Formation of N2O from a nickel nitrosyl: isolation of the cis-[N2O2]2- intermediate

Addition of 2,2'-bipyridine (bipy) to [Ni(NO)(bipy)][PF(6)] (1) results in formation of a rare five-coordinate nickel nitrosyl [Ni(NO)(bipy)(2)][PF(6)] (2). This complex exhibits a bent NO(-) ligand in the solid state. On standing in acetonitrile, 2 furnishes the NO coupled product, [Ni(κ(2)-O(2)N(2))(bipy)] (8) in moderate yield. Subsequent addition of 2 equiv of acetylacetone (H(acac)) to 8 results in formation of [Ni(acac)(2)(bipy)], N(2)O, and H(2)O. Preliminary mechanistic studies suggest that the N-N bond is formed via a bimetallic coupling reaction of two NO(-) ligands.     

Dynamic porous coordination polymer based on 2D stacked layers exhibiting high sorption selectivity for CO2

A new dynamic porous coordination polymer (PCP) [Ni(dcpy)(bipy)(0.5)(H(2)O)]·1.5H(2)O (1) was synthesized by assembly of 3-(2',5'-dicarboxylphenyl)pyridine (dcpy), 4,4'-bipyridine (bipy) and NiSO(4)via solvothermal, hydrothermal and microwave methods, displaying a wavelike 2D stacked layer framework. Gas adsorption studies for 1 shows a high selective adsorption of CO(2) over other gases (N(2), CH(4) and CO). The adsorption capacity for N(2) can be moderately altered by different activation temperatures demonstrating the framework flexibility of 1.     

Extended three-dimensional supramolecular architectures derived from trinuclear (bis-beta-diketonato)copper(II) metallocycles

Neutral trinuclear (triangular) copper(II) complexes of type [Cu3L3] incorporating the 1,4-aryl linked bis-beta-diketonato bridging ligands, 1,1-(1,4-phenylene)-bis(butane-1,3-dione) (H2L2), 1,1-(1,4-phenylene)-bis(pentane-1,3-dione) (H2L3) and 1,1-(1,4-phenylene)-bis(4,4-dimethylpentane-1,3-dione) (H2L4) have been demonstrated to react with selected heterocyclic nitrogen donor bases to generate extended supramolecular architectures whose structures have been confirmed by X-ray diffraction. Thus on reaction with 4,4'-bipyridine (bipy), [Cu3(L2)3] yields polymeric structures of type {[Cu3(L2)3(bipy)(THF)] x 2.75THF}n and {[Cu3(L2)3(bipy)(THF)] x bipy x 0.75THF}(n) while with pyrazine (pyz), {[Cu3(L2)3(pyz)] x 0.5THF}n was obtained. Each of these extended structures contain alternating triangle/linker units in a one-dimensional polymeric chain arrangement in which two of the three copper sites in each triangular 'platform' are formally five-coordinate through binding to a heterocyclic nitrogen atom. Interaction of the multifunctional linker unit hexamethylenetetramine (hmt) with [Cu3(L3)3] afforded an unusual, chiral, three-dimensional molecular framework of stoichiometry [Cu3(L3)3(hmt)]n. The latter incorporates the trinuclear units coordinated to three triply bridging hmt units. In marked contrast to the formation of the above structures incorporating bifunctional linker units and five-coordinate metal centres, the trinuclear platform [Cu3(L2)3] reacts with the stronger difunctional base 1,4-diazabicyclo[2.2.2]-octane (dabco) to yield a highly symmetric trigonal columnar species of type {[Cu3(L4)3(dabco)3] x 3H2O}n in which each copper centre is octahedrally coordinated.     

Syntheses and Crystal Structures of One-dimensional Ni（Ⅱ） Complexes with 5-Tert-butyl Isophthalic Acid

Two new Ni（ Ⅱ） coordination polymers, {[Ni（tbip）（bipy）（H2O）]-0.5H2O}n 1 and [Ni（tbip）（phen）（H2O）]n 2 （Hatbip = 5-tert-butyl isophthalic acid, bipy = 2,2＇-bipyridine, phen = 1,10-phenanthroline）, have been synthesized under hydrothermal conditions and characterized by elemental analysis, X-ray diffraction, and IR spectroscopy. In the two polymers, H2tbip acts as a tridentate ligand. Compound 1 has a tbip bridged 1-D linear chain which is extended by hydrogen bonds into a 1-D double chain, while compound 2 exhibits a 1-D zigzag chain.     

Syntheses,Crystal Structures,and Properties of Four Coordination Compounds with Sulfonate-Naphthol Ligand

Russian Journal of General Chemistry - Four coordination compounds, [Zn(ndsp)(bipy)2(H2O)]2·2H2O (1), Mn(ndsp)(bipy)2(H2O)·H2O (2), Ni(ndsp)(bipy)2(H2O) (3),...     

The supramolecular isomerism based on argentophilic interactions: the construction of helical chains with defined right-handed and left-handed helicity

The reactions of racemic and enantiopure macrocyclic compounds [Ni(alpha-rac-L)](ClO(4))(2) (containing equal amounts of SS and RR enantiomers), [Ni(alpha-SS-L)](ClO(4))(2), and [Ni(alpha-RR-L)](ClO(4))(2) with K[Ag(CN)(2)] in acetonitrile/water afford three 1D helical chains of {[Ni(f-rac-L)][Ag(CN)(2)](2)}(n) (1), {[Ni(f-SS-L)](2)[Ag(CN)(2)](4)}(n) (Delta-2), and {[Ni(f-RR-L)](2)[Ag(CN)(2)](4)}(n) (Lambda-2); one dimer of [Ni(f-rac-L)][Ag(CN)(2)](2) (3); and one trimer of [Ni(f-rac-L)Ag(CN)(2)](3).(ClO(4))(3) (4) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). Compounds 1, Delta-2, Lambda-2, and 3, which are supramolecular isomers, are constructed via argentophilic interactions. In 1, [Ni(f-RR-L)][Ag(CN)(2)](2) enantiomers alternately connect with [Ni(f-SS-L)][Ag(CN)(2)](2) enantiomers through intermolecular argentophilic interactions to form a 1D meso-helical chain, and the 1D chains are further connected through the interchain hydrogen bonds to generate a 2D network. When chiral [Ni(alpha-SS-L)](ClO(4))(2) and [Ni(alpha-RR-L)](ClO(4))(2) were used as building blocks, two supramolecular stereoisomers of Delta-2 and Lambda-2 were obtained, which show the motif of homochiral right-handed and left-handed helical chains, respectively, and the 1D homochiral helical chains are linked by the interchain hydrogen bonds to form a 3D structure. In 3, a pair of enantiomers of [Ni(f-RR-L)][Ag(CN)(2)](2) and [Ni(f-SS-L)][Ag(CN)(2)](2) connect with each other through intermolecular argentophilic interactions to form a dimer. The reaction of [Ni(alpha-rac-L)](ClO(4))(2) with K[Ag(CN)(2)] in acetonitrile gives a trimer of 4; each trimer is chiral with unsymmetrical RR, RR, and SS, or RR, SS, and SS configurations. The homochiral nature of Delta-2 and Lambda-2 was confirmed by the results of solid circular dichroism spectra measurements. The solid samples of 1-4 show strong fluorescent emissions at room temperature.     

A 3D polar nanotubular coordination polymer with dynamic structural transformation and ferroelectric and nonlinear-optical properties

A chiral coordination nanotube, [Cd(3)(BPT)(2)(H(2)O)(9)]·2H(2)O (Cd-1; BPT = biphenyl-3,4',5-tricarboxylate), has been synthesized from achiral components and structurally characterized. It consists of homochiral channels based on right-handed helical chains and shows an interdigitated interaction to give a chiral 3D network. The chiral nanotubular framework exhibts dynamic structural transformation upon removal of the guest molecules, and the polarity of this compound induces it to display both ferroelectric and nonlinear-optical properties.     

New synthetic routes to cationic rhenium tricarbonyl bipyridine complexes with labile ligands

Triflate abstraction from the complex [Re(OTf)(CO)(3)(bipy)] (1) using the salt NaBAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl) in dichloromethane solution in the presence of L = PPh(3), NCMe, NCPh, imines, ketones, Et(2)O, THF, MeOH, and MeI affords cationic complexes [Re(L)(CO)(3)(bipy)](+) as their BAr'(4)(-) salts. The new complexes have been characterized spectroscopically and, for [Re(eta(1)-O=C(Me)R)(CO)(3)(bipy)]BAr'(4) (R = CH(3), 6a; R = Ph, 6b), and [Re(THF)(CO)(3)(bipy)]BAr'(4) (9), also by single-crystal X-ray diffraction. Compared with conventional methodologies, the route reported here allows the coordination of a broader range of weakly coordinating ligands and requires considerably milder conditions. On the other hand, the reactions of lithium acetylides with [Re(THF)(CO)(3)(bipy)]BAr'(4) (9) can be used for the high-yield syntheses of rhenium alkynyls [Re(Ctbd1;CR)(CO)(3)(bipy)] (R = Ph, 12; R = SiMe(3), 13). Complex 9 was found to catalyze the aziridination of benzylideneaniline with ethyl diazoacetate.     

Osmabenzenes from the reactions of a dicationic osmabenzyne complex

Treatment of the osmabenzyne Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)Cl(2)(PPh(3))(2) (1) with 2,2'-bipyridine (bipy) and thallium triflate (TlOTf) produces the thermally stable dicationic osmabenzyne [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) (2). The dicationic osmabenzyne 2 reacts with ROH (R = H, Me) to give osmabenzene complexes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf, in which the metallabenzene ring deviates significantly from planarity. In contrast, reaction of the dicationic complex 2 with NaBH(4) produces a cyclopentadienyl complex, presumably through the osmabenzene intermediate [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf. The higher thermal stability of [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf relative to [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf can be related to the stabilization effect of the OR groups on the metallacycle. A theoretical study shows that conversion of the dicationic osmabenzyne complex [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) to a carbene complex by reductive elimination is thermodynamically unfavorable. The theoretical study also suggests that the nonplanarity of the osmabenzenes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf is mainly due to electronic reasons.     

Chiral three-dimensional microporous nickel aspartate with extended Ni-O-Ni bonding

In the course of our investigation aimed at the preparation of homochiral coordination polymers using readily available in optically pure form ligands and building blocks of condensed metal polyhedra, we recently reported a one-dimensional nickel aspartate compound [Ni(2)O(l-Asp)(H(2)O)(2)].4H(2)O (1) based on helical chains with extended Ni-O-Ni bonding. Here we report a new nickel aspartate [Ni(2.5)(OH)(l-Asp)(2)].6.55H(2)O (2) with a three-dimensional Ni-O-Ni connectivity that forms at a higher pH and is based on the same helices as in 1 which are connected by additional nickel octahedra to generate a chiral open framework with one-dimensional channels with minimum van der Waals dimensions of 8 x 5 A. The crystal structure of 2 was determined by synchrotron single-crystal X-ray diffraction on a 10 x 10 x 240 microm crystal.     

Novel coordination frameworks incorporating the 4,4'-bipyrazolyl ditopic ligand

The reaction of the rigid spacer 4,4'-bipyrazole (H(2)BPZ) with late transition metals, either following conventional routes or under solvothermal conditions, afforded the coordination polymers [M(BPZ)]·Solv (M = Zn, 1; Co, 2; Cd, 3; Hg, 4; Cu, 5; Ni, 6; Pd, 7; Solv = DMF, 3; MeCN, 5 and 6; H(2)O, 7), [Cu(H(2)BPZ)(2)(NO(3))(2)] (8), and [Cd(H(2)BPZ)(CH(3)COO)(2)] (9). State-of-the-art laboratory powder diffraction methods allowed to disclose the isomorphous character of 1 and 2, as well as of 5 and 6, which feature 3D porous networks containing 1D channels of square and rhombic shape, respectively. 3, crystallizing in the relatively rare P6(1)22 space group, consists of homochiral helices of octahedral Cd(II) ions, packing in bundles mutually linked by "radial", nonplanar BPZ ligands. Finally, the dense species 8 and 9 contain parallel 2D layers of square and rectangular meshes, respectively. Thermogravimetric analyses witnessed the relevant thermal robustness of all the [M(BPZ)] materials [except the mercury(II) derivative], which are stable in air at least up to 300 °C, with the zinc(II) derivative decomposing only around 450 °C. Variable-temperature powder diffraction experiments highlighted the permanent porosity of 1-3, 5, and 6, retained along consecutive temperature cycles in all cases but 3. When probed with N(2) at 77 K, 1-3 and 5-7 showed Brunauer-Emmett-Teller and Langmuir specific surface areas in the ranges 314(2)-993(11) and 509(16)-1105(1) m(2)/g, respectively.     

Investigation of porous Ni-based metal-organic frameworks containing paddle-wheel type inorganic building units via high-throughput methods

In the search of Ni based metal-organic frameworks (MOFs) containing paddle-wheel type building units, three chemical systems Ni(2+)/H(n)L/base/solvent with H(n)L = H(3)BTC (1,3,5-benzenetricarboxylic acid), H(3)BTB (4,4',4',-benzene-1,3,5-triyl-tris(benzoic acid)), and H(2)BDC (terephthalic acid) were investigated using high-throughput (HT) methods. In addition to the conventional heating, for the first time HT microwave assisted synthesis of MOFs was carried out. Six new compounds were discovered, and their fields of formation were established. In the first system, H(3)BTC was employed and a comprehensive HT-screening of compositional and process parameters was conducted. The synthesis condition for the Ni paddle-wheel unit was determined and two compounds [Ni(3)(BTC)(2)(Me(2)NH)(3)]·(DMF)(4)(H(2)O)(4) (1a) and [Ni(6)(BTC)(2)(DMF)(6)(HCOO)(6)] (1b) were discovered (Me(2)NH = dimethylamine, DMF = dimethylformamide). In the second system, the use of the extended tritopic linker H(3)BTB and the synthesis conditions for the paddle-wheel units led to the porous MOF, [Ni(3)(BTB)(2)(2-MeIm)(1.5)(H(2)O)(1.5)]·(DMF)(9)(H(2)O)(6.5) (2), (2-MeIm = 2-methylimidazole). This compound shows a selective adsorption of H(2)O and H(2) with a strong hysteresis. In the third system, H(2)BDC was used, and the base (DABCO) was incorporated as a bridging ligand into all structures. Thus, two pillared layered porous MOFs [Ni(2)(BDC)(2)(DABCO)]·(DMF)(4)(H(2)O)(1.5) (3a) and [Ni(2)(BDC)(2)(DABCO)]·(DMF)(4)(H(2)O)(4) (3b) as well as a layered compound [Ni(BDC)(DABCO)]·(DMF)(1.5)(H(2)O)(2) (3c) were isolated. The 3a and 3b polymorphs of the [Ni(2)(BDC)(2)(DABCO)] framework can be selectively synthesized. The combination of microwave assisted heating, low overall concentration, stirring of the reaction mixtures, and an excess of DABCO yields a highly crystalline pure phase of 3b. The fields of formation of all compounds were established, and scale-up was successfully performed for 1b, 2, 3a, 3b, and 3c. All compounds were structurally characterized. In addition to IR, elemental and TG analyses, gas and vapor sorption experiments were carried out.     

Inhibitorial effect of the Cu(II) and Ni(II) complexes with polyamines and imidazole derivatives on the Ca,Mg-dependent ATP-ase substrate

The investigation of the inhibitory activity on the Ca,Mg-dependent ATP-ase substrate of some Cu(II) and Ni(II) complexes with polyamines and imidazole derivatives is reported. These results show that the Cu(II) complexes have high inhibitorial effect with the exception of the following very stable compounds: square planar [Cu(N-PropIm)₂(NCS)₂], distorted octahedral [Cu(bipy)₂(NCS)₂] and five coordinate [Cu(Me₆tren)(NCS)] (SCN). The Ni(II) derivatives present a medium inhibitorial activity except to the stable tetrahedral [Ni(N-PropIm)₂(NCS)₂], hexacoordinate [Ni(dpt)(tn)(NCS)] (SCN) and fivecoordinate [Ni(dpt)(tn)]Br₂ and [Ni(Me₆tren)(NCS)] (SCN). An explanation of these conclusions is reported.     

Kinetics and mechanism of the interaction of pentaammine(pyridine-2-carboxylato)cobalt(III) ions with hexaaquanickel(II) and nickel(II) complexes: the role of chelating ligands

The reversible complexation of the pentaammine(pyridine-2-carboxylato)cobalt(III) ion [N5Co{O2C-(2)-C5H4 N}]2+ [N5=5HN3 and tetraethylenepentaammine (tetren)] with NiIIL(OH2)6-n [L=H2O (N5=tetren); L=bipy, ida2- (iminodiacetate) and nta3- (nitrilotriacetate), N5=5NH3 and tetren] has been investigated by the stopped-flow technique at 20-40 degC, and I= 0.3mol dm-3. At 25degC, the rate constants, kf(dm3 mol-1s-1), DeltaH(kJmol-1) and DeltaS(JK-1mol-1) for the formation of the ternary complexes [(tetren)-CoIII{O2C-(2)-C5H4N} NiIIL(OH2)6-n] are as follows: L=H2O, 530+9, 53+2, -15+7, respectively; L=bipy, 640+30, 37+3, -65+9; L=ida2-, 3900+100, 47+3, -18+11; L=nta3-, 10200+400, 49+1, −2+2. Nickel(II), in the ternary complexes, is chelated by the free pyridyl-N and the carboxylato moiety of the pyridine-2-carboxylate bound to the cobalt centre. The formation rate constant (kf) and the associated activation parameters are relatively insensitive to the N5 moieties for a given ligand L; kf increased in the order: Ni(OH2)62+Ni(bipy)(OH2)42+ Ni(ida)(OH2)3 (nta)(OH2)2-. Data analysis indicated that the mechanism shifted from the dissociative interchange (Id) to the chelation-controlled one, with the decrease of the available sites for coordination in NiIIL(OH2)6−n. The rate constants (kr) for the dissociation of [N5CoIII{O2C-(2)-C5 H4N}NiIIL(OH2) 6-(n+2)] to the parent reactants indicated steric acceleration [krL(5NH3) <krL(tetren)] and followed the trend: krNi(nta)->kr Ni(ida) >krNi(bipy)2+ for both pentaammine substrates. The chelate ring opening rate constants for the ternary complexes were estimated, from which it was apparent that the tetren envelope of cobalt(III) exerted relatively greater steric pressure as compared with 5NH3 in favouring opening up of the chelate ring. This revised version was published online in June 2006 with corrections to the Cover Date.     

From model compounds to protein binding: syntheses, characterizations and fluorescence studies of [RuII(bipy)(terpy)L]2+ complexes (bipy = 2,2'-bipyridine; terpy = 2,2':6',2''-terpyridine; L = imidazole, pyrazole and derivatives, cytochrome c)

Compounds [RuII(bipy)(terpy)L](PF6)2 with bipy = 2,2'-bipyridine, terpy = 2,2':6',2"-terpyridine, L = H2O, imidazole (imi), 4-methylimidazole, 2-methylimidazole, benzimidazole, 4,5-diphenylimidazole, indazole, pyrazole, 3-methylpyrazole have been synthesized and characterized by 1H NMR, ESI-MS and UV/Vis (in CH3CN and H2O). For L = H2O, imidazole, 4,5-diphenylimidazole and indazole the X-ray structures of the complexes have been determined with the crystal packing featuring only few intermolecular C-H...pi or pi-pi interactions due to the separating action of the PF6-anions. Complexes with L = imidazole and 4-methylimidazole exhibit a fluorescence emission with a maximum at 662 and 667 nm, respectively (lambdaexc= 475 nm, solvent CH3CN or H2O). The substitution of the aqua ligand in [Ru(bipy)(terpy)(H2O)]2+ in aqueous solution by imidazole to give [Ru(bipy)(terpy)(imi)]2+ is fastest at a pH of 8.5 (as followed by the increase in emission intensity). Coupling of the [Ru(bipy)(terpy)]2+ fragment to cytochrome c(Yeast iso-1) starting from the Ru-aqua complex was successful at 35 degrees C and pH 7.0 after 5 d under argon in the dark. The [Ru(bipy)(terpy)(cyt c)]-product was characterized by UV/Vis, emission and mass spectrometry. The location where the [Ru(bipy)(terpy)] complex was coupled to the protein was identified as His44 (corresponding to His39 in other numbering schemes) using digestion of the Ru-coupled protein by trypsin and analysis of the tryptic peptides by HPLC-high resolution MS.     

Interdigitation, interpenetration and intercalation in layered cuprous tricyanomethanide derivatives

Reaction of Cu(I), tricyanomethanide (tcm , C(CN)3-) and L = either hexamethylenetetramine (hmt), 4,4'-bipyridine (bipy) or 1,2-bis(4-pyridyl)ethene (bpe) gives crystals of [Cu(tcm)(hmt)] (1), [Cu(tcm)(bipy)] (2) and [Cu(tcm)(bpe)] x 0.25 bpe x 0.5 MeCN (3), respectively. Crystal structure analysis shows 1-3 all contain closely related puckered (4,4) sheets composed of tetrahedral Cu(I) ions bridged by 2-connecting tcm- and L. The crystal packing, however, varies markedly with L. In 1 the sheets interdigitate in pairs. In 2 the sheets participate in parallel interpenetration in pairs. In 3 guest bpe and MeCN molecules are intercalated in channels formed by the stacking of the sheets.     

Fe(bipy)(CN)(4)](-) as a versatile building block for the design of heterometallic systems: synthesis, crystal structure, and magnetic properties of PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O, [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O, and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O [bipy = 2,2'-Bipyridine; M = Mn and Zn

The new cyano complexes of formulas PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O (1), [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O with M = Mn (2) and Zn (3), and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O (4) [bipy = 2,2'-bipyridine and PPh(4) = tetraphenylphosphonium cation] have been synthesized and structurally characterized. The structure of complex 1 is made up of mononuclear [Fe(bipy)(CN)(4)](-) anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of a chelating bipy and four carbon atoms of four terminal cyanide groups, building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral centrosymmetric [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] heterotrinuclear units and crystallization water molecules. The [Fe(bipy)(CN)(4)](-) entity of 1 is present in 2 and 3 acting as a monodentate ligand toward M(H(2)O)(4) units [M = Mn(II) (2) and Zn(II) (3)] through one cyanide group, the other three cyanides remaining terminal. Four water molecules and two cyanide nitrogen atoms from two [Fe(bipy)(CN)(4)](-) units in trans positions build a distorted octahedron surrounding Mn(II) (2) and Zn(II) (3). The structure of the [Fe(phen)(CN)(4)](-) complex ligand in 2 and 3 is close to that of the one in 1. The intramolecular Fe-M distances are 5.126(1) and 5.018(1) A in 2 and 3, respectively. 4 exhibits a neutral one-dimensional polymeric structure containing two types of [Fe(bipy)(CN)(4)](-) units acting as bismonodentate (Fe(1)) and trismonodentate (Fe(2)) ligands versus the divalent zinc cations through two cis-cyanide (Fe(1)) and three fac-cyanide (Fe(2)) groups. The environment of the iron atoms in 4 is distorted octahedral as in 1-3, whereas the zinc atom is pentacoordinated with five cyanide nitrogen atoms, describing a very distorted square pyramid. The iron-zinc separations across the single bridging cyanides are 5.013(1) and 5.142(1) A at Fe(1) and 5.028(1), 5.076(1), and 5.176(1) A at Fe(2). The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. 1 is a low-spin iron(III) complex with an important orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the antiferromagnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10 A) being very weak. More interestingly, 2 exhibits a significant intramolecular antiferromagnetic interaction between the central spin sextet and peripheral spin doublets, leading to a low-lying spin quartet.     

Multinuclear NMR studies of the products resulting from the reaction of pyridine or 2,2'-bipyridine with [Rh4(CO)12

The progressive addition of anhydrous pyridine, (py), to a solution of [Rh(4)(CO)(12)] in CH(2)Cl(2) under CO, even at low temperature, results in immediate disproportionation to give cis-[Rh(CO)(2)py(2)][Rh(5)(CO)(15)]; further addition of pyridine results in the progressive replacement of CO's by py on the same apical rhodium in [Rh(5)(CO)(15)](-) to give cis-[Rh(CO)(2)py(2)][Rh(5)(CO)(15-x)py(x)] (x = 1, 2). The analogous reactions with 2,2'-bipyridine (bipy) give only [Rh(CO)(2)bipy][Rh(5)(CO)(13)bipy]. IR and low temperature, multinuclear NMR measurements have been used to establish the structures of all the above anions and the structures of [Rh(5)(CO)(13)(bipy)](-) and [Rh(5)(CO)(13)py(2)](-) are subtly different. Under N(2), [Rh(4)(CO)(12)] reacts with py to give [Rh(6)(CO)(16-y)py(y)] (y = 1, 2).     

M(rac-N-benzyl Asp)(H2O)] (M = Co, Ni): noncentrosymmetric coordination polymeric chains with racemic chiral ligands

The hydrothermal reaction of fumaric acid, benzylamine, and metal salts yielded M[(rac-N-benzyl-Asp)(H(2)O)] (M = Co, Ni), 1 and 2, and Ni[(rac-N-benzyl-Asp)(H(2)O)(3)]·H(2)O 3. Under mild hydrothermal conditions, Michael addition of benzylamine to fumaric acid led to the formation of a racemic mixture of N-benzyl aspartic acid enantiomers. The noncentrosymmetric structures of 1 and 2 consist of one-dimensional polymeric chains in which metal cations are bridged by d- and l-N-benzyl aspartate anions alternating along the chain. The centrosymmetric structure of 3 is composed of discrete Ni[(rac-N-benzyl-Asp)(H(2)O)(3)] units that are connected by hydrogen bonds into layers. The single layers are homochiral but are hydrogen bonded to similar homochiral layers that contain the N-benzyl aspartate with the opposite handedness. Compounds 1 and 2 showed second harmonic generation (SHG), and their magnetic and thermodynamic properties are described.     

A homochiral luminescent 2D porous coordination polymer with collagen-type triple helices showing selective guest inclusion

A homochiral luminescent porous coordination polymer, [Cd(L)(H(2)O)]·3H(2)O, with interconnected collagen like triple-helical chains has been synthesized solvothermally by using cadmium(II) salt and a newly designed d-isosorbide-based, enantiomerically pure chiral ligand. The framework is a 2D porous material and forms a 1D channel along the a axis, with the channel dimensions ~6.2 × 4.4 ?(2). The compound has high selectivity in the uptake of water and methanol over other solvents (e.g., tetrahydrofuran, ethanol, benzene, and cyclohexane) inside the channels.