Magnetic spongelike behavior of 3D ferrimagnetic {[Mn(II)(imH)]2[Nb(IV)(CN)8]}n with Tc = 62 K

Fully reversible room temperature dehydration of 3D {Mn(II)2(imH)2(H2O)4[Nb(IV)(CN)8] x 4 H2O}n (1; imH = imidazole) of Tc = 25 K results in the formation of 3D ferrimagnet {[Mn(II)(imH)]2[Nb(IV)(CN)8]}n (2), with Tc = 62 K, the highest ever known for octacyanometalate-based compounds. The dramatic magnetostructural modifications in 2 provide the first example of magnetic spongelike behavior in an octacyanometallate-based assembly.     

Synthesis, characterization, and photoresponsive properties of a series of Mo(IV)-Cu(II) complexes

Six Mo(IV)-Cu(II) complexes, [Cu(tpa)](2)[Mo(CN)(8)]·15H(2)O (1, tpa = tris(2-pyridylmethyl)amine), [Cu(tren)](2)[Mo(CN)(8)]·5.25H(2)O (2, tren = tris(2-aminoethyl)amine), [Cu(en)(2)][Cu(0.5)(en)][Cu(0.5)(en)(H(2)O)][Mo(CN)(8)]·4H(2)O (3, en = ethylenediamine), [Cu(bapa)](3)[Mo(CN)(8)](1.5)·12.5H(2)O (4, bapa = bis(3-aminopropyl)amine), [Cu(bapen)](2)[Mo(CN)(8)]·4H(2)O (5, bapen = N,N'-bis(3-aminopropyl)ethylenediamine), and [Cu(pn)(2)][Cu(pn)][Mo(CN)(8)]·3.5H(2)O (6, pn = 1,3-diaminopropane), were synthesized and characterized. Single-crystal X-ray diffraction analyses show that 1-6 have different structures varying from trinuclear clusters (1-2), a one-dimensional belt (3), two-dimensional grids (4-5), to a three-dimensional structure (6). Magnetic and ESR measurements suggest that 1-6 exhibit thermally reversible photoresponsive properties on UV light irradiation through a Mo(IV)-to-Cu(II) charge transfer mechanism. A trinuclear compound [Cu(II)(tpa)](2)[Mo(V)(CN)(8)](ClO(4)) (7) was synthesized as a model of the photoinduced intermediate.     

The first coordination polymers and hydrogen bonded networks containing octahedral Nb6 clusters and alkaline earth metal complexes

Three novel coordination polymers built of octahedral niobium cyanochloride clusters [Nb6Cl12(CN)6] and alkaline earth metal complexes have been prepared by reaction of aqueous solutions of (Me4N)4Nb6Cl18 and KCN with solutions of alkaline earth metal salts and 1,10-phenanthroline (phen) (1:2 molar ratio) in H2O/EtOH. The structures of [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] x (phen)(EtOH)1.6 (1), [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] x (phen)2 x 4H2O (2), and [Ba(phen)2(H2O)]2[Nb6Cl12(CN)6] (3) were determined by single-crystal X-ray diffraction. The three compounds were found to crystallize in the monoclinic system (space group Pn) with a = 11.5499(6) A, b = 17.5305(8) A, c = 21.784(1) A, beta = 100.877(1) degrees for 1; triclinic system (P1) with a = 12.609(4) A, b = 13.262(4) A, c = 16.645(5) A, alpha = 69.933(6) degrees, beta = 68.607(6) degrees, gamma = 63.522(5) degrees for 2; and a = 16.057(1) A, b = 16.063(1) A, c = 16.061(1) A, alpha = 86.830(1) degrees, beta = 64.380(1) degrees, gamma = 67.803(1) degrees for 3. Compounds 1 and 2 are built of cluster anions [Nb6Cl12(CN)6]4- trans-coordinated by two Ca2+ complexes via CN ligands to form neutral macromolecular units [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] in 1 and [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] in 2. Water of coordination and cyanide ligands form hydrogen bonded 3D and 2D frameworks for 1 and 2, respectively. The structure of 3 consists of [Nb6Cl12(CN)6]4- cluster anions and [Ba(phen)2(H2O)]2+ complexes linked through bridging cyanide ligands to form a neutral three-dimensional framework in which each barium complex is bound to three neighboring Nb6 clusters and each Nb6 cluster is linked to six Ba complexes.     

Octadecanuclear cluster or 1D polymer with [[ML](2)Nb(CN)(8)](n) motifs as a function of [ML] (M = Ni(II), n = 6; M = Mn(II), n = infinity; L = macrocycle)

A nanosized octadecaheteronuclear aggregate, [[NiL(2)](12)[Nb(CN)(8)](6)(H(2)O)(6)], and a 1-D coordination polymer, [[MnL(1)](2)[Nb(CN)(8)](H(2)O)]( infinity ), have been obtained by self-assembly between the octacyanometalate [Nb(CN)(8)](4)(-) and [ML](2+) complexes. The dimensionality of the supramolecular architectures was found to be controlled by the [ML] module for which the equatorial coordination sites are blocked by a macrocyclic ligand. The crystal structures and magnetic properties for both the compounds are described.     

The role of carboxylate ligands in two novel cyanido-bridged 2D coordination networks Cu(II)-W(V) and Mn(II)-Nb(IV)

We report on the synthesis, molecular structure and magnetic properties of two novel coordination polymers: [{Cu(II)(4)(pic)(2)(H(2)O)(2)(MeOH)}{W(V)(CN)(8)}(2)]·MeOH·4H(2)O (1) and [{Mn(II)(3)(HCOO)(2)(H(2)O)(4)}{Mn(II)(H(2)O)(3)(HCONH(2))}(2){Nb(IV)(CN)(8)}(2)]·4HCONH(2)·2H(2)O (2). The single-crystal X-ray diffraction analysis of 1 shows that its molecular structure can be interpreted as a cyanido bridged (3,4,7)-connected 2D bilayer built of two different subnets sharing the tungsten centers. The magnetic measurements suggest that the system reveals long-range ferromagnetic ordering between Cu(II) and W(V) centers below 13.4 K. The molecular structure of (2) reveals a 2D topology of layers built of cyanido and formato bridging ligands. The system reveals ferrimagnetic behavior with a critical temperature at 17.8 K.     

High Tc ferrimagnetic organic-inorganic hybrid materials with MnII-L-MnII and MnII-NC-NbIV linkages (L=pyrazine, pyrazine-N,N'-dioxide, bipyrimidine)

A series of heterobimetallic, cyano-bridged 3D inorganic-organic hybrid networks with MnII-L-MnII and MnII-NC-NbIV linkages are reported. Reaction of [Mn(H2O)6]2+ with [Nb(CN)8]4- in the presence of organic linker L (pyrazine (pyz), pyrazine-N,N'-dioxide (pzdo), and 2,2'-bipyrimidine (bpym)) in H2O affords {MnII2(pz)2(H2O)4[NbIV(CN)8]}.pz.3H2O (1), {MnII2(pzdo)(H2O)4[NbIV(CN)8]}.5H2O (2), and {MnII2(bpym)(H2O)2[NbIV(CN)8]} (3), respectively. 1-3 were examined by X-ray crystallography and vibrational and magnetochemical studies. 1 is characterized by the coexistence of 3D inorganic cyano-bridged and 1D organic [Mn-(micro-pyz)]n2n+ sublattices along with the presence of monocoordinated and crystallization molecules of pyrazine. Assemblies 2 and 3 exhibit dimeric {MnII2-(micro-L)}4+ coordination motifs. The magnetic behavior of heterobimetallic 1-3 complexes is dominated by antiferromagnetic coupling between MnII and NbIV centers mediated by cyano bridges, resulting in long-range ferrimagnetic ordering with a high TC of 27 (1), 37 (2), and 50 K (3). The magneto-structural correlation leads to the conclusion that the magnitude of TC is related to the type of coordination polyhedra of [Nb(CN)8] moieties (SAPR (1), intermediate between SAPR and DD (2), and DD (3)), the relative number of cyano bridges per Mn2Nb unit, and coexistence of inorganic and organic connectivity. FC/ZFC responses appear to be sensitive to the degree of organic connectivity. The discussion of magneto-structural correlation is based on the spin-density properties of adequate heterobimetallic systems containing octacyanometalates.     

Mechanism of oxidation of benzaldehyde by polypyridyl oxo complexes of Ru(IV)

The oxidation of benzaldehyde and several of its derivatives to their carboxylic acids by cis-[Ru(IV)(bpy)2(py)(O)]2+ (Ru(IV)=O2+; bpy is 2,2'-bipyridine, py is pyridine), cis-[Ru(III)(bpy)2(py)(OH)]2+ (Ru(III)-OH2+), and [Ru(IV)(tpy)(bpy)(O)]2+ (tpy is 2,2':6',2'-terpyridine) in acetonitrile and water has been investigated using a variety of techniques. Several lines of evidence support a one-electron hydrogen-atom transfer (HAT) mechanism for the redox step in the oxidation of benzaldehyde. They include (i) moderate k(C-H)/k(C-D) kinetic isotope effects of 8.1 +/- 0.3 in CH3CN, 9.4 +/- 0.4 in H2O, and 7.2 +/- 0.8 in D2O; (ii) a low k(H2O/D2O) kinetic isotope effect of 1.2 +/- 0.1; (iii) a decrease in rate constant by a factor of only approximately 5 in CH3CN and approximately 8 in H2O for the oxidation of benzaldehyde by cis-[Ru(III)(bpy)2(py)(OH)]2+ compared to cis-[Ru(IV)(bpy)2(py)(O)]2+; (iv) the appearance of cis-[Ru(III)(bpy)2(py)(OH)]2+ rather than cis-[Ru(II)(bpy)2(py)(OH2)]2+ as the initial product; and (v) the small rho value of -0.65 +/- 0.03 in a Hammett plot of log k vs sigma in the oxidation of a series of aldehydes. A mechanism is proposed for the process occurring in the absence of O2 involving (i) preassociation of the reactants, (ii) H-atom transfer to Ru(IV)=O2+ to give Ru(III)-OH2+ and PhCO, (iii) capture of PhCO by Ru(III)-OH2+ to give Ru(II)-OC(O)Ph+ and H+, and (iv) solvolysis to give cis-[Ru(II)(bpy)2(py)(NCCH3)]2+ or the aqua complex and the carboxylic acid as products.     

Crystal structures and magnetic properties of two low-dimensional materials constructed from [Mn(III)(salen)H2O]+ and [M(CN)8](3-/4-) (M = Mo or W) precursors

The syntheses, X-ray structures, and magnetic behaviors of two new cyano-bridged assemblies, the molecular [Mn(III)(salen)H2O]3[W(V)(CN)8].H2O (1) and one-dimensional [Mn(salen)(H2O)2]2[[Mn(salen)(H2O)][Mn(salen)]2[Mo(CN)(8)]].0.5ClO4.0.5OH.4.5H2O (2), are presented. Compound 1 crystallizes in the monoclinic system, has space group P2(1)/c, and has unit cell constants a = 13.7210(2) A, b = 20.6840(4) A, c = 20.6370(2) A, and Z = 4. Compound 2 crystallizes in the triclinic system, has space group P, and has unit cell dimensions a = 18.428(4) A, b = 18.521(3) A, c = 18.567(4) A, and Z = 2. The structure of 1 consists of the asymmetric V-shaped Mn-NC-W-NC-Mn-O(phenolate)-Mn molecules, where W(V) coordinates with [Mn(salen)H2O] and singly phenolate-bridged [Mn(salen)H2O]2 moieties through the neighboring cyano bridges. The [W(V)(CN)8]3- ion displays distorted square-antiprism geometry. The structure of 2 consists of the cyano-bridged [Mn3(III)Mo(IV)]n- repeating units linked by double phenolate bridges into one-dimensional zigzag chains. The Mn(III) centers are bound to Mo(IV) of square-antiprism geometry through the neighboring cyano bridges. The magnetic studies of 1 reveal the antiferromagnetic intramolecular interactions through the CN and phenolate bridges and the relatively weak intermolecular interactions. Compound 1 becomes antiferromagnetically ordered below TN = 4.6 K. The presence of the magnetic anisotropy is documented with the MH measurements carried out for both polycrystalline and single-crystal samples. At T = 1.9 K, the spin-flop transition is observed in the field of 18 kOe applied parallel to the bc plane, which is the easy plane of magnetization. Field dependence of magnetization of 1 shows field-induced metamagnetic behavior from the antiferromagnetic ground state of ST = 3/2 to the state of ST = 5/2. The magnetic properties of 2 indicate a weak antiferromagnetic interaction between Mn(III) centers in double-phenolate-bridged [Mn(III)(salen)]2 dinuclear subunits and a very weak ferromagnetic interaction between them through the diamagnetic [Mo(IV)(CN)8]4- spacer.     

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.     

High-nuclearity metal-cyanide clusters: synthesis,magnetic properties,and inclusion behavior of open-cage species incorporating [(tach)M(CN)3] (M = Cr,Fe, Co) complexes

The use of 1,3,5-triaminocyclohexane (tach) as a capping ligand in generating metal-cyanide cage clusters with accessible cavities is demonstrated. The precursor complexes [(tach)M(CN)(3)] (M = Cr, Fe, Co) are synthesized by methods similar to those employed in preparing the analogous 1,4,7-triazacyclononane (tacn) complexes. Along with [(tach)Fe(CN)(3)](1)(-), the latter two species are found to adopt low-spin electron configurations. Assembly reactions between [(tach)M(CN)(3)] (M = Fe, Co) and [M'(H(2)O)(6)](2+) (M' = Ni, Co) in aqueous solution afford the clusters [(tach)(4)(H(2)O)(12)Ni(4)Co(4)(CN)(12)](8+), [(tach)(4)(H(2)O)(12)Co(8)(CN)(12)](8+), and [(tach)(4)(H(2)O)(12)Ni(4)Fe(4)(CN)(12)](8+), each possessing a cubic arrangement of eight metal ions linked through edge-spanning cyanide bridges. This geometry is stabilized by hydrogen-bonding interactions between tach and water ligands through an intervening solvate water molecule or bromide counteranion. The magnetic behavior of the Ni(4)Fe(4) cluster indicates weak ferromagnetic coupling (J = 5.5 cm(-)(1)) between the Ni(II) and Fe(III) centers, leading to an S = 6 ground state. Solutions containing [(tach)Fe(CN)(3)] and a large excess of [Ni(H(2)O)(6)](2+) instead yield a trigonal pyramidal [(tach)(H(2)O)(15)Ni(3)Fe(CN)(3)](6+) cluster, in which even weaker ferromagnetic coupling (J = 1.2 cm(-)(1)) gives rise to an S = (7)/(2) ground state. Paralleling reactions previously performed with [(Me(3)tacn)Cr(CN)(3)], [(tach)Cr(CN)(3)] reacts with [Ni(H(2)O)(6)](2+) in aqueous solution to produce [(tach)(8)Cr(8)Ni(6)(CN)(24)](12+), featuring a structure based on a cube of Cr(III) ions with each face centered by a square planar [Ni(CN)(4)](2)(-) unit. The metal-cyanide cage differs somewhat from that of the analogous Me(3)tacn-ligated cluster, however, in that it is distorted via compression along a body diagonal of the cube. Additionally, the compact tach capping ligands do not hinder access to the sizable interior cavity of the molecule, permitting host-guest chemistry. Mass spectrometry experiments indicate a 1:1 association of the intact cluster with tetrahydrofuran (THF) in aqueous solution, and a crystal structure shows the THF molecule to be suspended in the middle of the cluster cavity. Addition of THF to an aqueous solution containing [(tach)Co(CN)(3)] and [Cu(H(2)O)(6)](2+) templates the formation of a closely related cluster, [(tach)(8)(H(2)O)(6)Cu(6)Co(8)(CN)(24) superset THF](12+), in which paramagnetic Cu(II) ions with square pyramidal coordination are situated on the face-centering sites. Reactions intended to produce the cubic [(tach)(4)(H(2)O)(12)Co(8)(CN)(12)](8+) cluster frequently led to an isomeric two-dimensional framework, [(tach)(H(2)O)(3)Co(2)(CN)(3)](2+), exhibiting mer rather than fac stereochemistry at the [Co(H(2)O)(3)](2+) subunits. Attempts to assemble larger edge-bridged cubic clusters by reacting [(tach)Cr(CN)(3)] with [Ni(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) complexes instead generated extended one- or two-dimensional solids. The magnetic properties of one of these solids, two-dimensional [(tach)(2)(cyclam)(3)Ni(3)Cr(2)(CN)(6)]I(2), suggest metamagnetic behavior, with ferromagnetic intralayer coupling and weak antiferromagnetic interactions between layers.     

Near-infrared luminescent and magnetic cyano-bridged coordination polymers Nd(phen)n(DMF)m[M(CN)8] (M = Mo, W)

New cyano-bridged coordination polymers [Nd(phen)(2)(DMF)(2)(H(2)O)Mo(CN)(8)]·2H(2)O (1) and [Nd(phen)(DMF)(5)M(CN)(8)]·xH(2)O [M = Mo (2), W (3); phen = 1,10-phenanthroline] have one-dimensional structures with variable number of phenanthroline ligands. Compounds exhibit photoluminescence in the near-infrared region and ferromagnetic Nd(3+)-M(5+) interactions.     

Rare tetranuclear mixed-valent [Mn(II)2Mn(IV)2] clusters as building blocks for extended networks

We report the synthesis of a series of mixed valence Mn(II/IV) tetranuclear clusters [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(EtOH)(6)Br(2)]Br(2) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)Cl(4)].2EtOH.H(2)O (.2EtOH.H(2)O), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(heedH(2))(2)](ClO(4))(4) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(MeCN)(2)(H(2)O)(2)(bpy)(2)](ClO(4))(4) () and [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(bpy)(2)Br(4)].2MeOH (.2MeOH). Clusters are constructed from the tripodal ligand N,N-bis(2-hydroxyethyl)ethylene diamine (heedH(2)) and represent rare examples of tetranuclear Mn clusters possessing the linear trans zig-zag topology, being the first Mn(II/IV) mixed-valent clusters of this type. The molecular clusters can then be used as building blocks in tandem with the (linear) linker dicyanamide ([N(CN)(2)](-), dca(-)) for the formation of a novel extended network {[Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)(MeOH)(2)(dca)(2)]Br(2)}(n) (), which exhibits a rare form of the 2D herring bone topology.     

Analysis of the photomagnetic properties of cyano-bridged heterobimetallic complexes by X-ray diffraction

Single crystal synchrotron X-ray diffraction measurements have been carried out on [Nd(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O (DMF = dimethyl-formamide), 1; [Y(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 2; [Ce(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 3; [Sm(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 4; [Tb(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 5; [Yb(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 6; and [Nd(DMF)(4)(H(2)O)(3)(μ-CN)Co(CN)(5)]·H(2)O, 7, at 15(2) K with and without UV illumination of the crystals. Significant changes in unit cell parameters are observed for all of the iron-containing complexes, while compound 7 shows no response to UV illumination. These results are consistent with previous results and are furthermore reproduced by powder synchrotron X-ray diffraction for compounds 1 and 7. Photoexcited crystal structures have been determined for 1-6 from refinements of two-conformer models, and excited state occupancies in the range 80-94% are found. Significant bond length changes are observed for the Fe-ligand bonds (up to 0.06 ?), the cyano bonds (up to 0.02 ?), and the lanthanide-ligand bonds (up to 0.1 ?). On the contrary, powder X-ray diffraction on the simple compound K(3)Fe(CN)(6), 8, upon UV illumination does not show any structural changes, suggesting that the photomagnetic effect requires the presence of both the transition metal and the lanthanide ion. Photomagnetic measurements show an increase in magnetization of the excited state of 1 of up to 3%, which is much diminished compared with previously published values of 45%. Furthermore, they show that the isostructural complex [La(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 9, exhibits identical magnetic responses in the UV-induced excited crystal structure.     

Synthesis and structural characterization of bi- and trimetallic octacyanometalate(IV) complexes: [Delta,Lambda-MII(en)3][cis-MII(en)2(OH2)][MIV(CN)8].2H2O and [cis-MII(en)2(OH2)]2[(mu-NC)2MIV(CN)6].4H2O (MII = Mn, Co, Ni; MIV = Mo, W)

Treatment of [M(II)(en)(3)][OTs](2) or methanolic ethylenediamine solutions containing transition metal p-toluenesulfonates (M(II) = Mn, Co) with aqueous K(4)M(IV)(CN)(8).2H(2)O or Cs(3)M(V)(CN)(8) (M(IV) = Mo, W; M(V) = Mo) affords crystalline clusters of [M(II)(en)(3)][cis-M(II)(en)(2)(OH(2))(mu-NC)M(IV)(CN)(7)].2H(2)O (M(IV) = Mo; M(II) = Mn, 1; Ni, 5; M(IV) = W; M(II) = Mn, 2; Ni, 6) and [cis-M(II)(en)(2)(OH(2))](2)[(mu-NC)(2)M(IV)(CN)(6)].4H(2)O (M(IV) = Mo; M(II) = Co, 3; Ni, 7; M(IV) = W; M(II) = Co, 4) stoichiometry. Each cluster contains cis-M(II)(en)(2)(OH(2))(mu-NC)(2+) units that likely result from dissociative loss of en from [M(II)(en)(3)](2+), affording cis-M(II)(en)(2)(OH(2))(2)(2+) intermediates that are trapped by M(IV)(CN)(8)(4-).     

Expanded Prussian blue analogues incorporating [Re6Se8(CN)6](3-/4-) clusters: adjusting porosity via charge balance

Face-capped octahedral [Re(6)Se(8)(CN)(6)](3-/4-) clusters are used in place of octahedral [M(CN)(6)](3-/4-) complexes for the synthesis of microporous Prussian blue type solids with adjustable porosity. The reaction between [Fe(H(2)O)(6)](3+) and [Re(6)Se(8)(CN)(6)](4-) in aqueous solution yields, upon heating, Fe(4)[Re(6)Se(8)(CN)(6)](3).36H(2)O (4). A single-crystal X-ray analysis confirms the structure of 4 to be a direct expansion of Prussian blue (Fe(4)[Fe(CN)(6)](3).14H(2)O), with [Re(6)Se(8)(CN)(6)](4-) clusters connected through octahedral Fe(3+) ions in a cubic three-dimensional framework. As in Prussian blue, one out of every four hexacyanide units is missing from the structure, creating sizable, water-filled cavities within the neutral framework. Oxidation of (Bu(4)N)(4)[Re(6)Se(8)(CN)(6)] (1) with iodine in methanol produces (Bu(4)N)(3)[Re(6)Se(8)(CN)(6)] (2), which is then metathesized to give the water-soluble salt Na(3)[Re(6)Se(8)(CN)(6)] (3). Reaction of [Co(H(2)O)(6)](2+) or [Ni(H(2)O)(6)](2+) with 3 in aqueous solution affords Co(3)[Re(6)Se(8)(CN)(6)](2).25H(2)O (5) or Ni(3)[Re(6)Se(8)(CN)(6)](2).33H(2)O (6). Powder X-ray diffraction data show these compounds to adopt structures based on the same cubic framework present in 4, but with one out of every three cluster hexacyanide units missing as a consequence of charge balance. In contrast, reaction of [Ga(H(2)O)(6)](3+) with 3 gives Ga[Re(6)Se(8)(CN)(6)].6H(2)O (7), wherein charge balance dictates a fully occupied cubic framework enclosing much smaller cavities. The expanded Prussian blue analogues 4-7 can be fully dehydrated, and retain their crystallinity with extended heating at 250 degrees C. Consistent with the trend in the frequency of framework vacancies, dinitrogen sorption isotherms show porosity to increase along the series of representative compounds 7, Ga(4)[Re(6)Se(8)(CN)(6)](3).38H(2)O, and 6. Furthermore, all of these phases display a significantly higher sorption capacity and surface area than observed in dehydrated Prussian blue. Despite incorporating paramagnetic [Re(6)Se(8)(CN)(6)](3-) clusters, no evidence for magnetic ordering in compound 6 is apparent at temperatures down to 5 K. Reactions related to those employed in preparing compounds 4-6, but carried out at lower pH, produce the isostructural phases H[cis-M(H(2)O)(2)][Re(6)Se(8)(CN)(6)].2H(2)O (M = Fe (8), Co (9), Ni (10)). The crystal structure of 8 reveals a densely packed three-dimensional framework in which [Re(6)Se(8)(CN)(6)](4-) clusters are interlinked through a combination of protons and Fe(3+) ions.     

Encapsulation of cyanometalates by a tris-macrocyclic ligand tricopper(II) complex: syntheses, structural variation, and magnetic exchange coupling pathways

The reaction of [M(CN)(6)](3-) (M = Cr(3+), Mn(3+), Fe(3+), Co(3+)) and [M(CN)(8)](4-/3-) (M = Mo(4+/5+), W(4+/5+)) with the trinuclear copper(II) complex of 1,3,5-triazine-2,4,6-triyltris[3-(1,3,5,8,12-pentaazacyclotetradecane)] ([Cu(3)(L)](6+)) leads to partially encapsulated cyanometalates. With hexacyanometalate(III) complexes, [Cu(3)(L)](6+) forms the isostructural host-guest complexes [[[Cu(3)(L)(OH(2))(2)][M(CN)(6)](2)][M(CN)(6)]][M(CN)(6)]30 H(2)O with one bridging, two partially encapsulated, and one isolated [M(CN)(6)](3-) unit. The octacyanometalates of Mo(4+/5+) and W(4+/5+) are encapsulated by two tris-macrocyclic host units. Due to the stability of the +IV oxidation state of Mo and W, only assemblies with [M(CN)(8)](4-) were obtained. The Mo(4+) and W(4+) complexes were crystallized in two different structural forms: [[Cu(3)(L)(OH(2))](2)[Mo(CN)(8)]](NO(3))(8)15 H(2)O with a structural motif that involves isolated spherical [[Cu(3)(L)(OH(2))](2)[M(CN)(8)]](8+) ions and a "string-of-pearls" type of structure [[[Cu(3)(L)](2)[M(CN)(8)]][M(CN)(8)]](NO(3))(4) 20 H(2)O, with [M(CN)(8)](4-) ions that bridge the encapsulated octacyanometalates in a two-dimensional network. The magnetic exchange coupling between the various paramagnetic centers is characterized by temperature-dependent magnetic susceptibility and field-dependent magnetization data. Exchange between the CuCu pairs in the [Cu(3)(L)](6+) "ligand" is weakly antiferromagnetic. Ferromagnetic interactions are observed in the cyanometalate assemblies with Cr(3+), exchange coupling of Mn(3+) and Fe(3+) is very small, and the octacoordinate Mo(4+) and W(4+) systems have a closed-shell ground state.     

2-Aminoisobutyric acid in Co(II) and Co(II)/Ln(III) chemistry: homometallic and heterometallic clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co(II)(4)(aib)(3)(aibH)(3)(NO(3))](NO(3))(4)·2.8CH(3)OH·0.2H(2)O (1·2.8CH(3)OH·0.2H(2)O), {Na(2)[Co(II)(2)(aib)(2)(N(3))(4)(CH(3)OH)(4)]}(n) (2), [Co(II)(6)La(III)(aib)(6)(OH)(3)(NO(3))(2)(H(2)O)(4)(CH(3)CN)(2)]·0.5[La(NO(3))(6)]·0.75(ClO(4))·1.75(NO(3))·3.2CH(3)CN·5.9H(2)O (3·3.2CH(3)CN·5.9H(2)O), [Co(II)(6)Pr(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Pr(NO(3))(5)]·0.41[Pr(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.59[Co(NO(3))(3)(H(2)O)]·0.2(ClO(4))·0.25H(2)O (4·0.25H(2)O), [Co(II)(6)Nd(III)(aib)(6)(OH)(3)(NO(3))(2.8)(CH(3)OH)(4.7)(H(2)O)(1.5)]·2.7(ClO(4))·0.5(NO(3))·2.26CH(3)OH·0.24H(2)O (5·2.26CH(3)OH·0.24H(2)O), [Co(II)(6)Sm(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Sm(NO(3))(5)]·0.44[Sm(NO(3))(3)(ClO(4))(0.5)(H(2)O)(1.5)]·0.56[Co(NO(3))(3)(H(2)O)]·0.22(ClO(4))·0.3H(2)O (6·0.3H(2)O), [Co(II)(6)Eu(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)OH)(4.87)(H(2)O)(1.13)](ClO(4))(2.5)(NO(3))(0.5)·2.43CH(3)OH·0.92H(2)O (7·2.43CH(3)OH·0.92H(2)O), [Co(II)(6)Gd(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.9)(H(2)O)(1.2)]·2.6(ClO(4))·0.5(NO(3))·2.58CH(3)OH·0.47H(2)O (8·2.58CH(3)OH·0.47H(2)O), [Co(II)(6)Tb(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·[Tb(NO(3))(5)]·0.034[Tb(NO(3))(3)(ClO(4))(0.5)(H(2)O)(0.5)]·0.656[Co(NO(3))(3)(H(2)O)]·0.343(ClO(4))·0.3H(2)O (9·0.3H(2)O), [Co(II)(6)Dy(III)(aib)(6)(OH)(3)(NO(3))(2.9)(CH(3)OH)(4.92)(H(2)O)(1.18)](ClO(4))(2.6)(NO(3))(0.5)·2.5CH(3)OH·0.5H(2)O (10·2.5CH(3)OH·0.5H(2)O), [Co(II)(6)Ho(III)(aib)(6)(OH)(3)(NO(3))(3)(CH(3)CN)(6)]·0.27[Ho(NO(3))(3)(ClO(4))(0.35)(H(2)O)(0.15)]·0.656[Co(NO(3))(3)(H(2)O)]·0.171(ClO(4)) (11), [Co(II)(6)Er(III)(aib)(6)(OH)(4)(NO(3))(2)(CH(3)CN)(2.5)(H(2)O)(3.5)](ClO(4))(3)·CH(3)CN·0.75H(2)O (12·CH(3)CN·0.75H(2)O), and [Co(II)(6)Tm(III)(aib)(6)(OH)(3)(NO(3))(3)(H(2)O)(6)]·1.48(ClO(4))·1.52(NO(3))·3H(2)O (13·3H(2)O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3-13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co(II)(6)] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2-300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.     

On, off and intermediate coordination of a bridgehead triarylamine donor in tripodal complexes: towards the tuning of coordinative bond distance

A series of first row transition metal complexes of the tripodal ligand 2,2',2"-nitrilotribenzoic acid H3L has been prepared and characterised by X-ray crystallography: Mononuclear [M(L)]- species [Cu(H2O)4]3[Cu(L)(H2O)]6.25H2O (2), [Co(H2O)6][Co(L)(H2O)].8H2O (4), [Zn(H2O)6][Zn(L)(H2O)].8H2O (5) and a neutral [M(L)] complex [Fe(III)2(L)(H2O)3].5H2O (8) are formed as well as dimeric [M(L)]2 2- species (HNEt3)2[Cu(L)]2.2CH3CN (1), (HNEt3)3[Ni(L)]2(ClO4).H2O (3), (HNEt3)2[Fe(II)(L)]2.2CH3CN (6) and (HNEt3)2[Fe(III)2(L)2(mu-O)](7). The complexes display a unique variation in the M-N distance (2.09 A for Cu(II) to 3.29 A for Fe(III)) to the bridgehead triphenylamine donor and are classified into compounds with "On","Off" and "Intermediate" N-coordination. The trigonal-bipyramidal coordination polyhedron changes towards tetrahedral in the intermediate and octahedral in the Off-state. The M-N distance of individual complexes is reversibly tuned by external chemical input such as changes of metal ion oxidation state (Fe(II)/Fe(III)) or variation of the axial coligand as a consequence of solvent or pH variation. Possible reasons for the exceptional tolerance of the M-N bond to distance variations are discussed under consideration of gas phase DFT calculations of [Zn(L)]-.     

Synthesis and reactivity of niobium complexes having a tripodal triaryloxide ligand in bidentate, tridentate, and tetradentate coordination modes

The synthesis and reactivity of niobium complexes incorporating a tripodal triphenol (tris(3,5-tert-butyl-2-hydroxylphenyl)methane = H(3)[O(3)]) have been investigated. Addition of one equivalent of NbCl(5) in CH(3)CN to H(3)[O(3)] in toluene led to partial HCl elimination, giving [H(O(3))]NbCl(3)(CH(3)CN) (1) with a bidendtate bis(aryloxide) ligand and a pendant phenol arm. Treatment of 1 with THF afforded [H(O(3))]NbCl(3)(THF) (2). Deprotonation of 1 with NEt(3) in toluene promoted coordination of the pendant phenol group to generate (Et(3)NH)[(syn-O(3))NbCl(3)] (3-syn). Prolonged heating of 3-syn resulted in clean conversion to the anti isomer (3-anti). Attempted deprotonation of 2 with PhCH(2)MgCl provided [H(O(3))]Nb(CH(2)Ph)(3) (4), in which alkylation took place at the metal center but the pendant phenol arm remained intact. When 3-syn was treated with PhCH(2)MgCl, [O(3)C]Nb(CH(2)Ph) (5) was produced via C-H activation of the methine C-H bond. The analogous reaction with 3-anti provided a benzylidene complex [anti-O(3)]Nb(CHPh)(THF) (6). During the course of the reaction, the anti ligand conformation is retained. Upon heating, 4 underwent methine C-H and phenol O-H activation, yielding the metalatrane 5. Complexes 1, 3-syn, 3-anti, 4, and 5 were characterized by X-ray diffraction.     

Chiral osmium complexes with sterically bulky Schiff-base ligands. Crystal structures of Os(IV) derivatives and the reactivity and catalytic cyclopropanation of alkenes with EDA

The syntheses and reactivities of sterically encumbered trans-dioxoosmium(VI) complexes containing Schiff-base ligands bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamine (H2tBu-salch) and bis(3,5-dibromosalicylidene)-1,2-cyclohexane-diamine (H2Br-salch) are described. Reactions of [Os(VI)tBu-salch)O2] (1a) and [Os(VI)(Br-salch)O2] (1b) with PPh(3), p-X-arylamines (X = NO2, CN), N2H4 x H2O, Ph2NNH2, SOCl2, CF3CO2H, Br2, and I2 under reducing conditions gave [Os(II)(Br-salch)(OPPh3)2] (2), [Os(IV)(Br-salch)(p-X-C6H4NH)2] (3), [mu-O-{Os(IV)(tBu-salch)(p-NO2C6H4NH)}2] (4), [Os(II)(Br-salch)(N2)(H2O)] (5), [Os(IV)(tBu-salch)(OH)(Cl)] (6), [Os(IV)(tBu-salch)(OH)2] (7), [Os(IV)(tBu-salch)Cl2] (8), [Os(IV)(tBu-salch)(CF3CO2)2] (9), [Os(IV)(tBu-salch)Br2] (10), and [Os(IV)(tBu-salch)I2] (11), respectively. X-ray crystal structure determinations of [Os(IV)(Br-salch)(p-NO2C6H4NH)2] (3a), [Os(IV)(Br-salch)(p-CNC6H4NH)2] (3b), 6, 8, 9, and 11 reveal the Os-N(amido) distances to be 1.965(4)-1.995(1) A for the bis(amido) complexes, Os-Cl distances of 2.333(8)-2.3495(1) A for 6 and 8, Os-O(CF3CO2) distances of 2.025(6)-2.041(6) A for 9, and Os-I distances of 2.6884(6)-2.6970(6) A for 11. Upon UV irradiation, (1S,2S)-(1a) reacted with aryl-substituted alkenes to give the corresponding epoxides in moderate yields, albeit with no enantioselectivity. The (1R,2R)-6 catalyzed cyclopropanation of a series of substituted styrenes exhibited moderate to good enantioselectivity (up to 79% ee) and moderate trans selectivity.