Synthesis and characterization of [Fe(III)(qsal)2][M(III)(pds)2] (M = Cu, Au)

Salts of the Fe(III) spin crossover cation [Fe^III(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine) and monoanions [M^III(pds)₂]⁻ (M = Cu, Au; pds = pirazine-2,3-diselenolate) with formula [Fe^III(qsal)₂][M^III(pds)₂] were prepared and characterized by single crystal X-ray diffraction and magnetic measurements. These two salts present magnetic properties essentially due to the Fe^III centres in the high-spin state (S = 5/2), and do not have any spin transition.     

The cyanocarbanion (C[C(CN)2]3) as monodentate ligand: Synthesis, structure and magnetic properties of [Mn2(bpym)3(tcpd)2(H2O)2] (tcpd = (C[C(CN)2]3) and bpym = 2,2′-bipyrimidine)

One-pot reaction between MnCl₂·4H₂O, K₂tcpd (tcpd²⁻ = [C₁₀N₆]²⁻ = (C[C(CN)₂]₃)²⁻ = 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide anion) and 2,2′-bipyrimidine (bpym = C₈H₆N₄) in aqueous solution yields the new compound [Mn₂(bpym)₃(tcpd)₂(H₂O)₂] (1). The molecular structure of 1 consists of a centrosymmetrical binuclear complex which includes unprecedented unidentate tcpd ligands with two bidentate and a bis-chelate bpym units. Examination of the intermolecular distances reveals that the dinuclear units are held together by hydrogen bonds involving coordinated water molecules and two nitrile groups of the tcpd ligand, giving rise to a 2D structure overall. Variable-temperature magnetic susceptibility data show the occurrence of slight antiferromagnetic coupling (J = −0.58 cm⁻¹) between the Mn(II) ions through bridging bpym (the exchange Hamiltonian being defined as ).     

BEDT-TTF salts of the unsymmetrical [M(tfadt)2] dithiolene complexes (M = Ni, Au; tfadt = S2C2(CN)(CF3))

Two closely related 1:1 salts are obtained upon electrocrystallization of BEDT-TTF (BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene) in the presence of the isosteric [M(tfadt)₂]⁻ dithiolene complexes (tfadt: 1-trifluoromethyl-2-cyano-1,2-dithiolato), which essentially differ by their spin state, S = 0 in [Au(tfadt)₂]⁻, S = 1/2 in [Ni(tfadt)₂]⁻. In both [BEDT-TTF][M(tfadt)₂] salts, the BEDT-TTF radical cations form chains with a strong lateral overlap and strong antiferromagnetic interactions while the paramagnetic anions in the nickel-containing salt [BEDT-TTF][Ni(tfadt)₂] are essentially non-interacting. The structural differences between the nickel and gold complexes are analyzed and discussed.     

TTF charge transfer salts containing cyanometallate anions [M(phen)(CN)4] (M = Cr or Fe; phen = 1,10-phenanthroline)

Two new charge transfer salts of TTF with the counter anions [M(phen)(CN)₄]⁻ (phen = 1,10-phenanthroline, M = Cr (I) and Fe (II)) are described. The structures consist of alternating stacks of dimerised TTF⁺ cations and [M(phen)(CN)₄]⁻ anions and they are linked together by many short S?S contacts and hydrogen bonds. Within the organic stack, two dimerised TTF⁺ cations are arranged in a slipped face-to-face mode with short intra-dimer and long inter-dimer S?S distances. Strong antiferromagnetic exchange was found in the TTF⁺ dimers. Conductivity measurements show that compound I is a semiconductor.     

Spin-crossover iron(II) complexes [Fe(Medpq)(py)2(NCS)2] and [Fe(Medpq)(py)2(NCSe)2]: syntheses, characterization and magnetic properties

Two new spin-crossover complexes, [Fe(Medpq)(py)₂(NCS)₂] · py · 0.5H₂O (1) and [Fe(Medpq)(py)₂(NCSe)₂] · py (2) (Medpq = 2-methyldipyrido[3,2-f:2′,3′-h]-quinoxaline, py = pyridine), have been synthesized. The crystal structures were determined at both room temperature (298 K) and low temperature (110 K). Complexes 1 and 2 crystallize in the orthorhombic space group Pbca and monoclinic space group P2₁/n, respectively. In both complexes, the distorted [FeN₆] octahedron is formed by six nitrogen atoms from Medpq, the trans pyridine molecules and the cis NCX⁻ groups. The thermal spin transition is accompanied by the shortening of the mean Fe–N distances by 0.194 Å for 2. The mononuclear [Fe(Medpq)(py)₂(NCS)₂] and [Fe(Medpq)(py)₂(NCSe)₂] neutral species interact each other via π-stacking, resulting in a one-dimensional extended structure for both 1 and 2. There exist C–HX (X = S, Se) hydrogen bonds for both complexes. Variable-temperature magnetic susceptibility measurements and Mössbauer spectroscopy reveal the occurrence of a gradual spin transition. The transitions are centered at T_1/2 = 120 K for 1 and T_1/2 = 180 K for 2, respectively.     

Syntheses, crystal structures, and magnetic properties of two cyclic dimer M2L2 complexes constructed from a new nitronyl nitroxide ligand and M(hfac)2 (M = Cu, Mn)

Two new binuclear radical complexes derived from a new long nitronyl nitroxide ligand, 2-[4-(5-pyrimidyl)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (4-NITPhPyrim), and M(hfac)₂ (M²⁺ = Cu²⁺, Mn²⁺; hfac⁻ = hexafluoroacetylacetonato), [Cu(hfac)₂(4-NITPhPyrim)]₂ · 4H₂O (1) and [Mn(hfac)₂(4-NITPhPyrim)]₂ · 4H₂O (2), were synthesized as well as characterized structurally and magnetically. X-ray analysis indicates that 1 and 2 are rectangle-like centrosymmetric dimer M₂L₂ complexes. Magnetic measurements indicate that there are two types of magnetic exchanges in 1: the ferromagnetic (FM) exchange between the Cu(II) ion and the directly bonded nitroxide unit (J₁ = 24.20 cm⁻¹) and the weak FM exchange of Cu-NIT through the pyrimidine and phenyl rings (J₂ = 0.62 cm⁻¹). Besides the strong antiferromagnetic (AFM) coupling between the Mn(II) ion and the directly bonded nitroxide unit (J = −87.61 cm⁻¹), there is a weak FM interaction between the two Mn-NIT pairs (θ = 0.39 K) in 2.     

Synthesis, spectral and magnetical characterization of monomeric [Cu(2-NO2bz)2(nia)2(H2O)2] and structural analysis of similar [Cu(RCOO)2(L-N)2(H2O)2] complexes

A new complex of composition [Cu(2-NO₂bz)₂(nia)₂(H₂O)₂] (1) (nia = nicotinamide, 2-NO₂bz = 2-nitrobenzoate) has been prepared and its composition and stereochemistry as well as coordination mode have been determined by elemental analysis, electronic, infrared and EPR spectroscopy, magnetization measurements over the temperature range 1.8-300 K, and its structure has been solved, as well. The complex structure consists of the centrosymmetric molecules with Cu(II) atom monodentately coordinated by the pair of 2-nitrobenzoato anions and by the pair of nicotinamide molecules, forming nearly tetragonal basal plane, and by a pair of water molecules that complete tetragonal-bipyramidal coordination polyhedron about the copper atom. The complex 1 exhibits magnetic moment μ_eff = 1.86 B.M. at 300 K which decreases to μ_eff = 1.83 B.M. at 1.8 K. The magnetic susceptibility temperature dependence obeys Curie-Weiss law with Curie constant of 0.442 cm³ K mol⁻¹ and with Weiss constant of −1.0 K. EPR spectra at room temperature as well as at 77 K are of axial type with g_⊥ = 2.065 and g_∥ = 2.280 and exhibit clearly, but partially resolved parallel hyperfine splitting with A_II = 160 G, that is consistent with the determined molecular structure of 1. In order to analyze the factors influencing the degree of tetragonal distortion of coordination polyhedron, the dataset of 72 structures similar to that of 1 was extracted from CCD and analyzed. A significant correlation between the average Cu-O_ax bond length and tetragonality parameter τ which was found as a consequence of the Jahn-Teller effect.     

Dioxouranium complexes as ligand. Synthesis and characterization of sandwich-type polyoxometalates [X2W18(UO2)2{(H2O)3M}2O68] (X = As and P) (M = Co, Cu, Mn, Ni and Zn)

The title complexes are synthesized by the reaction of an unusual ligand of [K₂P₂W₁₈(UO₂)₂O₆₈]¹²⁻ (1) and [KAs₂W₁₈(UO₂)₂O₆₈]¹³⁻ (2) with divalent metal ions of Co^II, Cu^II, Mn^II, Ni^II and Zn^II in 1:2 mole ratio and are characterized by elemental analysis, IR, ³¹P NMR, UV-Vis spectroscopy, TGA, and single crystal structure analysis. Crystals of [P₂W₁₈(UO₂)₂{(H₂O)₃Co}₂O₆₈]¹⁰⁻ (1a) and [As₂W₁₈(UO₂)₂{(H₂O)₃Cu}₂O₆₈]¹⁰⁻ (2b) are orthorhombic space group Cmca. Both 1a and 2b have structures in which two [M(H₂O)₃] (M = Co^II, Cu^II) and two UO₂ groups are sandwiched between two symmetry equivalent (XW₉) (X = P, As) units in a virtual C_i symmetry. In solution, 1a and [P₂W₁₈(UO₂)₂{(H₂O)₃Zn}₂O₆₈]¹⁰⁻ (1d) give two-line P NMR spectra that are consistent with a C_s symmetry structures so, are not consistent with the solid-state structures. The sodium salts of them give one-line P NMR spectra and are consistent with the C_i symmetry of solid-state structures. The uranium atoms have pentagonal-bipyramidal coordination, achieved by three equatorial bonds to the one XW₉ and two bonds to the other. The M atoms have octahedral or square pyramidal coordination, but only one bond to the one XW₉ and one bond to the other.     

Two cyano-bridged heterotrinuclear complexes built from [(Tp)Fe(CN)3] (Tp = hydrotris(pyrazolyl)borate): synthesis, crystal structures and magnetic properties

Using an anionic precursor [(Tp)Fe^III(CN)₃]⁻ (1) as a building block, two cyano-bridged centrosymmetric heterotrinuclear complexes, (2) and (3) (en = ethylenediamine), have been synthesized and structurally characterized. In each complex, [TpFe(CN)₃]⁻ acts as a monodentate ligand toward a central [Mn(C₂H₅OH)₄]²⁺ or [Ni(en)₂]²⁺ core through one of its three cyanide groups, the other two cyanides remaining terminal. The intramolecular Fe-Mn and Fe-Ni distances are 5.2354(4) and 5.0669(11) Å, respectively. The magnetic properties of complexes 2 and 3 have been investigated in the temperature range of 2.0-300 K. A weak antiferromagnetic interaction between the Mn(II) and Fe(III) ions has been found in complex 2. The magnetic data of 2 can be fitted with the isotropic Hamiltonian: where J and J′ are the intramolecular exchange coupling parameters between adjacent and peripheral spin carriers, respectively. This leads to values of J = −1.37 cm⁻¹ and g = 2.05. The same fitting method is applied to complex 3 to give values of J = 1.2 cm⁻¹ and g = 2.25, showing that there is a ferromagnetic interaction between the Fe(III) and Ni(II) ions.     

A trinuclear copper(II) complex with 2,5-pyridine-dicarboxylato bridges - [Cu3(2,5-pydc)2(Me5dien)2(H2O)2(BF4)2] · H2O: Synthesis, crystal structure and magnetic properties

A trinuclear copper(II) complex, [Cu₃(2,5-pydc)₂(Me₅dien)₂(BF₄)₂(H₂O)₂] · H₂O 1, has been constructed from 2,5-pyridine-dicarboxylato bridges (2,5-pydc²⁻) and N,N,N′,N″,N″-pentamethyl-diethylenetriamine (Me₅dien) acting as a blocking ligand. The copper ions, within the centrosymmetric trinuclear cations, are connected by two 2,5-pydc²⁻ bridges, with an intramolecular Cu···Cu separation of 8.432 Å. The central copper ion exhibits an elongated octahedral geometry, with semicoordinated ions, while the terminal ones are pentacoordinated (distorted square-pyramidal geometry). The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the copper(II) ions (J = −5.9 cm⁻¹, H = −JS_Cu1S_Cu2 − JS_Cu2S_Cu1a).     

Synthesis and characterization of deuterium-labelled (fulvene)M(CO)3 complexes (M = Cr, Mo)

The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)₃ (M = Cr, Mo) complexes is reported. (η⁵-6-Dimethylaminofulvene-d₂)Cr(CO)₃ and (η⁵-6-dimethylaminofulvene-d₂)Mo(CO)₃ were obtained in high yields by reacting the deuterated fulvene ligands with (MeCN)₃M(CO)₃ (M = Cr, Mo). In addition, syntheses of 6,6-diphenylfulvene-d₁₀ and 6,6-diphenyl-1,2-benzofulvene-d₁₀ as well as the corresponding tricarbonylchromium complexes are described.     

Solvothermal synthesis, crystal structure and magnetic property of a new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N3)2]2 (2,2′-dpa = 2,2′-dipicolylamine)

A new dinuclear manganese(II)-azido complex: [Mn(2,2′-dpa)(N₃)₂]₂1 (2,2′-dpa = 2,2′-dipicolylamine) has been synthesized solvothermally. X-ray crystallography analysis reveals that it consists of two crystallographically independent dimeric manganese moieties; each manganese(II) atom is coordinated by one 2,2′-dipicolylamine, one terminal azido ligand, and double end-on bridging azido ligands, exhibiting a slightly distorted octahedral sphere. There are extensive short contacts among dimeric manganese moieties, which extend the structure into an interesting three-dimensional supramolecular array. Magnetic determination of 1 indicates that dominant ferromagnetic interaction and weak antiferromagnetic interaction, which are ascribed to the end-on azido bridges and the short contacts, respectively, co-exist in this complex.     

A hexanuclear iron(III) complex [Fe6O2(OH)2(PhCOO)10(hedmp)2]·3CH3CN assembled from 2-hydroxyethyl-3,5-dimethyl pyrazole

In order to assemble polynuclear iron(III) complexes, the coordination chemistry of the 2-hydroxyethyl-3,5-dimethylpyrazole (hedmp-H) ligand has been investigated. Reaction of hedmp-H with trinuclear iron carboxylate precursor [Fe₃O(PhCOO)₆(H₂O)₃]Cl in acetonitrile yielded the hexanuclear Fe(III) complex [Fe₆O₂(OH)₂(PhCOO)₁₀(hedmp)₂]·3CH₃CN (1). This aggregate has been characterized by employing various analytical techniques, spectroscopic studies and single crystal X-ray diffraction. Detailed magnetic susceptibility measurements revealed that 1 displays an S_T = 5 ground state.     

Rhenium(IV) cyanate complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReBr4(OCN)(DMF)] and (NBu4)2[ReBr(OCN)2(NCO)3]

Two new rhenium(IV) mononuclear compounds of formula NBu₄[ReBr₄(OCN)(DMF)] (1) and (NBu₄)₂[ReBr(OCN)₂(NCO)₃] (2) (NBu₄ = tetrabutylammonium cation, OCN = O-bonded cyanate anion, NCO = N-bonded cyanate anion and DMF = N,N-dimethylformamide) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 crystallizes in the monoclinic system with the space group P2₁/n, whereas 2 crystallizes in the triclinic one with as space group. In both complexes the rhenium atom is six-coordinated, in 1 by four Br atoms in the equatorial plane, and two trans-oxygen atoms, one of a DMF molecule and another one from a cyanato group, while in 2 by one bromide anion and five cyanate ligands, two of which are O-bonded and three N-bonded, forming a somewhat distorted octahedral surrounding. Magnetic susceptibility measurements on polycrystalline samples of 1 and 2 in the temperature range 1.9-300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field splitting (|2D| is ca. 41.6 and 39.2 cm⁻¹ for 1 and 2, respectively).     

A new mixed-valence hexanuclear cobalt complex, [Co4Co2(dea)2(Hdea)4)(piv)4](ClO4)2·H2O: Synthesis, crystal structure and magnetic properties

A new Co^II/Co^III hexanuclear complex, [Co₄^IICo₂^III(dea)₂(Hdea)₄)(piv)₄](ClO₄)₂·H₂O 1, has been obtained by reacting cobalt(II) perchlorate, diethanolamine, and pivalic acid (H₂dea = diethanolamine and piv = pivalato anion). The cobalt ions are held together by four μ₃ and four μ₂ alkoxo bridges as well as by four syn-syn carboxylato groups. The hexanuclear motif contains four Co(II) and two Co(III) ions. The {Co^II₄Co^III₂(μ₂-O)₄(μ₃-O)₄} core can be described as a four face-sharing monovacant and bivacant distorted heterocubane units. The cobalt(III) ions are hexacoordinated. Two of the cobalt(II) are hexacoordinated, while the two others are pentacoordinated with a bipyramidal stereochemistry. The magnetic properties of 1 have been investigated in the temperature range 1.9-300 K. Compound 1 exhibits an overall antiferromagnetic behaviour with a ground singlet spin state.     

3D hydrogen bonded metal-organic frameworks constructed from [M(H2O)6][M′(dipicolinate)2] · mH2O (M/M′ = Zn/Ni or Ni/Ni). Identification of intercalated acyclic (H2O)6/(H2O)10 clusters

New heterodinuclear Zn^II/Ni^II (1) and homodinuclear Ni^II/Ni^II (2) water-soluble and air stable compounds of general formula [M(H₂O)₆][M′(dipic)₂] · mH₂O have been easily prepared by self-assembly of the corresponding metal(II) nitrates with dipicolinic acid (H₂dipic) in water solution at room temperature.  The compounds have been characterized by IR, UV/Vis and atomic absorption spectroscopies, elemental and X-ray single crystal diffraction (for 1 · 4H₂O and 2 · 5H₂O) analyses.  3D infinite polymeric networks are formed via extensive hydrogen bonding interactions involving all coordinated and crystallization water molecules, and all dipicolinate oxygens, thus contributing to additional stabilization of dimeric units, metal-organic chains and 2D layers.  In 1 · 4H₂O, the latter represent a rectangular-grid 2D framework with multiple channels if viewed along the c crystallographic axis, while in 2 · 5H₂O intercalated crystallization water molecules are associated to form acyclic nonplanar hexameric water clusters and water dimers which occupy voids in the host metal-organic matrix, with a structure stabilizing effect via host-guest interactions.  The hexameric cluster extends to the larger (H₂O)₁₀ one with an unusual geometry (acyclic helical octamer with two pendent water molecules) by taking into account the hydrogen bonds to water ligands in [Ni(H₂O)₆]²⁺.  The obtained Zn/Ni compound 1 relates to the recently reported family of heterodimetallic complexes [M(H₂O)₅M′(dipic)₂] · mH₂O (M/M′ = Cu/Co, Cu/Ni, Cu/Zn, Zn/Co, Ni/Co, m = 2, 3), what now allows to establish the orders of the metal affinity towards the formation of chelates with dipicolinic acid (Co^II > Ni^II > Zn^II > Cu^II) or aqua species (Co^II < Ni^II < Zn^II < Cu^II).     

Mn(II) complexes of monoanionic bidentate chelators: X-ray crystal structures of Mn(dha)2(CH3OH)2 (Hdha = dehydroacetic acid) and [Mn(ema)2(H2O)]2 · 2H2O (Hema = 2-ethyl-3-hydroxy-4-pyrone)

This report describes synthesis and characterization of bis-ligand Mn(II) complexes of bidentate chelators: maltol (3-hydroxy-2-methyl-4-pyrone), ethylmaltol (2-ethyl-3-hydroxy-4-pyrone), 1,2-dimethyl-3-hydroxy-4-pyridinone (DMHP) and dehydroacetic acid. All four Mn(II) complexes were characterized by elemental analysis, IR, UV/Vis, EPR, cyclic voltammetry, and X-ray crystallography in cases of Mn(dha)₂(CH₃OH)₂ and [Mn(ema)₂(H₂O)]₂ · 2H₂O. The bidentate chelator plays a significant role in the solid state structure of its Mn(II) complex. For example, dha forms the monomeric complex Mn(dha)₂(CH₃OH)₂ while ethylmaltol forms the dimeric complex [Mn(ema)₂(H₂O)]₂. Because of smaller size, maltol ligands in Mn(ma)₂ are able to bridge adjacent Mn(II) centers to give a polymeric structure in solid state. Despite of the difference in their solid state structures, both Mn(ema)₂ and Mn(ma)₂ exist in solution as monomeric Mn(II) species, Mn(ema)₂(H₂O)₂ and Mn(ma)₂(H₂O)₂. This assumption is supported by the similarity in their UV/Vis spectra, EPR data and electrochemical properties. Replacing maltol with DMHP results in a decrease (by ∼100 mV) in the redox potential for the Mn(II)/Mn(III) couple, suggesting that DMHP stabilizes Mn(III) better than maltol. Since Mn(DMHP)₂(H₂O)₂ is readily oxidized to form the more stable Mn(III) complex Mn(DMHP)₃, DMHP has the potential as a chelator for removal of excess Mn(II) from patients with chronic Mn toxicity.     

Reaction of [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) compounds with N1-alkylpyridylpyrazole-derived ligands

Palladium(II) and platinum(II) complexes with N-alkylpyridylpyrazole-derived ligands, 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L¹) and 2-(1-octyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L²), cis-[MCl₂(L)] (M = Pd(II), Pt(II)), have been synthesised. Treatment of [PdCl₂(L)] (L = L¹, L²) with excess of ligand (L¹, L²), pyridine (py) or triphenylphosphine (PPh₃) in the presence of AgBF₄ and NaBPh₄ produced the following complexes: [Pd(L)₂](BPh₄)₂, [Pd(L)(py)₂](BPh₄)₂ and [Pd(L)(PPh₃)₂](BPh₄)₂. All complexes have been characterised by elemental analyses, conductivity, IR and NMR spectroscopies. The crystal structures of cis-[PdCl₂(L²)] (2) and cis-[PtCl₂(L¹)] (3) were determined by a single crystal X-ray diffraction method. In both complexes, the metal atom is coordinated by one pyrazole nitrogen, one pyridine nitrogen and two chlorine atoms in a distorted square-planar geometry. In complex 3, π-π stacking between pairs of molecules is observed.     

Transition metal halide salts of 8-methylquinolinium: Synthesis and structures of (8-methylquinolinium)2 MX4·nH2O (M = Cu, Co, Zn; X = Cl, Br; n = 0, 1)

The reactions of metal(II) chlorides and bromides with 8-methylquinoline (8-mequin) in neutral and acidic solutions were investigated. The reaction with ZnCl₂, ZnBr₂, CoCl₂, CoBr₂, CuCl₂ or CuBr₂ with the appropriate HX in water or aqueous ethanol gave complexes of the formula (8-mequin)₂MX₄ (1, M = Cu, X = Cl; 2, M = Cu, X = Br; 3, M = Co, X = Cl; 4, M = Co, X = Br) or (8-mequin)₂ZnX₄·nH₂O (5, X = Cl, n = 0; 6, X = Br, n = 0; 7, X = Cl, n = 1; 8, X = Br, n = 1). Crystals of 1, 2 and 4-8 suitable for single crystal X-ray diffraction were obtained and the structures reported. Compounds 1 and 2 crystallize in the monoclinic space group C2/c, while 4-8 crystallize in the triclinic space group, . Variable temperature magnetic susceptibility data indicate very weak interactions for the copper compounds 1 and 2, while the magnetic behavior of 3 and 4 is dominated by single ion anisotropy, with weaker antiferromagnetic interactions.     

Structural and magnetic properties of one-dimensional coordination polymers {trans-[Ru(CN-Bu)4(CN)2]FeX3}n vs. molecular squares {cis-[Ru(CN-Bu)4(CN)2]FeX3}2 (X = NO3, Cl)

The reaction of cis- or trans-[Ru(CN^tBu)₄(CN)₂] with Fe(III) compounds leads to the formation of molecular squares of the general formula cyc-[Ru(CN-^tBu)₄(CN)₂FeX₃]₂ or one-dimensional coordination polymers [Ru(CN-^tBu)₄(CN)₂FeX₃]_n, respectively. Temperature dependent susceptibility measurements indicate that the magnetic properties of the coordination compounds are determined by their molecular structure. Of particular importance is the local symmetry at the iron(III) center which is related to the coordinating anion. The magnetic properties are best described in terms of weak antiferromagnetic interactions between the iron centers for the molecular squares as well as the coordination polymer with X = NO₃ and as weak ferromagnetic interactions in case of the linear coordination polymer with X = Cl. For all compounds zero field splitting at low temperatures has to be taken into account.