Bridging Acetate Ligands Research Articles

Dinuclear zinc(II) acetate complexes derived from N,N',S-tridentate Schiff bases: synthesis, structural study and Hirshfeld surface analysis.

Three dinuclear zinc(II) acetate complexes of the general formula [Zn{Ln}(AcO)]2, namely, di-μ-acetato-κ4O:O'-bis[({2-[(pyridin-2-ylmethylidene)amino]phenyl}sulfanido-κ3N,N',S)zinc(II)], [Zn2(C12H9N2S)2(C2H3O2)2] (n= 1), 4, μ-acetato-1:2κ2O:O'-acetato-2κO-[μ-(2-{[1-(pyridin-2-yl)ethylidene]amino}phenyl)sulfanido-1κS:2κ3N,N',S][(2-{[1-(pyridin-2-yl)ethylidene]amino}phenyl)sulfanido-1κ3N,N',S]dizinc(II), [Zn2(C13H11N2S)2(C2H3O2)2] (n= 2), 5, and μ-acetato-1:2κ2O:O'-acetato-2κO-[μ-(2-{[phenyl(pyridin-2-yl)methylidene]amino}phenyl)sulfanido-1κS:2κ3N,N',S][(2-{[phenyl(pyridin-2-yl)methylidene]amino}phenyl)sulfanido-1κ3N,N',S]dizinc(II)-bis(2-aminophenyl) disulfide (2/1), [Zn2(C18H13N2S)2(C2H3O2)2]·0.5C12H12N2S2 (n= 3), 6·0.5(2-APS)2, were obtained from the reaction of 2-R-(pyridin-2-yl)benzothiazoline precursors (R= H, 1; R= Me, 2; R= Ph, 3) with zinc acetate dihydrate in a 1:1 ratio. All the complexes crystallized as dinuclear species and complex 6 cocrystallized with one molecule of bis(2-aminophenyl) disulfide (2-APS)2. The anionic Schiff base ligands {Ln}- displayed a κ2N,κS-tridentate coordination mode with the formation of two five-membered chelate rings. In 4, 5 and 6·0.5(2-APS)2, both ZnII ions are pentacoordinated and the coordination sphere of 4 was different with respect to those in 5 and 6·0.5(2-APS)2. For 4, the X-ray diffraction study showed a dinuclear complex containing two bridging acetate ligands linked to both ZnII ions. For 5 and 6·0.5(2-APS)2, the dinuclear complexes displayed one bridging acetate ligand linked to both ZnII ions, where the first ZnII ion includes a dative bond with one S atom from an adjacent anionic Schiff base {Ln}-, while the second ZnII ion is coordinated to one terminal acetate ligand. In each dinuclear complex, the geometry is the same for both ZnII metal centres. The local geometry of the ZnII cation in 4 is halfway between trigonal bipyramidal and square pyramidal local geometries; in 5 and 6, the local geometries are described as distorted square pyramidal. Hirshfeld surface analysis of 5 and 6 showed the predominance of H...H interactions, as well as the contribution of C-H...C, C-H...O and C-H...S noncovalent interactions to the cohesion of the crystalline network of the ZnII complexes.

Synthesis and crystal structures of rhodium acetate paddle‐wheel complexes with anchor group‐functionalised and hydrogen bond‐supported axial ligands

AbstractWe report the synthesis and X‐ray structures of four Rh2(OAc)4(LAx)2 (OAc=acetate, CH3COO−) paddle‐wheel complexes (C1−C4) with methylthio‐modified axial ligands LAx derived from benzamidine (L1), anilinopyrimidine (L2) or isothiourea (L3, L4) that are capable of forming N−H⋅⋅⋅O hydrogen bonds to the equatorially bridging acetate ligands. This was done with the aim to suppress dissociation of the axial ligands and to make the complexes amenable to single‐molecule conductance measurements in a scanning tunneling microscope break‐junction (STM‐BJ) setup. The characteristic spectroscopic features (NMR, IR, vis), crystal structures, the hydrogen‐bonding motifs and a DFT‐based screening of their frontier molecular orbitals are presented. Our calculations suggest that hydrogen‐bonding stabilises axial ligand binding by 15 kJ/mol to 30 kJ/mol and that the HOMO of the rhodium paddle‐wheels is closer to the Au work function than the LUMO, so that the rhodium paddle‐wheels are expected to constitute hole conductors.

A di‑iron(III) μ-oxido complex as catalyst precursor in the oxidation of alkanes and alkenes

The oxido-bridged diiron(III) complex [Fe2(μ-O)(μ-OAc)(DPEAMP)2](OCH3) (1), based on a new unsymmetrical ligand with an N4O donor set, viz. [2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-((ethylamino)methyl)-4-methylphenol (HDPEAMP)], has been prepared and characterized by spectroscopic methods and X-ray crystallography. The crystal structure of the complex reveals that each Fe(III) ion is coordinated by three nitrogen and three oxygen donors, two of which are the bridging oxido and acetate ligands. Employing H2O2 as a terminal oxidant, 1 is capable of oxidizing a number of alkanes and alkenes with high activity. The catalytic oxidation of 1,2-dimethylcyclohexane results in excellent retention of configuration. Monitoring of the reaction of 1 with H2O2 and acetic acid in the absence of substrate, using low-temperature UV–Vis spectroscopy, suggests the in situ formation of a transient Fe(III)2-peroxido species. While the selectivity and nature of oxidation products implicate a high-valent iron-oxido complex as a key intermediate, the low alcohol/ketone ratios suggest a simultaneous radical-based process.

Synthesis of Homo- and Heteronuclear Rare-Earth Metal Complexes Stabilized by Ethanolamine-Bridged Bis(phenolato) Ligands and Their Application in Catalyzing Reactions of CO2 and Epoxides.

A series of homonuclear rare-earth (RE) metal complexes (1Y, 2Yb, 3Nd, and 4La) and heteronuclear RE-Zn complexes (1Y-Zn, 3Nd-Zn, and 5Sm-Zn) stabilized by ethanolamine-bridged bis(phenolato) ligands was prepared and structurally characterized. Heteronuclear complexes are assembled through bridging acetate ligands, and their formation and characterization add to the diversity of 3d-4f complexes. Their activities in mediating reactions of CO2 and epoxides were evaluated and compared. Heteronuclear RE-Zn complexes found application in the copolymerization of cyclohexene oxide and CO2, giving rise to acetate-group-capped copolymers. Homonuclear complexes showed good activity in catalyzing the cycloaddition of variously monosubstituted epoxides and CO2 (1 bar), generating cyclic carbonates in 65-96% yield. For sterically hindered disubstituted epoxides, good yields of 60-91% were achieved in the presence of 10 bar CO2.

Mixed ligand complexes of cadmium(II) and copper(II) dithiocarbazate: Synthesis, spectral characterization, X-ray crystal structure

Three dithiocarbazate complexes, CdL2 (1), Cu2L2(OAc)2 (2) and [CuLCl]n (3), are synthesized using S-allyl-3-[(2-pyridyl-methylene)]dithiocarbazate (HL) as tridentate ligand. All compounds are characterized by elemental analysis, molar conductance, FT-IR and UV–Vis spectroscopy, mass spectrometry and single crystal X-ray diffraction. In all the complexes, the ligand (L−) coordinates to the metal centers through the pyridine nitrogen, the azomethine nitrogen and the thiolate sulfur atoms. In compound 1, two ligand units encompass the cadmium(II) ion in bischelate distorted octahedral fashion. In the copper binuclear compound (2), each metal atom is coordinated to one L− ligand unit and the two copper atoms are held by two bridging acetate ligands. In the coordination polymer 3, copper has a distorted square pyramidal geometry in which L− holds three coordination positions and two chloride ligands complete the five-coordinated arrangement, so that each chlorine atom links two adjacent Cu centers. Molecular geometries, vibrational frequencies and optimized structure energies are compared using the density functional method (B3LYP) with 6–311++G(d,p) basis set. Electronic absorption spectra of compounds are predicted with TD-DFT studies and compared with experimental ones. Natural bond orbital analysis (NBO) is performed for HOMO-LUMO, charge delocalization, intramolecular hydrogen bonding and orbital contributions.

Synthesis and Structural Characterization of Trimanganese‐Containing Polyoxovanadates with Carboxylate Ligands

A trimanganese core containing polyoxovanadate {Et4N}5[Mn3(OAc)(H2O)V10O30] (I; OAc = acetate) was synthesized by the reaction of {Et4N}[VO3] with Mn(OAc)2 (0.3 equiv.) in acetonitrile. The trimanganese core possesses a bridging acetate ligand. To demonstrate the ligand‐exchange properties of I, its reaction with benzoic acid (1 equiv.) was conducted and {Et4N}5[Mn3(OBz)(H2O)V10O30] (II; OBz = benzoate) was formed quantitatively. By using a dicarboxylate, the inorganic–organic–inorganic hybrid {Et4N}10[{Mn3(H2O)V10O30}2{OOC(CH2)nCOO}] [n = 3 (III) and n = 4 (IV)] compounds were synthesized. To compensate the negative–negative repulsion between the anionic groups with a 5– charge, tetraethylammonium cations are sandwiched between the anionic groups in the crystallographic packing. Despite the differences in the bridging carbon numbers, both complexes have the same orientation in the crystal state except for the conformation of the alkyl chains, which suggests the presence of a unique interaction with an anion–cation–anion motif to form V‐shaped dimer configurations.

Two cadmium coordination polymers with bridging acetate and phenyl-enedi-amine ligands that exhibit two-dimensional layered structures.

Poly[tetra-μ2-acetato-κ8O:O'-bis-(μ2-benzene-1,2-di-amine-κ2N:N')dicadmium], [Cd2(CH3COO)4(C6H8N2)2] n , (I), and poly[[(μ2-acetato-κ2O:O')(acetato-κ2O,O')(μ2-benzene-1,3-di-amine-κ2N:N')cadmium] hemihydrate], {[Cd(CH3COO)2(C6H8N2)]·0.5H2O} n , (II), have two-dimensional polymeric structures in which monomeric units are joined by bridging acetate and benzenedi-amine ligands. Each of the CdII ions has an O4N2 coordination environment. The coordination geometries of the symmetry-independent CdII ions are distorted octa-hedral and distorted trigonal anti-prismatic in (I) and distorted anti-prismatic in (II). Both compounds exhibit an intra-layer hydrogen-bonding network. In addition, the water of hydration in (II) is involved in inter-layer hydrogen bonding.

Water inclusion mediated structural diversity and the role of H-bonds in molecular assemblies of manganese(III) bicompartmental Schiff-base complexes

Six new manganese(III) derivatives using the ligand H2MeOsalen: N,N′-ethylenebis(3-methoxysalicylaldiimine), have been synthesized and structurally characterized. In all cases the manganese ion is six-coordinated and occupies the internal cavity of the bicompartmental salen ligand. The manganese ion completes its coordination environment with one axial water molecule and one additional ligand, either water, ethanol or one acetate anion. The molecular unit is dimerized by the insertion of the coordinated water molecule into the external MeOsalen cavity of one neighbouring complex. This supramolecular dimer constitutes the structural basis for these compounds, the differences arising from the intermolecular hydrogen bonds involving the counter anions and crystallization solvent molecules. In this way, examples of pseudopolymorphism, cocrystallization and water/anion tapes held by the interaction with the complex dimers are described. The compound [{Mn(MeOsalen)K(H2O)0.5}2(μ-OOCMe)](PF6)3·HOCH2CH2OH is a heterometallic Mn/K derivative where the potassium ion occupies the external cavity, while the coordination of the manganese ion is completed by bridging acetate and ethyleneglycol ligands. The formation of ethyleneglycol is attributed to a stoichiometric oxidation of the ethanol solvent, attributed to the presence of the potassium ion in the complex.

Structurally Diverse Diazafluorene-Ligated Palladium(II) Complexes and Their Implications for Aerobic Oxidation Reactions

4,5-Diazafluoren-9-one (DAF) has been identified as a highly effective ligand in a number of Pd-catalyzed oxidation reactions, but the mechanistic basis for its utility has not been elucidated. Here, we present the complex coordination chemistry of DAF and palladium(II) carboxylate salts. Multiple complexes among an equilibrating mixture of species have been characterized by (1)H and (15)N NMR spectroscopy and X-ray crystallography. These complexes include monomeric and dimeric Pd(II) species, with monodentate (κ(1)), bidentate (κ(2)), and bridging (μ:κ(1):κ(1)) DAF coordination modes. Titration studies of DAF and Pd(OAc)2 reveal the formation of two dimeric DAF/Pd(OAc)2 complexes at low [DAF] and four monomeric species at higher [DAF]. The dimeric complexes feature two bridging acetate ligands together with either a bridging or nonbridging (κ(1)) DAF ligand coordinated to each Pd(II) center. The monomeric structures consist of three isomeric Pd(κ(1)-DAF)2(OAc)2 complexes, together with Pd(κ(2)-DAF)(OAc)2 in which the DAF exhibits a traditional bidentate coordination mode. Replacing DAF with the structurally related, but more-electron-rich derivative 9,9-dimethyl-4,5-diazafluorene (Me2DAF) simplifies the equilibrium mixture to two complexes: a dimeric species in which the Me2DAF bridges the two Pd centers and a monomeric species with a traditional κ(2)-Me2DAF coordination mode. The use of DAF in combination with other carboxylate ligands (CF3CO2(-) or tBuCO2(-)) also results in a simplified collection of equilibrating Pd(II)-DAF complexes. Collectively, the results highlight the ability of DAF to equilibrate rapidly among multiple coordination modes, and provide valuable insights into the utility of DAF as a ligand in Pd-catalyzed oxidation reactions.

Crystal structure of a tetranuclear Cu(II) complex with an O,N,N'-donor Schiff base ligand: hexa-μ2-acetato-bis-(2-{[(2,2,6,6-tetra-methyl-piperidin-4-yl)imino]-meth-yl}phenolato-κ(3) O,N,N')tetra-copper(II).

The title compound, [Cu4(CH3COO)6(C16H23N2O)2], lies across a twofold rotation axis. The asymmetric unit contains two independent Cu(II) ions. The symmetry-unique terminal Cu(II) ion is O,N,N'-coordinated by a 2-{[(2,2,6,6-tetra-methyl-piperidin-4-yl)imino]-meth-yl}phenolate ligand and an O atom from an acetate group in a slightly distorted square-planar coordination environment. The symmetry-unique central Cu(II) ion is coordinated by a different O atom from the same acetate group and by four bridging acetate ligands, which connect the asymmetric unit into a dimeric complex and form a distorted square-pyramidal coordination environment. Within the complex there are two symmetry-equivalent intra-molecular N-H⋯O hydrogen bonds. In the crystal, weak C-H⋯O hydrogen bonds link the complex mol-ecules, forming a three-dimensional network.

β,β'-Bipyrrole Fusion-Driven cis-Bimetallic Complexation in Isomeric Porphyrin.

An unprecedented cis-bimetallic complex of dinaphthoporphycene (DNP), namely [Pd2(μ-DNP)(μ-OAc)2], is reported. The most striking feature of this complex is that two palladiums coordinate to the macrocycle on the same side and are closely held together (Pd-Pd: 2.67 Å) by two bridging acetate ligands exhibiting significant metal-metal bonding interaction (bond order 0.18 evaluated by NBO analysis). Interestingly, replacing acetate with acetylacetonate (acac) could stabilize an unusual mono-palladium complex of DNP, where Pd coordinates unsymmetrically to two ring Ns above the macrocyclic plane, as well as coordinating with two Os of the acac ligand. Remarkably, the rigid DNP core displays enhanced complexation induced aromaticity (as per NICS and HOMA analysis), despite undergoing severe core deformation during complexation with metal ion(s) as noticed from their solid-state structures.

β,β′‐Bipyrrole Fusion‐Driven cis‐Bimetallic Complexation in Isomeric Porphyrin

AbstractAn unprecedented cis‐bimetallic complex of dinaphthoporphycene (DNP), namely [Pd2(μ‐DNP)(μ‐OAc)2], is reported. The most striking feature of this complex is that two palladiums coordinate to the macrocycle on the same side and are closely held together (PdPd: 2.67 Å) by two bridging acetate ligands exhibiting significant metal–metal bonding interaction (bond order 0.18 evaluated by NBO analysis). Interestingly, replacing acetate with acetylacetonate (acac) could stabilize an unusual mono‐palladium complex of DNP, where Pd coordinates unsymmetrically to two ring Ns above the macrocyclic plane, as well as coordinating with two Os of the acac ligand. Remarkably, the rigid DNP core displays enhanced complexation induced aromaticity (as per NICS and HOMA analysis), despite undergoing severe core deformation during complexation with metal ion(s) as noticed from their solid‐state structures.

Crystal structures of three lead(II) acetate-bridged diaminobenzene coordination polymers

Poly[tris-(acetato-κ(2) O,O')(μ2-acetato-κ(3) O,O':O)tetra-kis-(μ3-acetato-κ(4) O,O':O:O')bis-(benzene-1,2-di-amine-κN)tetra-lead(II)], [Pb4(CH3COO)8(C6H8N2)2] n , (I), poly[(acetato-κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(4-chloro-benzene-1,2-diamine-κN)lead(II)], [Pb(CH3COO)2(C6H7ClN2)] n , (II), and poly[(κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(3,4-di-amino-benzo-nitrile-κN)lead(II)], [Pb(CH3COO)2(C7H7N3)] n , (III), have polymeric structures in which monomeric units are joined by bridging acetate ligands. All of the Pb(II) ions exhibit hemidirected coordination. The repeating unit in (I) is composed of four Pb(II) ions having O6, O6N, O7 and O6N coordination spheres, respectively, where N represents a monodentate benzene-1,2-di-amine ligand and O acetate O atoms. Chains along [010] are joined by bridging acetate ligands to form planes parallel to (10-1). (II) and (III) are isotypic and have one Pb(II) ion in the asymmetric unit that has an O6N coordination sphere. Pb2O2 units result from a symmetry-imposed inversion center. Polymeric chains parallel to [100] exhibit hydrogen bonding between the amine and acetate ligands. In (III), additional hydrogen bonds between cyano groups and non-coordinating amines join the chains by forming R 2 (2)(14) rings.

Di-μ2-acetato-1:2κ2O:O′;2:3κ2O:O′-bis{μ2-4,4′-dichloro-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethanylylidene)]diphenolato}-1:2κ6O,N,N′,O′:O,O′;2:3κ6O,O′:O,N,N′,O′-tricadmium

In the title linear homo-trinuclear complex, [Cd3(C19H18Cl2N2O2)2(C2H3O2)2], the central CdII atom is located on a centre of inversion and has a distorted octa­hedral coordination geometry formed by four O atoms from two bidentate/tetra­dentate Schiff base ligands and two O atoms from two bridging acetate ligands. The coordination geometry of the terminal CdII atom is square-pyramidal with the tetra­dentate part of the ligand in the basal plane and one O atom from an acetate ligand occupying the apical site. The six-membered CdN2C3 ring adopts a chair conformation. The acetate-bridged Cd⋯Cd distance is 3.3071 (2) Å. The crystal structure is stabilized by C—H⋯O hydrogen bonds, which form C(7) chain motifs and give rise to a two-dimensional supra­molecular network structure lying parallel to the ab plane.

Syntheses, Structures, Magnetic Properties, and Density Functional Theory Magneto-Structural Correlations of Bis(μ-phenoxo) and Bis(μ-phenoxo)-μ-acetate/Bis(μ-phenoxo)-bis(μ-acetate) Dinuclear FeIIINiII Compounds

The bis(μ-phenoxo) Fe(III)Ni(II) compound [Fe(III)(N3)2LNi(II)(H2O)(CH3CN)](ClO4) (1) and the bis(μ-phenoxo)-μ-acetate/bis(μ-phenoxo)-bis(μ-acetate) Fe(III)Ni(II) compound {[Fe(III)(OAc)LNi(II)(H2O)(μ-OAc)](0.6)·[Fe(III)LNi(II)(μ-OAc)2](0.4)}(ClO4)·1.1H2O (2) have been synthesized from the Robson type tetraiminodiphenol macrocyclic ligand H2L, which is the [2 + 2] condensation product of 4-methyl-2,6-diformylphenol and 2,2'-dimethyl-1,3-diaminopropane. Single-crystal X-ray structures of both compounds have been determined. The cationic part of the dinuclear compound 2 is a cocrystal of the two species [Fe(III)(OAc)LNi(II)(H2O)(μ-OAc)](+) (2A) and [Fe(III)LNi(II)(μ-OAc)2](+) (2B) with weights of 60% of the former and 40% of the latter. While 2A is a triply bridged bis(μ-phenoxo)-μ-acetate system, 2B is a quadruply bridged bis(μ-phenoxo)-bis(μ-acetate) system. Variable-temperature (2-300 K) magnetic studies reveal antiferromagnetic interaction in 1 and ferromagnetic interaction in 2 with J values of -3.14 and 7.36 cm(-1), respectively (H = -2JS1·S2). Broken-symmetry density functional calculations of exchange interaction have been performed on complexes 1 and 2 and also on previously published related compounds, providing good numerical estimates of J values in comparison to experiments. The electronic origin of the difference in magnetic behavior of 1 and 2 has been well understood from MO analyses and computed overlap integrals of BS empty orbitals. The role of acetate and thus its complementarity/countercomplementarity effect on the magnetic properties of diphenoxo-bridged Fe(III)Ni(II) compounds have been determined on computing J values of model compounds by replacing bridging acetate and nonbridging acetate ligand(s) by water ligands in the model compounds derived from 2A,B. The DFT calculations have also been extended to develop several magneto-structural correlations in these types of complexes, and the correlations focus on the role of Fe-O-Ni bridge angle, average Fe/Ni-O bridge distance, Fe-O-Ni-O dihedral angle, and out-of-plane shift of the phenoxo group.

Cubane-Type CuII4 and MnII2MnIII2 Complexes Based on Pyridoxine: A Versatile Ligand for Metal Assembling

By using Vitamin B6 in its monodeprotonated pyridoxine form (PN-H) [PN = 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine], two tetranuclear compounds of formula [Mn4(PN-H)4(CH3CO2)3Cl2]Cl·2CH3OH·2H2O (1) and [Cu4(PN-H)4Cl2(H2O)2]Cl2 (2) have been synthesized and magneto-structurally characterized. 1 crystallizes in the triclinic system with space group P1 whereas 2 crystallizes in the orthorhombic system with Fdd2 as space group. They exhibit Mn(II)2Mn(III)2 (1) and Cu(II)4 (2) cubane cores containing four monodeprotonated pyridoxine groups simultaneously acting as chelating and bridging ligands (1 and 2), three bridging acetate ligands in the syn-syn conformation (1), and two terminally bound chloride anions (1 and 2) plus two coordinated water molecules (2). The electroneutrality is achieved by the presence of chloride counterions in both compounds. Tri- [Mn(1) and Mn(3)] and divalent [Mn(2) and Mn(4)] manganese centers coexist in 1, all being six-coordinate with distorted Mn(1/3)O6 and Mn(2/4)O5Cl octahedral surroundings, respectively, the equatorial Mn-O bonds being about 0.2 Å shorter at the former ones. The two crystallographically independent copper(II) ions in 2 are five-coordinate in somewhat distorted CuO5 [Cu(1)] and CuO4Cl [Cu(2)] square pyramidal geometries. The values of the intracore metal-metal separation cover the ranges 3.144(1)-3.535(1) (1) and 2.922(6)-3.376(1) Å (2). The magnetic properties of 1 and 2 were investigated in the temperature range 1.9-300 K, and they correspond to an overall antiferromagnetic behavior with susceptibility maxima at 5.0 (1) and 65.0 K (2). The analysis of the magnetic susceptibility data showed the coexistence of intracore antiferro- and ferromagnetic interactions in the two compounds. Their values compare well with those existing in the literature for the parent systems.

Different Metal Aggregation in Copper Acetate Chain Coordination Polymers with Dipyridyl Tethers Bearing Hydrogen Bonding Capable Functional Groups

AbstractHydrothermal synthesis has afforded a pair of divalent copper acetate coordination polymers containing either 4, 4′‐dipyridylamine (dpa) or 4‐pyridylisonicotinamide (4‐pina), both of which hydrogen‐bonding capable central functional groups. X‐ray crystallography revealed that both exhibit a 1D chain dimensionality. Use of the kinked tethering ligand dpa produced [Cu(OAc)2(dpa)]n (1), which possesses a simple chain based on dpa linkage of isolated copper ions. On the other hand, employing the straighter amide ligand 4‐pina generated {[Cu(OAc)2(4‐pina)]·0.5H2O}n (2), which exhibits {Cu2O2} rhomboid dimers formed through bridging acetate ligands. Weak antiferromagnetic coupling [g = 1.984(3), J = –3.2(3) cm–1] was observed within the axial‐equatorial bridged {Cu2O2} dimers in 2, with possible ferrimagnetism due to spin canting below 11 K.

Chelate Structure of a Dirhodium–Amino Acid Complex Identified by Chiroptical and NMR Spectroscopy

AbstractDinuclear rhodium complexes have attracted considerable attention as a result of their chemical and biological reactivity. We report herein the synthesis and structural elucidation by combined spectroscopic methods of a new rhodium complex containing N‐methyl‐D‐phenylalaninate (NMfO–) as a chiral ligand. It has been demonstrated that the structure of the chiral complex formed in water is independent of the ligand/metal molar ratio, the type of solvent, and reaction time, as shown by HPLC and ESI‐MS analyses. The steric structure of the isolated and identified [Rh2(OAc)2(OfMN)2] complex was determined by chiroptical (VCD, ECD) and NMR spectroscopy supported by DFT calculations. By this combined analysis, our studies have shown that the complex formed has two chiral ligands chelated through the O and N atoms of their carboxylate and sec‐amino groups, respectively, in the vicinity of the two bridging acetate ligands.

Unusual stability of reaction intermediates in ortho-metalation reactions of dicyclohexylphenylphosphane with dirhodium(II) tetraacetate

Reaction of dirhodium(II) tetraacetate with 1 molar equivalent of dicyclohexylphenylphosphane afforded the complex [Rh2(μ-O2CCH3)3{μ-(C6H4)PCy2}(CH3COOH)2] (1) in which the phosphane ligand is coordinated to the rhodium atoms in a bridging ortho-metalated mode. As a second product, [Rh2(μ-O2CCH3)3{μ-(C6H4)PCy2}(CH3COOH)(PhPCy2)] (2) was isolated from the same reaction. 2 proved to be unusually stable toward further reaction to a doubly ortho-metalated complex which has been accessible in the reaction of dirhodium(II) tetraacetate with other phosphane ligands. However, doubly ortho-metalated [Rh2(μ-O2CCH3)2{μ-(C6H4)PCy2}2(CH3COOH)2] (4) was isolated in low yield after a prolonged thermal reaction between dirhodium(II) tetraacetate and 2 equivalents of PhPCy2. Exchange of the bridging acetate ligands in 1 and 4 by trifluoroacetate ligands afforded [Rh2(μ-O2CCF3)3{μ-(C6H4)PCy2}(CF3COOH)2] (5) and [Rh2(μ-O2CCF3)2{μ-(C6H4)PCy2}2(CF3COOH)2] (7a). Complex 7a without axial ligands, [Rh2(μ-O2CCF3)2{μ-(C6H4)PCy2}2] (7b) was isolated, as well. The crystal structure of complex 5 was determined showing consequences of the bulky cyclohexyl groups on several structural parameters.

Di-μ2-acetato-1:2κ2O:O′;2:3κ2O:O′-bis{μ2-4,4′-dichloro-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethanylylidene)]diphenolato}-1:2κ6O,N,N′,O′:O,O′;2:3κ6O,O′:O,N,N′,O′-tricopper(II)

The title compound, [Cu3(C19H18Cl2N2O2)2(CH3CO2)2], is a linear homo-trinuclear CuII complex. The central CuII atom is located on a centre of inversion and has a distorted octa­hedral coordination environment formed by six O atoms from two tetra­dentate Schiff base ligands and two bridging acetate ligands. The coordination geometry of the terminal CuII atom is square-pyramidal with a tetra­dentate ligand in the basal plane. The apical site is occupied by one O atom from an acetate ligand. The acetate-bridged Cu⋯Cu distance is 3.0910 (5) Å. An intra­molecular C—H⋯O hydrogen bond forms an S(6) ring motif. The crystal of the trinuclear complex is stabilized by C—H⋯O hydrogen bonds.