Mixed-valence Trinuclear Complexes Research Articles

In Situ Ligand Transformation in the Synthesis of Manganese Complexes: Mono-, Tri- and a Barrel-shaped Tetradeca-nuclear MnII14Aggregate

Three one-pot syntheses leading to four examples of in situ ligand transformations are presented. These in situ reactions involve various transformations of 2-(N'-dicyanomethylene-hydrazino)-benzoic acid (DHB). The resulting ligands enabled the preparation of three new coordination compounds, which were fully characterized by infrared spectroscopy, elemental analysis, and single crystal X-ray diffraction. The complex, [Mn(III)(Lig-I)(CH(3)OH)Cl] (1), was prepared in a one-pot synthesis in which the aryl hydrazone ligand, (Lig-I)(2-), was formed by the amination of DHB resulting from the nucleophilic attack of an amino group of ethylenediamine. The linear, mixed-valence trinuclear complex, (Et(3)NH)(4)[Mn(III)(2)Mn(II)(mu-OH)(2)(Lig-II)(2)(HLig-II)(2)] (2), was synthesized using a preparation involving the in situ reaction of azide and a nitrile of DHB. Larger species can also be prepared using this technique. In a reaction involving two different in situ ligand formations, the cyclocondensation of two DHB molecules and the partial hydrolysis of a nitrile of DHB, the first example of a tetradecanuclear Mn(II) aggregate, (H(3)O)(4)[Mn(II)(14)(mu(6)-CO(3))(mu(3)-OH)(6)(HLig-III)(6)(HLig-IV)(3)(OH(2))(3)] x 92 MeCN (3), was isolated and characterized. Magnetic measurements on 2 indicate the presence of intramolecular and intermolecular antiferromagnetic interactions (J(1)/k(B) = -9.5(1) K, g = 1.95(2), and zJ'/k(B) = -0.37(5) K) while those on 3 suggest the presence of dominating antiferromagnetic interactions.

A new trinuclear mixed-valence Co(II)–Co(III) complex stabilized by a bis(salicylidene) based ligand

The present work deals with a class I mixed valence trinuclear complex [ Co II ( μ -OAc ) 2 ( μ -L ) 2 Co 2 III ( NCS ) 2 ] ( 1) formed by partial aerial oxidation (H 2L = 1,7-bis(2-hydroxyphenyl)-2,6-diazahepta-1,6-diene). The terminal Co IIIN 3O 3 centres exhibit a uniform facial arrangement of both N 3 and O 3 donor sets and the Co II centre is coordinated to six oxygen atoms. Variable temperature magnetic susceptibility measurement reveals that the intermediate Co(II) paramagnetic centre undergoes a very weak spin exchange ( θ = −6.39 K, antiferromagnetic) interaction with the two terminal Co(III) diamagnetic centres over the range 300–2 K. A three line EPR spectra at 4 K was characterized with highly anisotropic g tensors and the one line broad spectra at 300 K indicates the strong influence of temperature on the metal spin states, consistent with a high spin Co(II) complex. Two anodic responses appeared at +0.85 (Co 2+ → Co 3+, reversible) and +1.7 V (Co 3+ → Co 4+, irreversible) corresponding to one and two electron transfer oxidation respectively. Another reversible signal attributed to Co 3+ → Co 2+ reduction occurred at −0.5 V, associated with a two electron stoichiometry. Compound 1 reacted with hydrazine to form a square planar orange-red [Co II(L)] species, 2. Inter conversion between 1 and 2 involves electron exchange coupled with proton transfer.

A trinuclear complex containing MnIIMnIIIMnIV, radicals, quinone and chloride ligands potentially relevant to PS II

Reaction of MnCl2 with a non-innocent ligand H3L results in an unprecedented mixed-valence trinuclear complex [MnII MnIII MnIV (L)(L*)2(L(IQ))Cl] whose structural and magnetic properties are described.

A linear trinuclear mixed valence vanadium(v/iv/v) complex: synthesis, characterization, and solution behavior

The reaction between vanadium(III) acetylacetonate and N-hexanoylsalicylhydrazide (H3hshz) yields a linear trinuclear mixed valence vanadium(V/IV/V) complex, V3O3(hshz)2(OEt)2, 1 (where hshz3- is a triply deprotonated trianionic N-hexanoyl salicylichydrazidate), with a pseudo C2 symmetry. A V(IV)O2+ group is at the center of complex 1 and is spanned by two terminal vanadium(V) ions with a square pyramidal geometry bridged via hydrazido ligands. In the crystalline form, the oxo group of the central vanadium(IV) ion is weakly coordinated to one of the terminal square pyramidal vanadium(V) ions of the neighboring trinuclear complex to form a dimeric structure. These dimers are linked via bis mu-alkoxo bridges to form a one-dimensional zigzag chain structure. In chloroform or methylene dichloride, the weak linkages between the trinuclear complexes present in the crystalline form are broken, and only the mixed valence trinuclear complex can be identified. In dimethyl sulfoxide or dimethylformamide, the trinuclear complex partially dissociates, and the unligated ligands remain in equilibrium with the trinuclear complex.

Steric Control of Polynuclear Manganese Complexes by the Use of Tripodal Tetradentate Ligands

Abstract Tripodal tetradentate ligands (H2L1: N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L2: N-(3,5-di-t-butyl-2-hydroxybenzyl)-N-(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L3: N,N-bis(3,5-di-t-butyl-2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L4: N,N-bis(2-hydroxy-3-methoxybenzyl)-N′,N′-dimethylethylenediamine, H2L5: N-(3,5-di-t-butyl-2-hydroxybenzyl)-N-(2-hydroxy-3-methoxybenzyl)-N′,N′-dimethylethylenediamine) made it possible to prepare sterically controlled polynuclear manganese complexes. In the presence of carboxylate ligands, in contrast to the L3 ligand which gave mononuclear MnIII complexes, the other ligands afforded mixed-valence trinuclear complexes with an MnIII–MnII–MnIII arrangement. In methanol, the general formula of the products is [Mn3(L)2(carboxylato)2(OCH3)2]. While preparations in acetonitrile generated [Mn3(L1)2(ba)4] (ba = benzoate(1−)) and [Mn3(L2)2(ba)2(OH)2]. The structure of [Mn3(L1)2(ba)4] was determined by X-ray analysis. The three manganese cores are arranged linearly, and the central and terminal ions are bridged by a phenolate and two carboxylate groups. In the case of the L5 ligand, dinuclear and tetranuclear complexes were also obtained and structurally characterized. In the dinuclear complex, [Mn(L5)(CH3OH)(OCH3)MnCl2], a distorted octahedral MnIII and a five-coordinated MnII site are bridged by a phenolate and an alkoxo oxygen donor. The tetranuclear complex, [Mn4(L5)2(ba)6], including an MnIII–MnII–MnII–MnIII arrangement, is regarded as a carboxylato bridged dimer of a dinuclear unit, [Mn(L5)(ba)2Mn]+. Because the bulkiness of the L5 ligand lies between the L2 and L3 ligands, the dinuclear unit is favorable. Variable-temperature magnetic susceptibility measurements showed the ferromagnetic spin-exchange coupling for [Mn(L5)(CH3OH)(OCH3)MnCl2] and the antiferromagnetic one for [Mn3(L1)2(ba)4]. The phenolato and alkoxo bridges give rise to the ferromagnetic exchange interactions between MnIIIand MnII ions. On the other hand, the antiferromagnetic interactions stem from carboxylato bridges.

Mononuclear and Mixed-Valence Trinuclear Manganese Complexes Containing Tripodal Tetradentate Ligands. Phenolato, Carboxylato, and Alkoxo Bridges

Abstract Manganese complexes containing tripodal tetradentate ligands with an N2O2 donor set (H2L1: N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L2: N-(3,5-di-t-butyl-2-hydroxybenzyl)-N-(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L3: N,N-bis(3,5-di-t-butyl-2-hydroxybenzyl)-N′,N′-dimethylethylenediamine) have been prepared. The mononuclear and trinuclear complexes with the additional carboxylate ligand were isolated. The steric effect of the 3-positioned t-butyl groups on the aromatic rings of the tripodal ligand controls the type of the complex structure. The L3 ligand gave a mononuclear complex, [Mn(L3)(mcba)(CH3OH)], where mcba is a m-chlorobenzoate anion; the structure has been determined by X-ray analysis. The trinuclear complexes are formulated as [Mn3(Ln)2(carboxylato)2(OCH3)2] (n = 1, 2). For the L4 and L5 ligands (H2L4: N,N-bis(5-methoxy-2-hydroxybenzyl)-N′,N′-dimethylethylenediamine, H2L5: N,N-bis(5-chloro-2-hydroxybenzyl)-N′,N′-dimethylethylenediamine), trinuclear complexes were also obtained. Three trinuclear complexes were also structurally characterized by X-ray analysis. The three manganese cores are arranged linearly, and the structural parameters indicate that the oxidation states are MnIII–MnII–MnIII. The MnIII and MnII cores are bridged by phenolate, carboxylate, and alkoxide groups, and the manganese cores are separated in the range of 3.14 and 3.17 Å. The variable-temperature magnetic susceptibility measurements of the mixed-valence trinuclear complexes revealed that the spin exchange coupling constants (J) between MnIII and MnII ions range from −0.25 to 1.9 cm−1. The exchange interactions are weak, and both antiferromagnetic and ferromagnetic interactions were observed.

Investigation on the Electron-transfer Interaction of the Two Ferrocene Moieties Bridged by Ni2+ or Cu2+ and Its Mixed-valence Complexes

Abstract Investigation of the new mixed-valence trinuclear complexes of FcMFc (M = Ni, Cu) indicates that intramolecular long-range charge transfer for FcNiFc complex processes in timescale 1.6•106 s−1 through a long bridge including a coordinated bond at room temperature.

Synthesis, Characterization, and Crystal Structure of a Vanadium(V)-Vanadium(IV)-Vanadium(V) Mixed-Valence Trinuclear Complex with a Tridentate Quinato Ligand, (NH4)2{[VV(O)2]2[VIV(O)](.mu.-(-)-quinato(3-))2}.cntdot.H2O

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis, Characterization, and Crystal Structure of a Vanadium(V)-Vanadium(IV)-Vanadium(V) Mixed-Valence Trinuclear Complex with a Tridentate Quinato Ligand, (NH4)2{[VV(O)2]2[VIV(O)](.mu.-(-)-quinato(3-))2}.cntdot.H2ORachel Codd, Trevor W. Hambley, and Peter A. LayCite this: Inorg. Chem. 1995, 34, 4, 877–882Publication Date (Print):February 1, 1995Publication History Published online1 May 2002Published inissue 1 February 1995https://doi.org/10.1021/ic00108a019RIGHTS & PERMISSIONSArticle Views224Altmetric-Citations46LEARN 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 (803 KB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

η3-Allyl rhodium complexes with azolate ligands. Crystal structures of the trinuclear 1,2,4-triazolate (tz) complexes [Rh3(µ-tz)3(η3-C3H5)6] and [Rh3(µ3-tz)(µ-Cl)Cl(η3-C3H5)2(CO)4]·0.5C2H4Cl2

The η3-allyl rhodium compound [Rh(acac)(η3-C3H5)2](acac = acetylacetonate) reacts with azole ligands to give the new azolate complexes [Rh3(µ-az)3(η3-C3H5)6][az = tetrazolate (ttz)(1), 1,2,4-triazolate (tz)(2), benzotriazolate (btz)(3), or imidazolate (im)(4)]. A single-crystal X-ray diffraction study on complex (2) has established that its structure consists of discrete trinuclear complexes in which each rhodium atom is bridged by the 1,2,4-triazolate ligands through the non-adjacent nitrogen atoms to form a multiatomic ring. Complexes (2) and (1) react with [Rh2(µ-Cl)2(CO)4] to give the mixed-valence trinuclear complexes [Rh3(µ3-az)(µ-Cl)Cl(η3-C3H5)2(CO)4][az = tz (10) or ttz (11)]. The crystal structure of complex (10) has confirmed the existence of trinuclear molecules in which a chlorine atom and a triazolate bridge Rh(CO)2 and Rh(η3-C3H5)2 moieties; in addition the remaining nitrogen atom of the triazolate ligand completes the square-planar co-ordination of a RhCl(CO)2 unit. In the crystal, there is an intermolecular Rh–Rh distance of 3.393(1)A. Complex (2) reacts with [Rh2(µ-Cl)2(η3-C3H5)4] to give the trinuclear complex [Rh3(µ3-tz)(µ-Cl)Cl(η3-C3H5)6]. Heterobridged binuclear pyrazolate (pz) complexes of formula [Rh2(µ-pz)(µ-X)(η3-C3H5)4](X = Cl, OH, or N3) have also been prepared.