Coordination algorithms control molecular architecture: [CuI4(L2)4]4+ grid complex versus [MII2(L2)2X4]y+ side-by-side complexes (M=Mn,Co, Ni,Zn; X=solvent or anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3

The synthesis and characterisation of a pyridazine-containing two-armed grid ligand L2 (prepared from one equivalent of 3,6-diformylpyridazine and two equivalents of p-anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1-9) are reported. Single-crystal X-ray structure determinations revealed that the copper(I) complex had self-assembled as a [2 x 2] grid, [Cu(I) (4)(L2)(4)][PF(6)](4).(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25) (2.(CH(3)CN)(H(2)O)(CH(3)CH(2)OCH(2)CH(3))(0.25)), whereas the [Zn(2)(L2)(2)(CH(3)CN)(2)(H(2)O)(2)][ClO(4)](4).CH(3)CN (1.CH(3)CN), [Ni(II) (2)(L2)(2)(CH(3)CN)(4)][BF(4)](4).(CH(3)CH(2)OCH(2)CH(3))(0.25) (5 a.(CH(3)CH(2)OCH(2)CH(3))(0.25)) and [Co(II) (2)(L2)(2)(H(2)O)(2)(CH(3)CN)(2)][ClO(4)](4).(H(2)O)(CH(3)CN)(0.5) (6 a.(H(2)O)(CH(3)CN)(0.5)) complexes adopt a side-by-side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [Fe(II)(L2)(3)][Fe(III)Cl(3)OCl(3)Fe(III)].CH(3)CN (7.CH(3)CN). A more soluble salt of the cation of 7, the diamagnetic complex [Fe(II)(L2)(3)][BF(4)](2).2 H(2)O (8), was prepared, as well as two derivatives of 2, [Cu(I) (2)(L2)(2)(NCS)(2)].H(2)O (3) and [Cu(I) (2)(L2)(NCS)(2)] (4). The manganese complex, [Mn(II) (2)(L2)(2)Cl(4)].3 H(2)O (9), was not structurally characterised, but is proposed to adopt a side-by-side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side-by-side complexes: J=-21.6 cm(-1) and g=2.17 for S=1 dinickel(II) complex [Ni(II) (2)(L2)(2)(H(2)O)(4)][BF(4)](4) (5 b) (fraction monomer 0.02); J=-7.6 cm(-1) and g=2.44 for S= 3/2 dicobalt(II) complex [Co(II) (2)(L2)(2)(H(2)O)(4)][ClO(4)](4) (6 b) (fraction monomer 0.02); J=-3.2 cm(-1) and g=1.95 for S= 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7.H(2)O gave J=-75 cm(-1) and g=1.81 for the S= 5/2 diiron(III) anion (fraction monomer=0.025). These parameters are lower than normal for Fe(III)OFe(III) species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7.H(2)O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. M?ssbauer measurements at 77 K confirmed that there are two iron sites in 7.H(2)O, a low-spin iron(II) site and a high-spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.     

Cover Picture: Coordination Algorithms Control Molecular Architecture: [CuI4(L2)4]4+ Grid Complex Versus [MII2(L2)2X4]y+ Side‐By‐Side Complexes (M=Mn,Co, Ni,Zn; X=Solvent or Anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3] (Chem. Eur. J. 16/2003)

The cover picture shows how differing coordination algorithms control the molecular architecture of complexes of the pyridazine‐containing, two‐armed, acyclic Schiff base ligand L2 (left, prepared from one equivalent of 3,6‐diformylpyridazine and two equivalents of d‐anisidine). Two very different complexes of L2 self‐assemble from tetrahedral copper(I ) versus octahedral zinc(II ), nickel(II ), and cobalt(II ) controlled 1 : 1 reactions with L2. In both cases the metal ions are bridged by the pyridazine moieties in L2, but in the case of the tetrahedral copper(II ) the result is a tetrametallic [2×2] grid complex ([Cu^I₄(L2)⁴]⁴⁺: top right), whilst in the case of the octahedral metal(II ) ions dimetallic side‐by‐side complexes, [M^II₂(L2)²(X)₄]^y+ (M = Mn, Co, Ni, Zn; X = solvent or anion), are formed (bottom right). The cover image was kindly generated by M. Crawford (University of Otago) with Strata Studio Pro (Strata). More details are given by S. Brooker and co‐workers on p. 3772 ff.     

Alkoholyse von [Fe2(OtBu)6] als einfacher Weg zu neuen Eisen(III)‐Alkoxo‐Verbindungen: Synthesen und Kristallstrukturen von [Fe2(OtAmyl)6], [Fe5OCl(OiPr)12], [Fe5O(OiPr)13], [Fe5O(OiBu)13], [Fe5O(OCH2CF3)13], [Fe5O(OnPr)13] und [Fe9O3(OnPr)21] · iPrOH

Alcoholysis of [Fe₂(O^tBu)₆] as a Simple Route to New Iron(III)‐Alkoxo Compounds: Synthesis and Crystal Structures of [Fe₂(O^tAmyl)₆], [Fe₅OCl(OⁱPr)₁₂], [Fe₅O(OⁱPr)₁₃], [Fe₅O(OⁱBu)₁₃], [Fe₅O(OCH₂CF₃)₁₃], [Fe₅O(OⁿPr)₁₃], and [Fe₉O₃(OⁿPr)₂₁] · ⁿPrOH New alkoxo‐iron compounds can be synthesized easily by alcoholysis of [Fe₂(O^tBu)₆] ( 1 ). Due to different bulkyness of the alcohols used, three different structure types are formed: [Fe₂(OR)₆], [Fe₅O(OR)₁₃] and [Fe₉O₃(OR)₂₁] · ROH. We report synthesis and crystal structures of the compounds [Fe₅OCl(OⁱPr)₁₂] ( 2 ), [Fe₂(O^tAmyl)₆] ( 3 ), [Fe₅O(OⁱPr)₁₃] ( 4 ), [Fe₅O(OⁱBu)₁₃] ( 5 ), [Fe₅O(OCH₂CF₃)₁₃] ( 6 ), [Fe₉O₃(OⁿPr)₂₁] · ⁿPrOH ( 7 ) and [Fe₅O(OⁿPr)₁₃] ( 8 ). Crystallographic Data: 2 , tetragonal, P 4/n, a = 16.070(5) Å, c = 9.831(5) Å, V = 2539(2) ų, Z = 2, d_c = 1.360 gcm^?3, R₁ = 0.0636; 3 , monoclinic, P 2₁/c, a = 10.591(5) Å, b = 10.654(4) Å, c = 16.740(7) Å, β = 104.87(2)°, V = 1826(2) ų, Z = 2, d_c = 1.154 gcm^?3, R₁ = 0.0756; 4 , triclinic, , a = 20.640(3) Å, b = 21.383(3) Å, c = 21.537(3) Å, α = 82.37(1)°, β = 73.15(1)°, γ = 61.75(1)°, V = 8013(2) ų, Z = 6, d_c = 1.322 gcm^?3, R₁ = 0.0412; 5 , tetragonal, P 4cc, a = 13.612(5) Å, c = 36.853(5) Å, V = 6828(4) ų, Z = 4, d_c = 1.079 gcm^?3, R₁ = 0.0609; 6 , triclinic, , a = 12.039(2) Å, b = 12.673(3) Å, c = 19.600(4) Å, α = 93.60(1)°, β = 97.02(1)°, γ = 117.83(1)°, V = 2600(2) ų, Z = 2, d_c = 2.022 gcm^?3, R₁ = 0.0585; 7 , triclinic, , a = 12.989(3) Å, b = 16.750(4) Å, c = 21.644(5) Å, α = 84.69(1)°, β = 86.20(1)°, γ = 77.68(1)°, V = 4576(2) ų, Z = 2, d_c = 1.344 gcm^?3, R₁ = 0.0778; 8 , triclinic, , a = 12.597(5) Å, b = 12.764(5) Å, c = 16.727(7) Å, α = 91.94(1)°, β = 95.61(1)°, γ = 93.24(2)°, V = 2670(2) ų, Z = 2, d_c = 1.323 gcm^?3, R₁ = 0.0594.     

A family of calix[4]arene-supported [Mn(III)2Mn(II)2] clusters

In the cone conformation calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition-metal centres. Reaction of these molecules with manganese salts in the presence of an appropriate base (and in some cases co-ligand) results in the formation of a family of calixarene-supported [Mn(III)(2)Mn(II)(2)] clusters that behave as single-molecule magnets (SMMs). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs.     

Giant polyniobate clusters based on [Nb7O22]9- units derived from a Nb6O19 precursor

Rational self-assembly of hexaniobate Lindqvist-type precursor [HNb6O19]7- with soluble Cu2+ salts utilizing different strategies produces a series of giant polyniobate clusters, namely, (H2en)1.25[Cu(en)2(H2O)]2Cl4[Nb24O72H21.5]7 H2O (1; en: ethylenediamine), [Cu(en)2]3[Cu(en)2(H2O)]9[{H2Nb6O19} subset{[({KNb24O72H10.25}{Cu(en)2})2{Cu3(en)3(H2O)3}{Na1.5Cu1.5(H2O)8}{Cu(en)2}4]6}]144 H2O (2), K12Na4[H23NaO8Cu24(Nb7O22)8]106 H2O (3), and K16Na12[H9Cu25.5O8(Nb7O22)8] 73.5 H2O (4). Their structures were determined and further characterized by single-crystal X-ray diffraction analysis, IR and Raman spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Structural analyses reveal that compound 2 comprises a giant capsule anion based on a wheel-shaped cluster encapsulating a Lindqvist diprotonated cluster [H2Nb6O19]6- unit, and forms a honeycomb-like structure with the inclusion of Lindqvist-type anions [H2Nb6O19]6- in the holes, whereas 3 and 4 represent an unprecedented giant cube-shaped framework. All the compounds are built from [Nb7O22]9- fundamental building blocks. Solution Raman spectroscopy studies of 2 and 3 reveal that the solid-state structures of these polyniobate cluster anions disassemble and exist in the form of the [Nb6O19]8- unit in solution. Magnetic susceptibility measurement of 3 shows antiferromagnetic coupling interactions between CuII ions with the spin-canting phenomenon.     

Sliding Polymeric Layers and Anion Displacement Coupled with Spin Crossover in Two-Dimensional Networks of [Fe(hbtz)2(CH3CN)2](BF4)2

The abrupt high spin (HS)→low spin (LS) transition (T^↓_1/2=136 K) in [Fe(hbtz)₂(CH₃CN)₂](BF₄)₂ (hbtz=1,6-di(tetrazol-2-yl)hexane) is finished at 100 K and further thermal treatment influences the spin crossover. Subsequent heating involves a change of the spin state in the same way (T^↑_1/2=136 K) on cooling. In contrast, cooling below 100 K triggers different behavior and T^↑_1/2 is shifted to 170 K. The extraordinary structural changes that occurred below 100 K are responsible for the observed diversity of properties. A unique feature of the low-temperature phase is the rebuilding of the anion network expressed by a shift of anions inside the polymeric layer at a distance of 1.2 Å as well as the relative shift of neighboring layers at over 4 Å. These structural alterations, connected with a phase transition, become the origin of the strain, which in most cases causes crystal cleaving. In a sample composed from crystals crushed as a result of the phase transition or as a result of mechanical crumbling, the hysteresis loop vanishes; however, annealing the sample allows to its partial restoration. A replacement of acetonitrile by other nitriles leads to preservation of the polymeric structure and spin crossover, but no phase transition follows.     

Alkoxo‐Verbindungen des dreiwertigen Eisen: Synthese und Charakterisierung von [Fe2(OtBu)6], [Fe2Cl2(OtBu)4], [Fe2Cl4(OtBu)2] und [N(nBu)4]2[Fe6OCl6(OMe)12]

Alkoxo Compounds of Iron(III): Syntheses and Characterization of [Fe₂(OtBu)₆], [Fe₂Cl₂(OtBu)₄], [Fe₂Cl₄(OtBu)₂] and [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] The reaction of iron(III)chloride in diethylether with sodium tert‐butylat yielded the homoleptic dimeric tert‐‐butoxide Fe₂(OtBu)₆ ( 1 ). The chloro‐derivatives [Fe₂Cl₂(OtBu)₄] ( 2 ), and [Fe₂Cl₄(OtBu)₂] ( 3 ) could be synthesized by ligand exchange between 1 and iron(III)chloride. Each of the molecules 1 , 2 , and 3 consists of two edge‐sharing tetrahedrons, with two tert‐butoxo‐groups as μ₂‐bridging ligands. For the synthesis of the alkoxides 1 , 2 , and 3 diethylether plays an important role. In the first step the dietherate of iron(III)chloride FeCl₃(OEt₂)₂ ( 4 ) is formed. The reaction of iron(III)chloride with tetrabutylammonium methoxide in methanol results in the formation of a tetrabutylammonium methoxo‐chloro‐oxo‐hexairon cluster [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] ( 5 ). Crystal structure data: 1 , triclinic, P1¯, a = 9.882(2) Å, b = 10.523(2) Å, c = 15.972(3) Å, α = 73.986(4)°, β = 88.713(4)°, γ = 87.145(4)°, V = 1594.4(5) ų, Z = 2, d_c = 1.146 gcm^—1, R₁ = 0.044; 2 , monoclinic, P2₁/n, a = 11.134(2) Å, b = 10.141(2) Å, c = 12.152(2) Å und β = 114.157(3)°, V = 1251.8(4) ų, Z = 2, d_c = 1.377 gcm^—1, R₁ = 0.0581; 3 , monoclinic, P2₁/n, a = 6.527(2) Å, b = 11.744(2) Å, c = 10.623(2), β = 96.644(3)°, V = 808.8(2) ų, Z = 2, d_c = 1.641 gcm^—1, R₁ = 0.0174; 4 , orthorhombic, Iba2, a = 23.266(5) Å, b = 9.541(2) Å, c = 12.867(3) Å, V = 2856(2) ų, Z = 8, d_c = 1.444 gcm^—1, R₁ = 0.0208; 5 , trigonal, P3₁, a = 13.945(2) Å, c = 30.011(6) Å, V = 5054(2) ų, Z = 6, d_c = 1.401 gcm^—1; R_c = 0.0494.     

Self-assembly of the octanuclear cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ and the one-dimensional N-propylcarbamate-linked coordination polymer {[Cu(O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n

The reaction of Cu(ClO4)2.6-H2O and n-propylamine in methanol gives two high-nuclearity products of well-defined compositions. At amine concentrations greater than seven equivalents compared to copper ion concentration, the system fixes carbon dioxide from air to form the one-dimensional carbamate-bridged coordination polymer, {[Cu(mu2-O,O'-O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n ({1-ClO4}n). Lower relative amine concentrations lead to the self-assembly of an octanuclear copper-amine-hydroxide cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ (2). Both compounds exhibit unique structures: {1-ClO4}n is the first mu2-O,O'-mono-N-alkylcarbamate-linked coordination polymer and 2 is the largest copper-hydroxide-monodentate amine cluster identified to date. The crystal structures indicate that the size of the n-propyl group is probably crucial for directing the formation of these compounds. Magnetic susceptibility studies indicate very weak antiferromagnetic coupling for 1. The octanuclear cluster 2 displays slightly stronger net antiferromagnetic coupling, despite the presence of a number of Cu-O(H)-Cu angles below the value of about 97 degrees that would normally be expected to yield ferromagnetic coupling.     

Enantioselective self-assembly of bimetallic [Mn(II) (delta)-Cr(III)(C2O4)3]- and [Mn(II) (lambda)-Cr(III)(C2O4)3]- layered anionic networks templated by the optically active (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ions

The ferrocenic ammonium (Rp)- and (Sp)-[1-CH2NR(3-)-2-CH3-C5H3Fe-C5H5] iodide salts with R=CH3, C2H5, n-C3H7, n-C4H9, were synthesized starting from the (Rp)- and (Sp)-[1-CH2N(CH3)2-2-CH3-C5H3Fe-C5H5] amines obtained in their optically active forms through asymmetric cyclopalladation of [C5H5Fe-C5H4CH2N(CH3)2]. 1H NMR studies of these planar chiral 1,2-disubstituted ferrocenic ammonium iodide salts in the presence of the (Delta)-(tris(tetrachlorobenzenediolato)phosphate(V) anion), [(Delta)-Trisphat] support the formation of specific diastereomeric ion pairs. Such intermolecular interactions can be related to the self-assembly of the two-dimensional optically active compounds [[(Sp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Delta)-Cr(C2O4)3]] and [[(Rp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Lambda)-Cr(C2O4)3]] starting from the resolved (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ion associated to the racemic anionic building block rac-[Cr(C2O4)3]3- and Mn2+. Both enantiomeric forms of the networks behave as ferromagnets with a Curie temperature of 5.7 K.