Trans Water Molecules Research Articles

Catena-Poly[[di-aqua-bis-(1,3-di-hydro-3-oxo-isobenzo-furan-1-acetato)-copper(II)]-μ-N,N'-(ethane-1,2-di-yl)dinicotinamide

The title compound, {[Cu(C10H7O4)2(C14H14N4O2)(H2O)2]n, contains octa-hed-rally coordinated CuII ions ligated by two bis-(1,3-di-hydro-3-oxo-1-isobenzo-furan-acetate (dibf) ligands and two trans water mol-ecules, linked by N,N'-(ethane-1,2-di-yl)dinicotinamide (edn) ligands into mono-periodic coordination polymer chains. The dibf ligands exhibit a pseudo-mirror positional disorder over two positions in a 89.2 (3)/10.8 (3) ratio; the central amide groups of the edn ligands are disordered pseudo-rotationally in the same ratio. These mono-periodic chain motifs are held into supra-molecular di-periodic supra-molecular layers by means of N-H⋯O hydrogen bonding between edn amide groups and unligated dibf carboxyl-ate O atoms. In turn, the supra-molecular layers are held by crystal packing forces into the full crystal structure of the title compound.

Co (II) Complexes Based on the Bis-Pyrazol-S-Triazine Pincer Ligand: Synthesis, X-ray Structure Studies, and Cytotoxic Evaluation

Four pincer-type Co (II) complexes of the 2,4-bis (3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine ligand (L) were evaluated for their cytotoxic activities against lung and breast cancer cell lines using cell viability assay. The X-ray single crystal structure of [Co(L)(H2O)2Br]Br (1) confirmed the pincer coordination behavior of the ligand L as an N-tridentate chelate. The hexa-coordination environment of Co (II) is completed by one bromide ion completing the equatorial plane of the octahedral structure and two trans water molecules at the axial positions. It crystallized in the monoclinic crystal system and P21/m space group with crystal parameters of a = 11.3170(10) Å, b = 7.4613(7) Å, c = 12.6917(12) Å and β = 95.927(3)°. Based on Hirshfeld analysis, the most dominant contacts are H…H (48.8%), Br…H (17.6%), H…C (11.2%) and O…H (10.1%), where the Br…H interactions are the most significant. The cytotoxic evaluation of the studied systems indicated that complex [Co(L)(NO3)2] (4) has the highest activity against lung (A-549) and breast (MCF-7) cell lines. In contrast, complex [Co(L)(H2O)3](ClO4)2.H2O(3) has the lowest cytotoxic activity against both cell lines.

Facile Conversion of syn-[FeIV (O)(TMC)]2+ into the anti Isomer via Meunier's Oxo-Hydroxo Tautomerism Mechanism.

The syn and anti isomers of [FeIV(O)(TMC)]2+ (TMC=tetramethylcyclam) represent the first isolated pair of synthetic non‐heme oxoiron(IV) complexes with identical ligand topology, differing only in the position of the oxo unit bound to the iron center. Both isomers have previously been characterized. Reported here is that the syn isomer [FeIV(Osyn)(TMC)(NCMe)]2+ (2) converts into its anti form [FeIV(Oanti)(TMC)(NCMe)]2+ (1) in MeCN, an isomerization facilitated by water and monitored most readily by 1H NMR and Raman spectroscopy. Indeed, when H2 18O is introduced to 2, the nascent 1 becomes 18O‐labeled. These results provide compelling evidence for a mechanism involving direct binding of a water molecule trans to the oxo atom in 2 with subsequent oxo–hydroxo tautomerism for its incorporation as the oxo atom of 1. The nonplanar nature of the TMC supporting ligand makes this isomerization an irreversible transformation, unlike for their planar heme counterparts.

Facile Conversion of syn‐[FeIV(O)(TMC)]2+ into the anti Isomer via Meunier's Oxo–Hydroxo Tautomerism Mechanism

AbstractThe syn and anti isomers of [FeIV(O)(TMC)]2+ (TMC=tetramethylcyclam) represent the first isolated pair of synthetic non‐heme oxoiron(IV) complexes with identical ligand topology, differing only in the position of the oxo unit bound to the iron center. Both isomers have previously been characterized. Reported here is that the syn isomer [FeIV(Osyn)(TMC)(NCMe)]2+ (2) converts into its anti form [FeIV(Oanti)(TMC)(NCMe)]2+ (1) in MeCN, an isomerization facilitated by water and monitored most readily by 1H NMR and Raman spectroscopy. Indeed, when H218O is introduced to 2, the nascent 1 becomes 18O‐labeled. These results provide compelling evidence for a mechanism involving direct binding of a water molecule trans to the oxo atom in 2 with subsequent oxo–hydroxo tautomerism for its incorporation as the oxo atom of 1. The nonplanar nature of the TMC supporting ligand makes this isomerization an irreversible transformation, unlike for their planar heme counterparts.

The pKa value of the proximal water molecule trans to a high-valent MnV[double bond, length as m-dash]O porphyrin: towards the control of reactivity by pH.

The high-valent manganese-oxo species of Mn-TMPyP4 porphyrin interacts in the minor grooves of AT-rich regions of DNA and mediates hydroxylation of C-H bonds of deoxyribose leading to DNA break. The reaction was observed at different pHs. It is shown that the hydroxylation was not efficient at low pH (pH 6) while it worked well at higher pH (pH 8). Deprotonation of the coordinated water molecule, trans to the manganese-oxo entity, into a hydroxide anion drives high-valent manganese-oxo porphyrin toward hydroxylation at pH > 7.

A Spin Crossover Transition in a Mn(II) Chain Compound

Three new compounds have been synthesized and characterized with Fe(II), Co(II) and Mn(II), the polynitrile anionic ligand 1,1,3,3-tetracyano-2-(3-hydroxypropoxy)-propenide (tcnopr3OH−) and the co-ligand 4,4′-bipyridine (4,4′-bpy). The Fe(II) compound, formulated as [FeII(tcnoprOH)2(H2O)2(4,4′-bpy)2] (1), contains monomeric complexes where the Fe(II) ion is coordinated to two trans polynitrile ligands, two trans 4,4′-bpy ligands and two trans water molecules. Compounds [MII(H2O)4(µ-4,4′-bpy)][MII(tcnoprOH)4(µ-4,4′-bpy)].3H2O, M = Mn (2) and Co (3), are isostructural and crystallize in segregated cationic and anionic chains that can be formulated as [MII(H2O)4(µ-4,4′-bpy)]n2n+ and [MII(tcnoprOH)4(µ-4,4′-bpy)]n2n−, respectively with M = Mn (2) and Co (3). The magnetic properties of Compound 1 show the expected paramagnetic behavior for an isolated high spin S = 2 Fe(II) ion with a zero field splitting of |D| = 4.0(1) cm−1. Compound 3 presents the expected behavior for isolated Co(II) centers, whereas Compound 2 shows an unexpected partial smooth spin crossover (SCO) transition in the anionic [MnII(tcnoprOH)4(µ-4,4′-bpy)]n2n− chain together with a paramagnetic contribution of the cationic [MnII(H2O)4(µ-4,4′-bpy)]n2n+ chain. This behavior has been confirmed with DSC measurements. This is one of the very few examples of SCO transition observed in a Mn(II) complex and the first one in a Mn(II) chain.

Evidence of Unusually Long Metal–Aqua Interaction: The Crystal Structure of Tetraphenylphosponium Rhenium(V)aquatetracyanonitrido Monohydrate Tri-terpyridine

The rhenium(V)aquatetracyanonitrido complex with 2,2′,2″-terpyridine (trpy) as adduct has been isolated and characterized with IR and X-ray crystallography. The title compound crystallizes in the monoclinic space group P21/n with unit cell parameters: a = 16.6829(2), b = 25.7198(10), c = 19.7098(3)A, β = 94.3860(10)°, V = 8432.3(2) A3, Z = 4. The rhenium in the anion has a distorted octahedral geometry with the Re(V) atom surrounded by the terminal nitrido ligand, four carbon atoms of the cyanide ligands and water molecule trans (171.33(4)°) to the nitride group. The water molecule is situated between the rhenium atom and one of the trpy nitrogen ligands with an exceptionally long metal aqua interaction equal to 2.658(3)A and with a distance equal to 2.804(5)A between the oxygen atom and the trpy nitrogen atom. Principal dimensions for this compound are; Re ≡ N = 1.655(3), Re-C1 = 2.100(4), Re-C2 = 2.094(5), Re-C3 = 2.094(4), Re-C4 = 2.113(4)A. The water molecule is situated between the rhenium atom and one of the trpy nitrogen ligands with an exceptionally long metal aqua interaction equal to 2.658(3)A and with a distance equal to 2.804(5)A between the aqua group and the nitrogen atom.

Li+ and Ca2+ Derivatives of the Isonicotinate-N-oxide Ion Including Single Crystal-to-Single Crystal Transformations

Crystals of [Li(inox)(H2O)] (where inox– = the isonicotinate-N-oxide ion) are obtained from aqueous solution. The Li+ cations and the carboxylate anions form a two-dimensional (2D) sheet containing four-membered (−Li–O–Li–O−) rings and 16-membered (−Li–O–C–O−)4 rings; the sheets are linked to adjacent parallel sheets through hydrogen bonds. Crystals of solvent-free [Li(inox)], obtained from t-butanol, consist of a three-dimensional network which can also be prepared in microcrystalline form by dehydration of [Li(inox)(H2O)] at 200 °C. Crystals of [Ca(inox)2(H2O)2] contain 2D sheets with 4,4 topology in which Ca2+ ions, bound by trans water molecules, provide the 4-connecting nodes. The Ca(H2O)22+ units are linked by carboxylate groups to generate 16-membered (−Ca–O–C–O−)4 rings. Sheets are bound together by hydrogen bonds between the pyridine-N-oxide units and coordinated water molecules. [Ca(inox)2(H2O)2] can be dehydrated at 190 °C in a single crystal-to-single crystal transformation to give [Ca(inox)2] whose structure is related to that of the hydrated precursor. A proposed solid-state mechanism for this single crystal-to-single crystal transformation, in which the N-oxide takes up the site on calcium vacated by water is proposed.

Synthesis, crystal structure, and magnetic characterization of the three-dimensional compound [Co2(cbut)(H2O)3]n (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid).

A novel cobalt(II) complex of formula [Co2(cbut)(H2O)3]n (1) (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid) has been synthesized under hydrothermal conditions and its crystal structure has been determined by means of synchrotron radiation and neutron powder diffraction. The crystal structure of 1 consists of layers of cobalt(II) ions extending in the bc-plane which are pillared along the crystallographic a-axis through the skeleton of the cbut(4-) ligand. Three crystallographically independent cobalt(II) ions [Co(1), Co(2), and Co(3)] occur in 1. They are all six-coordinate with four carboxylate-oxygens [Co(1)-Co(3)] and two cis-[Co(1)] or trans-water molecules [Co(2) and Co(3)] building distorted octahedral surroundings. Regular alternating double oxo(carboxylate) [between Co(1) and Co(1a)] and oxo(carboxylate) plus one aqua and a syn-syn carboxylate bridges [between Co(1) and Co(2)] occur along the crystallographic b-axis, the values of the cobalt-cobalt separation being 3.1259(8) and 3.1555(6) Å, respectively. These chains are connected to the Co(3) atoms through the OCO carboxylate along the [011] direction leading to the organic-inorganic bc-layers with Co(1)-OCO(anti-syn)-Co(3) and Co(2)-OCO(anti-anti)-Co(3) distances of 5.750(2) and 4.872(1) Å. The shortest interlayer cobalt-cobalt separation through the cbut(4-) skeleton along the crystallographic a-axis is 7.028(2) Å. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic ordering with a Néel temperature of 5.0 K, followed by a field-induced ferromagnetic transition under applied dc fields larger than 1500 Oe. The magnetic structure of 1 has been elucidated at low temperatures in zero field by neutron powder diffraction measurements and was found to be formed by ferromagnetic chains running along the b-axis which are antiferromagnetically coupled with the Co(3) ions through the c-axis giving rise to noncompensated magnetic moments within each bc-layer (ferrimagnetic plane). The occurrence of an antitranslation operation between these layers produces a weak interlayer antiferromagnetic coupling along the a-axis which is overcome by dc fields greater than 1500 Oe resulting in a phase transition toward a ferromagnetic state (metamagnetic behavior).

Synthesis and some properties of anionic chloranilate complexes of iron(iii). Crystal and molecular structure of rubidium and cesium chloranilatoferrates

New anionic chloranilate complexes of iron(iii) Cs[Fe(C6O4Cl2)2(H2O)2]·4H2O (1), Rb[Fe(C6O4Cl2)2(H2O)2]·4H2O (2), Rb2[Fe(C6O4Cl2)2(H2O)2]2·5H2O (3), Cs3Fe(C6O4Cl2)3 (4), (Bu4N)Fe(C6O4Cl2)2 (5), (Bu4N)4Fe2(C6O4Cl2)5 (6), and (R4N)3Fe(C6O4Cl2)3 (R = Pr (7), Bu (8), C5H11 (9)) were synthesized in an aqueous medium. The Mossbauer spectra of the synthesized chloranilatoferrates are characteristic of the high-spin state of FeIII in an octahedral oxygen coordination. The crystal and molecular structures of compounds 1–3 were determined by X-ray diffraction. The complex anions [Fe(C6O4Cl2)2(H2O)2]2− involved in these compounds are composed of two chelate chloranilate ions and two water molecules trans-(1,2) or cis-coordinated (3) to the iron atom. Since tetraalkylammonium tris(chloranilato)ferrates 7–9 and binuclear complex 6 are soluble in many organic solvents, they are promising precursors for the synthesis of metal-organic coordination polymers. Tetrabutylammonium bis(chloranilato)ferrate (Bu4N)Fe(C6O4Cl2)2 (5) is the first example of the preparation of an anionic chloranilate complex of iron(iii) with a plausible chain structure in an aqueous medium.

Molybdenum(VI) Coordination Chemistry of the N,N-Disubstituted Bis(hydroxylamido)-1,3,5-triazine Ligand, H2bihyat. Water-Assisted Activation of the MoVI═O Bond and Reversible Dimerization of cis-[MoVIO2(bihyat)] to [MoVI2O4(bihyat)2(H2O)2

Reaction of the N,N-disubstituted bis(hydroxylamino) ligand 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H(2)bihyat) with cis-[Mo(VI)O(2)(acac)(2)] in tetrahydrofuran resulted in isolation of the mononuclear compound cis-[Mo(VI)O(2)(bihyat)] (1). The treatment of Na(2)Mo(VI)O(4)·2H(2)O with the ligand H(2)bihyat in aqueous solution gave the dinuclear compounds cis-[Mo(VI)(2)O(4)(bihyat)(2)(H(2)O)(2)] (2) and trans-[Mo(VI)(2)O(4)(bihyat)(2)(H(2)O)(2)] (3) at pH values of 3.5 and 5.5, respectively. The structures for the three molybdenum(VI) compounds were determined by X-ray crystallography. Compound 1 has a square-pyramidal arrangement around molybdenum, while in the two dinuclear compounds, each molybdenum atom is in a distorted pentagonal-bipyramidal environment of two bridging and one terminal oxido groups, a tridentate (O,N,O) bihyat(2-) ligand that forms two five-membered chelate rings, and a water molecule trans to the terminal oxido group. The dinuclear compounds constitute rare examples containing the {Mo(2)(VI)O(2)(μ(2)-O(2))}(4+) moiety. The potentiometry revealed that the Mo(VI)bihyat(2-) species exhibit high hydrolytic stability in aqueous solution at a narrow range of pH values, 3-5. A subtle change in the coordination environment of the five-coordinate compound 1 with ligation of a weakly bound water molecule trans to the oxido ligand (1w) renders the equatorial oxido group in 1w more nucleophilic than that in 1, and this oxido group attacks a molybdenum atom and thus the dinuclear compounds 2 and 3 are formed. This process might be considered as the first step of the oxido group nucleophilic attack on organic substrates, resulting in oxidation of the substrate, in the active site of molybdenum enzymes such as xanthine oxidase. Theoretical calculations in the gas phase were performed to examine the influence of water on the dimerization process (1 → 2/3). In addition, the molecular structures, cis/trans geometrical isomerism for the dinuclear molybdenum(VI) species, vibrational spectra, and energetics of the metal-ligand interaction for the three molybdenum(VI) compounds 1-3 have been studied by means of density functional theory calculations.

Thermodynamic and kinetic behaviour of [Pt(2-methylthiomethylpyridine)(OH2)2]2+

The diaqua complex [Pt(2-methylthiomethylpyridine)(OH(2))(2)](2+), Pt(mtp), was synthesized and investigated thermodynamically as well as kinetically. Spectrophotometric acid-base titrations were performed to determine the pK(a) values of the two coordinated water ligands. A low pK(a1) value of 3.15 was observed for the water molecule trans to the pyridine donor, whereas a pK(a2) value of 6.84 was found for the water molecule trans to the labilising sulphur donor. The substitution of coordinated water by a series of sterically hindered S-containing nucleophiles, viz. thiourea (tu), N,N'-dimethylthiourea (dmtu) and N,N,N',N'-tetramethylthiourea (tmtu), was studied under pseudo first-order conditions as a function of nucleophile concentration, pH (2, 4.75, 7.4), temperature and pressure, using stopped-flow techniques and UV-vis spectroscopy. In general the first substitution reaction takes place trans to the sulphur donor. At pH 2 the nucleophiles react in the order tu (634 ± 10) > dmtu (507 ± 5) ≫ tmtu (165 ± 3 M(-1) s(-1) at 25 °C), which is caused by steric hindrance. The second observed reaction involves two steps, viz. the displacement of the second water ligand and dechelation of the pyridine ring with the third-order rate constants 73.3 ± 0.8 (tu), 22.1 ± 0.1 (dmtu) and 6.8 ± 0.2 M(-2) s(-1) (tmtu) at 25 °C. At pH 4.75 the reactions are in general slower due to the presence of aqua-hydroxo species. The same order in reactivity was found, viz. tu (106 ± 1) > dmtu (72 ± 1) ≫ tmtu (14.1 ± 0.5 M(-1) s(-1) at 25 °C). No evidence for ring-dechelation could be observed under these conditions. At pH 7.4 the inert dihydroxo species is predominantly present in solution and consequently no substitution reaction was observed. Quantum chemical calculations were performed to support the interpretation and discussion of the experimental results.

Poly[[diaquabis(μ2-4,4′-bipyridyl)iron(II)] bis{2-[(3-carboxypyridin-2-yl)disulfanyl]nicotinate}

In the title compound, {[Fe(C10H8N2)2(H2O)2](C12H7N2O4S2)2}n, synthesized by hydro­thermal reaction, the 4,4′-bipyridyl ligands (one with symmetry 2, one with symmetry ) connect Fe2+ cations, forming a cationic layer parallel to (001). The coordination of the Fe2+ cation (site symmetry 2) is octahedral, with four N atoms from four 4,4′-bipyridyl ligands and O atoms from two trans water molecules. Adjacent layers are linked with each other by inter­molecular O—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular structure. Parts of the nicotinic acid derivative are equally disordered over two sets of sites.

Manganese complexes with acyclic compartmental Schiff bases

The end-off acyclic compartmental ligands H5-LA and H6-LB have been prepared by [2 + 1] or [3 + 1] condensation of the appropriate amounts of pyridoxal hydrochloride with 1,3-diamine-2-propanol and 3-formylsalicylic acid with tris-2-(aminoethyl)amine, respectively. The ligand H5-LA, which contains two adjacent N2O chambers, bears an endogenous hydroxo potentially bridging group and H6-LB, which contains an inner N4O3 and an outer O3O3 compartment, bears three potentially bridging phenolic groups. The complexes [Mn2(H2-LA)(CH3COO)2](Cl)·5H2O and [Mn(H3-LB)]·0.25H2O·CH3OH have been obtained by the template condensation of the appropriate amine and formyl precursors in the presence of Mn(CH3COO)2·4H2O in methanol. When recrystallized [Mn2(H2-LA)(CH3COO)2](Cl)·5H2O undergoes demetalation reaction giving rise to [Mn(H3-LA)(H2O)2](Cl)(H2O) where the octahedral manganese(III) ion is surrounded by two axial water molecules trans with respect to the equatorial plane formed by the two imine nitrogen atoms and the two phenolate oxygen atoms of the Schiff base [H3-LA]2−. The central –OH group of [H3-LA]2−does not participate in the coordination. In [Mn(H3-LB)]·0.25H2O·CH3OH the octahedral environment about the manganese(III) ion is reached by the coordination of three carboxylate and three phenolate oxygen atoms of the external O3O3 site and the three imine nitrogen atoms are protonated.

Diaqua-bis-(perchlorato)(1,10-phenanthroline)copper(II).

In the title compound, [Cu(ClO4)2(C12H8N2)(H2O)2], the CuII atom is coordinated in a square-planar fashion by the two N atoms of a chelating 1,10-phenanthroline ligand and by two water mol­ecules trans to the N atoms. The coordination sphere of the metal atom is augmented by O atoms of two weakly bonded perchlorate anions, thus yielding a strongly distorted CuN2O4 octa­hedral environment. The crystal packing is stabilized by O—H⋯O hydrogen bonds between the water mol­ecules and the perchlorate anions. In addition, the organic mol­ecules are associated by π–π stacking inter­actions between symmetry-equivalent anti­parallel non-nitro­gen aromatic rings, with inter­planar distances of 3.543 (2) Å.

Polymorphism in the nitrate salt of the [Mn(acetylacetonate)2(H2O)2]+ ion

The crystallization of [Mn(acac)(2)(H(2)O)(2)](+) from solutions containing excess nitrate leads to the formation of four polymorphs. All polymorphs contain two different types of complex ions, one containing essentially coplanar acac ligands and the other in which the two acac ligands together assume a chair conformation. Molecular modelling using DFT (density-functional theory) calculations shows that the coplanar conformation is the electronically stable one. The hydrogen bonding between the trans-water molecules and the nitrate ion produces a one-dimensional chain of 12-membered rings, which are further organized into a two-dimensional network via a lattice water molecule. Lattice-energy calculations have been carried out to compare the stabilities of the four polymorphs.

Poly[[diaquadi-μ-dicyanamido-nickel(II)] bis(pyridinium-4-olate)

The title compound, {[Ni(C2N3)2(H2O)2]·2C5H5NO}n, is a centrosymmetric two-dimensional coordination polymer with a layer (4,4) network structure. The asymmetric unit is compossed of an NiII atom, which sits on an inversion center, a μ-1,5-bridging dicyanamide anion, a water mol­ecule, and a free 4-hydroxy­pyridine mol­ecule present in the zwitterionic pyridinium-4-olate form. The NiII atom is coordinated in a slightly distorted N4O2 octa­hedral geometry by four bridging dicyanamide ligands and two trans water mol­ecules. In the crystal, the two-dimensional networks are linked via N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network.

Manganese(II) and cobalt(II) complexes of 1,4-bis(diphenylphosphinoyl)butane

The title complexes, catena-poly[[[diaquadiethanolmanganese(II)]-mu-1,4-bis(diphenylphosphinoyl)butane-kappa(2)O:O'] dinitrate 1,4-bis(diphenylphosphinoyl)butane solvate], {[Mn(C(2)H(6)O)(2)(C(28)H(28)O(2)P(2))(H(2)O)(2)](NO(3))(2).C(28)H(28)O(2)P(2)}(n), (I), and catena-poly[[[diaquadiethanolcobalt(II)]-mu-1,4-bis(diphenylphosphinoyl)butane-kappa(2)O:O'] dinitrate 1,4-bis(diphenylphosphinoyl)butane solvate], {[Co(C(2)H(6)O)(2)(C(28)H(28)O(2)P(2))(H(2)O)(2)](NO(3))(2).C(28)H(28)O(2)P(2)}(n), (II), are isostructural and centrosymmetric, with the M(II) ions at centres of inversion. The coordination geometry is octahedral, with each metal ion coordinated by two trans ethanol molecules, two trans water molecules and two bridging 1,4-bis(diphenylphosphinoyl)butane ligands which link the coordination centres to form one-dimensional polymeric chains. Parallel chains are linked by hydrogen bonds to uncoordinated 1,4-bis(diphenylphosphinoyl)butane molecules, which are bisected by a centre of inversion. Further hydrogen bonds, weak C-H...O interactions to nitrate anions, and weak C-H...pi interactions serve to stabilize the structure. This study reports a development of the coordination chemistry of bis(diphenylphosphinoyl)alkanes, with the first reported structures of complexes of the first-row transition metals with 1,4-bis(diphenylphosphinoyl)butane.

Hydrothermal syntheses, structures and magnetic properties of coordination frameworks of divalent transition metals

The hydrothermal syntheses, single-crystal X-ray structures and magnetic properties of [Co(C4O4)(H2O)2] (1), [Co3(OH)2(C4O4)2] · 3H2O (2) and [Fe(OH)2(C4O4)] (3) are described. Pale yellow cubes of 1 and brown red crystals of 2 were obtained from the reaction of Co(OH)2 and squaric acid at 200 °C. Brown needle of 3 were obtained similarly from Fe(SO4) · 7H2O, squaric acid and NaOH. 1 consists of a cubic sodalite arrangement with empty cavities where the Co atoms are connected by μ4-squarate and two trans-water molecules each, while 2 and 3 contain metal-hydroxide double-chains of edge-sharing octahedral, brucite-type for 2 and goethite for 3, connected by μ6-squarate. 2 contains water molecules in the channels which can be removed and re-inserted repeatedly without loss of crystallinity. All three compounds possess 3D frameworks made up of coordination and hydrogen bonds. 1 behaves as a paramagnet while 2 and 3 are antiferromagnets and 2 transforms to a ferromagnet reversibly upon dehydration and rehydration. The structures of two one-dimensional polymers employing 2,5-pyridinedicarboxylate, [Co2(H2O)6(2,5-pydc)2] · 2H2O (4) and Cu(2,5-pydc)2 (5), are also reported.

Diaquabis[5-(pyrimidin-2-yl-κN)tetrazolato-κN 1]copper(II)

The title compound, [Cu(C5H3N6)2(H2O)2], is isostructural with the manganese(II) analogue, but different from the two-dimensional structures of the zinc(II), iron(II), cobalt(II) and nickel(II) complexes with the same 5-(pyrimidin-2-yl)tetrazolate ligand. Each of the two symmetry-independent but structurally similar mononuclear molecules in the crystallographic asymmetric unit occupies a special position with the CuII atom on an inversion centre. Both CuII atoms have a highly distorted octahedral coordination geometry formed by two trans water molecules and two chelating ligands. Intermolecular O—H...N hydrogen bonds are present, which lead to the formation of a two-dimensional network.