another alkali metal) with one of these inferior multivalent metals in the same organometallic molecule (an "-ate" formulation), can generate "synergic", mixed-metal reagents capable of directly magnesiating, [2,3] zincating, [3] or aluminating [4] aromatic substrates, thus circumventing the need for a subsequent metathesis. In addition to this new inorganic (metal) perspective, these synergic reagents can open up new organic horizons by promoting unusual regioselective deprotonations (for example, meta-orientated in the cases of toluene [5] and N,Ndimethylaniline [6] ) or special polydeprotonations (for example, 2,6-twofold in the case of naphthalene [7] and 1,1',3,3'-fourfold in the cases of ferrocene and its Group 8 homologues [8] ). This Communication addresses the question, "could this developing idea of alkali-metal-mediated metalation, established with the main-group/pseudo-main-group s-electron metals Mg, Zn, and Al, be extended to other categories of metal?" Incorporating a transition metal as the divalent partner would be especially attractive, for it would potentially open up a treasure chest of new chemistry given the much greater breadth of properties (for example, redox, magnetic, catalytic) available to a bona fide d-block element. Herein, we report our success in this endeavor with the Group 7 metal manganese.Our first task was to design a suitable mixed alkali-metal/ manganese(II) reagent in the mould of, for example, [(tmeda)Na(tmp)(tBu)Zn(tBu)](tmeda = N,N,N',N'-tetramethylethylenediamine, tmp = 2,2,6,6-tetramethylpiperidide), [9] which has proved extremely adept at accomplishing alkali-metal-mediated zincation (AMMZ) of aromatic substrates. Conscious of the general instability of organomanganese(II) compounds, we selected the known [10] thermally stable (no b-H decomposition pathway is possible) neutral dialkyl complex [(MnR 2 ) 1 ...

show abstract

Syntheses and magnetic properties of hexanuclear [Cp₂Mn₃(L₁)₄]₂and octanuclear [Mn₈(L₂)₁₂(μ₄-O)₂] (L₁= 2-HNC₅H₅N, L₂= 2-NH-3-Br-5-MeC₅H₃N, Cp = C₅H₅)

Cited by 33 publications

References 20 publications

Trigonal Mn₃ and Co₃ Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Trigonal Mn₃ and Co₃ Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

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Syntheses and magnetic properties of hexanuclear [Cp2Mn3(L1)4]2and octanuclear [Mn8(L2)12(μ4-O)2] (L1= 2-HNC5H5N, L2= 2-NH-3-Br-5-MeC5H3N, Cp = C5H5)

Cited by 33 publications

References 20 publications

Trigonal Mn3 and Co3 Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Trigonal Mn3 and Co3 Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

Alkali‐Metal‐Mediated Manganation: A Method for Directly Attaching Manganese(II) Centers to Aromatic Frameworks

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Syntheses and magnetic properties of hexanuclear [Cp₂Mn₃(L₁)₄]₂and octanuclear [Mn₈(L₂)₁₂(μ₄-O)₂] (L₁= 2-HNC₅H₅N, L₂= 2-NH-3-Br-5-MeC₅H₃N, Cp = C₅H₅)

Trigonal Mn₃ and Co₃ Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure

Trigonal Mn₃ and Co₃ Clusters Supported by Weak-Field Ligands: A Structural, Spectroscopic, Magnetic, and Computational Investigation into the Correlation of Molecular and Electronic Structure