Lead hydro sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: synthesis and structure determination by combining X-ray rietveld refinement, 1H MAS NMR FTIR and XANES spectroscopy

Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths.     

Cyano-bridged structures based on [MnIIN3O2-macrocycle)]2+: a synthetic, structural, and magnetic study

Reactions between the complex [MnII(L)]2+, where L is a N3O2 macrocyclic ligand, and different cyanometalate precursors such as [M(CN)n]m- (M(III) = Cr, Fe; M(II) = Fe, Ni, Pd, Pt) lead to cyano-bridged molecular assemblies exhibiting a variety of structural topologies. The reaction between [MnII(L)]2+ and [FeII(CN)6]4- forms a trinuclear complex with formula [(MnII(L)(H2O))2(FeII(micro-CN)2(CN)4)] x 2MeOH x 10H2O (1) which crystallizes in the triclinic space group P1. The reaction between [MnII(L)]2+ and [M(II)(CN)4]2-, where M(II) = Ni (2), Pd (3), Pt (4), gives rise to three isostructural linear chain compounds with stoichiometry [(MnII(L))(M(II)(micro-CN)2(CN)2)]n and which crystallize in the monoclinic space group C2/c. The self-assembly between [MnII(L)]2+ with [M(III)(CN)6]3-, where M(III) = Cr (5), Fe (6, 7, 8), forms three types of compounds. Compounds 5 and 6 are isostructural (monoclinic, space group P2(1)/n), and the structures comprise anionic linear chains [(MnII(L))(M(III)(micro-CN)2(CN)4)]n(n-) with cationic trinuclear complexes [(MnII(L)(H2O))2(M(III)(micro-CN)2(CN)4)]+ as counterions. Using an excess of K3[FeIII(CN)6], an analogous compound to 6 but with K+ as counterion is obtained (7), which crystallizes in the triclinic space group P1. Compound 8 consists of 2-D layers with formula [(MnII(L))3(FeIII(micro-CN)4(CN)2)(FeIII(micro-CN)2(CN)4)]n x 2nMeOH; it crystallizes in the monoclinic space group P2(1)/n. The magnetic properties were investigated for all samples. In particular, compound 5, which shows antiferromagnetic exchange interactions between Mn(II) and Cr(III) ions through cyanide bridging ligands, has been studied in detail; the magnetic exchange parameter amounts to J = -7.5(7) cm(-1). Compound 8 shows a magnetically ordered phase below 6.4 K which is confirmed by M?ssbauer spectroscopy; two hyperfine split spectra were observed below Tc from which IJI values of 2.1 and 1.6 cm(-1) could be deduced.     

CH(A2Delta) Formation in hydrocarbon combustion: the temperature dependence of the rate constant of the reaction C2H + O2--> CH(A2Delta) + CO2

The temperature dependence of the rate constant of the chemiluminescence reaction C2H + O2 --> CH(A) + CO2, k1e, has been experimentally determined over the temperature range 316-837 K using pulsed laser photolysis techniques. The rate constant was found to have a pronounced positive temperature dependence given by k1e(T) = AT(4.4) exp(1150 +/- 150/T), where A = 1 x 10(-27) cm(3) s(-1). The preexponential factor for k1e, A, which is known only to within an order of magnitude, is based on a revised expression for the rate constant for the C2H + O(3P) --> CH(A) + CO reaction, k2b, of (1.0 +/- 0.5) x 10(-11) exp(-230 K/T) cm3 s(-1) [Devriendt, K.; Van Look, H.; Ceursters, B.; Peeters, J. Chem. Phys. Lett. 1996, 261, 450] and a k2b/k1e determination of this work of 1200 +/- 500 at 295 K. Using the temperature dependence of the rate constant k1e(T)/k1e(300 K), which is much more accurately and precisely determined than is A, we predict an increase in k(1e) of a factor 60 +/- 16 between 300 and 1500 K. The ratio of rate constants k2b/k1e is predicted to change from 1200 +/- 500 at 295 K to 40 +/- 25 at 1500 K. These results suggest that the reaction C2H + O2 --> CH(A) + CO2 contributes significantly to CH(A-->X) chemiluminescence in hot flames and especially under fuel-lean conditions where it probably dominates the reaction C2H + O(3P) --> CH(A) + CO.     

A novel cationic heteropolyoxovanadium(IV) cluster functionalized with organic ligands: synthesis and characterization of the fully reduced species [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]Cl2

The solvothermal reaction of (HOCH2CH2)3N with [(n-C4H9)4N]3[H3V10O28] and MnCl2 x 4H2O in CH3CN and CH3OH yields a novel cationic heteropolyoxovanadium(IV) cluster, [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]2+, containing a fully reduced new cyclic [MnV6N6O18] core with the Anderson structure.     

Organic-inorganic hybrids based on novel bimolecular [Si2W22Cu2O78(H2O)]12- polyoxometalates and the polynuclear complex cations [Cu(ac)(phen)(H2O)]n n+ (n=2, 3)

The reaction of a monosubstituted Keggin polyoxometalate (POM) generated in situ with copper-phenanthroline complexes in excess ammonium or rubidium acetate led to the formation of the hybrid metal organic-inorganic compounds A7[Cu2(ac)2(phen)2(H2O)2][Cu3(ac)3(phen)3(H2O)3][Si2W22Cu2O78(H2O)].approximately 18 H2O (A=NH4+ (1), Rb+ (2); ac=acetate; phen=1,10-phenanthroline). These compounds are constructed from inorganic and metalorganic interpenetrated sublattices containing the novel bimolecular Keggin POM, [Si2W22Cu2O78(H2O)]12-, and Cu-ac-phen complexes, [Cu(ac)(phen)(H2O)]n n+ (n=2, 3). The packing of compound 1 can be viewed as a stacking of open-framework layers parallel to the xy plane built of hydrogen-bonded POMs, and zigzag columns of pi-stacked Cu-ac-phen complex cations running along the [111] direction. Magnetic and EPR results are discussed with respect to the crystal structure of the compounds. DFT calculations on [Cu(ac)(phen)(H2O)]n n+ cationic complexes have been performed, to check the influence of packing in the complex geometry and determine the magnetic exchange pathways.     

First hexadecavanadate compound: hydrothermal synthesis and characterization of a three-dimensional framework [(Cu(1,2-pn)2)7(V16O38(H2O))2].4H2O

The hydrothermal reaction of V2O5, Cu(CH3COO)2.H2O, 1,2-diaminopropane and [N(CH3)4]OH yields the novel three-dimensional open-framework solid [(Cu(1,2-pn)2)7-(V16O38(H2O))2].4H2O constructed from the new mixed-valence [V16O38(H2O)]7- clusters interconnected through mu 2-[Cu(1,2-pn)2]2+ groups.     

Formation, reactivity, and photorelease of metal bound nitrosyl in [Ru(trpy)(L)(NO)](n+) (trpy = 2,2':6',2'-terpyridine, L = 2-phenylimidazo[4,5-f]1,10-phenanthroline)

Nitrosyl complexes with {Ru-NO} (6) and {Ru-NO} (7) configurations have been isolated in the framework of [Ru(trpy)(L)(NO)] ( n+ ) [trpy = 2,2':6',2'-terpyridine, L = 2-phenylimidazo[4,5- f]1,10-phenanthroline] as the perchlorate salts [ 4](ClO 4) 3 and [ 4](ClO 4) 2, respectively. Single crystals of protonated material [ 4-H (+)](ClO 4) 4.2H 2O reveal a Ru-N-O bond angle of 176.1(7) degrees and triply bonded N-O with a 1.127(9) A bond length. Structures were also determined for precursor compounds of [ 4] (3+) in the form of [Ru(trpy)(L)(Cl)](ClO 4).4.5H 2O and [Ru(trpy)(L-H)(CH 3CN)](ClO 4) 3.H 2O. In agreement with largely NO centered reduction, a sizable shift in nu(NO) frequency was observed on moving from [ 4] (3+) (1953 cm (-1)) to [ 4] (2+) (1654 cm (-1)). The Ru (II)-NO* in isolated or electrogenerated [ 4] (2+) exhibits an EPR spectrum with g 1 = 2.020, g 2 = 1.995, and g 3 = 1.884 in CH 3CN at 110 K, reflecting partial metal contribution to the singly occupied molecular orbital (SOMO); (14)N (NO) hyperfine splitting ( A 2 = 30 G) was also observed. The plot of nu(NO) versus E degrees ({RuNO} (6) --> {RuNO} (7)) for 12 analogous complexes [Ru(trpy)(L')(NO)] ( n+ ) exhibits a linear trend. The electrophilic Ru-NO (+) species [ 4] (3+) is transformed to the corresponding Ru-NO 2 (-) system in the presence of OH (-) with k = 2.02 x 10 (-4) s (-1) at 303 K. In the presence of a steady flow of dioxygen gas, the Ru (II)-NO* state in [ 4] (2+) oxidizes to [ 4] (3+) through an associatively activated pathway (Delta S++ = -190.4 J K (-1) M (-1)) with a rate constant ( k [s (-1)]) of 5.33 x 10 (-3). On irradiation with light (Xe lamp), the acetonitrile solution of paramagnetic [Ru(trpy)(L)(NO)] (2+) ([ 4] (2+)) undergoes facile photorelease of NO ( k NO = 2.0 x 10 (-1) min (-1) and t 1/2 approximately 3.5 min) with the concomitant formation of the solvate [Ru (II)(trpy)(L)(CH 3CN)] (2+) [ 2'] (2+). The photoreleased NO can be trapped as an Mb-NO adduct.     

An unprecedented copper(I,II)-octacyanotungstate(V) 2-D network: crystal structure and magnetism of [CuII(tren)]{CuI[W(V)(CN)8]} . 1.5H2O

A novel two-dimensional cyanide-bridged polymer [CuII(tren)]{CuI[W(V)(CN)8]} . 1.5H2O (tren = tris(2-aminoethyl)amine) formed via the simultaneous in situ metal-ligand redox reaction of [Cu(tren)(OH2)]2+ and self-assembly with [W(V)(CN)8]3- consists of a {CuI[W(V)(CN)8]} square grid built of CuI centres of tetrahedral geometry coordinatively saturated by CN bridges and [W(V)(CN)8]3- capped by [CuII(tren)]2+ moieties; it exhibits ferromagnetic coupling J1 = +5.8(1) cm(-1) within the CuII-W(V) dinuclear subunits and weak antiferromagnetic coupling J2 = -0.03(1) cm(-1) between them through diamagnetic CuI spacers.     

Heterometallic MIIRuIII2 compounds constructed from trans-[Ru(Salen)(CN)2]- and trans-[Ru(Acac)2(CN)2]-. Synthesis, structures, magnetic properties, and density functional theoretical study

The synthesis, structures, and magnetic properties of four cyano-bridged M(II)Ru(III)2 compounds prepared from the paramagnetic Ru(III) building blocks, trans-[Ru(salen)(CN)2]- 1 [H2salen = N,N'-ethylenebis(salicylideneimine)] and trans-[Ru(acac)2(CN)2]- (Hacac = acetylacetone), are described. Compound 2, {Mn(CH3OH)4[Ru(salen)(CN)2]2}.6CH3OH.2H2O, is a trinuclear complex that exhibits antiferromagnetic coupling between Mn(II) and Ru(III) centers. Compound 3, {Mn(H2O)2[Ru(salen)(CN)2]2.H2O}n, has a 2-D sheetlike structure that exhibits antiferromagnetic coupling between Mn and Ru, leading to ferrimagnetic-like behavior. Compound 4, {Ni(cyclam)[Ru(acac)2(CN)2]2}.2CH3OH.2H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane), is a trinuclear complex that exhibits ferromagnetic coupling. Compound 5, {Co[Ru(acac)2(CN)2]2}n, has a 3-D diamond-like interpenetrating network that exhibits ferromagnetic ordering below 4.6 K. The density functional theory (DFT) method was used to calculate the molecular magnetic orbitals and the magnetic exchange interaction between Ru(III) and M(II) (Mn(II), Ni(II)) ions.     

Cyanide-bridged Mn(III)-Fe(III) bimetallic complexes based on the pentacyano(1-methylimidazole)ferrate(III) building block: structure and magnetic characterizations

Seven cyanide-bridged bimetallic complexes have been synthesized by the reaction of [Fe(1-CH3im)(CN)5]2- with Mn(III) Schiff base complexes. Their crystal structure and magnetic properties have been characterized. Five complexes, [Mn2(5-Brsalen)2Fe(CN)5(1-CH3im)] x H2O (1), [Mn2(5-Clsalen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (2), [Mn2(5-Clsaltn)2(H2O)2Fe(CN)5(1-CH3im)] (3), [Mn2(5-Clsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (4), and [Mn2(5-Brsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x CH3OH (5), are neutral and trinuclear with two [Mn(SB)]+ (SB2- = Schiff base ligands) and one [Fe(1-CH3im)(CN)5]2-. Complex {[Et4N][Mn(acacen)Fe(CN)5(1-CH3im)]}n x 6nH2O (6) is one-dimensional with alternate [Mn(acacen)]+ and [Fe(CN)5(1-CH3im)]2- units. The two-dimensional complex {[Mn4(saltmen)4Fe(CN)5(1-CH3im)]}n[ClO4]2n x 9nH2O (7) consists of Mn4Fe units which are further connected by the phenoxo oxygen atoms. Magnetic studies show the presence of ferromagnetic Mn(III)-Fe(III) coupling in the trinuclear compounds with the magnetic coupling constant (J) ranging from 4.5 to 6.0 cm-1, based on the Hamiltonian H = -2JSFe(SMn(1) + SMn(2)). Antiferromagnetic interaction has been observed in complex 6, whereas ferromagnetic coupling occurs in complex 7. Complexes 6 and 7 exhibit long-range magnetic ordering with a TN value of 4.0 K for 6 and Tc of 4.8 K for 7. Complex 6 shows metamagnetic behavior at 2 K, and complex 7 possesses a hysteresis loop with a coercive field of 500 Oe, typical of a soft ferromagnet.     

Synthesis and Structure of a POMs-based 3D Zeolike Ionic Crystal, {[Co（dpdo）2（H2O）2（CH3CN）]2（SiMo12O40）（H2O）2}n

A POMs-based 3D zeolike ionic crystal 1, {[Co（dpdo）2（CH3CN）（H2O）2]2（SiMo12O40）- （HEO）2}n （dpdo = 4,4＇-bipyridine-N,N＇-dioxide）, was constructed via self-assembly by embedding Keggintype [SiMo12O40]^4- polyanions within the intercrystalline voids as pillars and structurally characterized. The crystal structure was determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P1 with a = 11.430（3）, b = 12.242（3）, c = 14.279（3）A, α = 106.196（4）,β = 94.316（4）, γ = 98.294（3）°, V = 1884.5（7）A^3 Z = 1, C44H50N10O54CoEMo12Si, Mr = 2880.17, Dc = 2.538 g/cm^3, p = 2.484 mm^-1,F（000） = 1388, the final R = 0.0383 and wR = 0.1096 for 7753 observed reflections with I 〉 2σ（I）. Flack factor is 0.22（3）. Compound 1 is a pillar-layered framework with the [SiMo12O40]^4- anions linearly located on the square voids between the 2D bilayers which are formed by the dpdo ligands and cobalt（II） ions.     

Existence of doubly charged lead monohydrate: experimental evidence and theoretical examination

Despite reports to the contrary, doubly charged lead monohydrate is a stable species against both proton and charge transfers. [Pb(H(2)O)](2+) has been observed as a minor product in the ligand-exchange reaction of [Pb(CH(3)CN)](2+) with H(2)O after collisional activation. Density functional theory has been used to examine reaction profiles of [Pb(H(2)O)(n)](2+) where n = 1, 2, and 3.     

Gas-phase reactivity of heterobinuclear oxometalate anions [CrMoO6(OR)]-, [CrWO6(OR)]-, and [MoWO6(OR)]- (R = H, nBu)

Heterobinuclear oxometalate anions based upon [CrMoO7]2-, [CrWO7]2-, and [MoWO7]2- were generated and transferred to the gas phase by the electrospray process from acetonitrile solutions containing two of the salts (Bu4N)2[MO4] (M = Cr, Mo, W). Their reactivities were examined and compared with those of the related homobinuclear anions based upon [M2O7]2- (M = Cr, Mo, W). Particular emphasis was placed upon reactions relevant to gas-phase catalytic cycles described previously for oxidation of alcohols by [Mo2O6(OH)]- (Waters, T.; O'Hair, R. A. J.; Wedd, A. G. J. Am. Chem. Soc. 2003, 125, 3384-3396). The protonated anions [MM'O6(OH)]- each reacted with methanol with loss of water to form [MM'O6(OCH3)]- at a rate that was intermediate between those of [M2O6(OH)]- and [M'2O6(OH)]-. The butylated anions [MM'O6(OBu)]- were generated by collisional activation of the ion-pairs {Bu4N+ [MM'O7]2-}-. Collisional activation of [MM'O6(OBu)]- resulted in either the loss of butanal (redox reaction) or the loss of butene (elimination reaction), with the detailed nature of the observations depending on the nature of both M and M'. Selective 18O labeling indicated that the butoxo ligands of [CrMoO6(OBu)]- and [CrWO6(OBu)]- were located on molybdenum and tungsten, respectively. This structural insight allowed a more detailed comparison of reactivity with the homobinuclear species, and highlighted the importance of the neighboring metal center in these reactions.     

Synthesis of new poly(propylenimine) dendrimers DAB-dendr-[NH(O)COCH2CH2OC(O)C5H4Rh(NBD)](n) [n=4, 8, 16, 32, 64] functionalized with alkoxycarbonylcyclopentadienyl complexes of rhodium(I)

The reaction between [Rh[C5H4CO2(CH)2OH](NBD)] (1) and 1,1'-carbonyldiimidazole (CDI) leads to the new CO2-imidazole functionalized alkoxycarbonylcyclopentadienyl complex [Rh[C5H4CO2(CH2)2O2C-Im](NBD)] (2) (Im=imidazole). The latter was treated with five generations of poly(propylenimine) dendrimers DAB-dendr-(NH2)(n) [n=4, 8, 16, 32, 64] (DAB=diaminobutane) to accomplish the synthesis of the new organometallic dendritic macromolecules DAB-dendr-[NH(O)COCH2CH2OC(O)C5H4Rh(NBD)](n) [n=4 (4), 8 (5), 16 (6), 32 (7), 64 (8)] based on flexible poly(propylenimine) dendrimer cores, built up to the fifth generation. Spectroscopic characterization of all the new compounds will be presented and discussed.     

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.     

Metal ion-controlled self-assembly using pyrimidine hydrazone molecular strands with terminal hydroxymethyl groups: a comparison of Pb(II) and Zn(II) complexes

Metal complexation studies were performed with the ditopic pyrimidine-hydrazone (pym-hyz) strand 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) and Pb(ClO(4))(2)·3H(2)O, Pb(SO(3)CF(3))(2)·H(2)O, Zn(SO(3)CF(3))(2), and Zn(BF(4))(2) to examine the ability of 1 to form various supramolecular architectures. X-ray crystallographic and NMR studies showed that coordination of the Pb(II) salts with 1 on a 2:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2) resulted in the linear complexes [Pb(2)1(ClO(4))(4)] (2), [Pb(2)1(ClO(4))(3)(H(2)O)]ClO(4) (3), and [Pb(2)1(SO(3)CF(3))(3)(H(2)O)]SO(3)CF(3) (4). Two unusually distorted [2 × 2] grid complexes, [Pb1(ClO(4))](4)(ClO(4))(4) (5) and [Pb1(ClO(4))](4)(ClO(4))(4)·4CH(3)NO(2) (6), were formed by reacting Pb(ClO(4))(2)·6H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2). These grids formed despite coordination of the hydroxymethyl arms due to the large, flexible coordination sphere of the Pb(II) ions. A [2 × 2] grid complex was formed in solution by reacting Pb(SO(3)CF(3))(2)·H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN as shown by (1)H NMR, microanalysis, and ESMS. Reacting the Zn(II) salts with 1 on a 2:1 metal/ligand ratio gave the linear complexes [Zn(2)1(H(2)O)(4)](SO(3)CF(3))(4)·C(2)H(5)O (7) and [Zn(2)1(BF(4))(H(2)O)(2)(CH(3)CN)](BF(4))(3)·H(2)O (8). (1)H NMR studies showed the Zn(II) and Pb(II) ions in these linear complexes were labile undergoing metal ion exchange. All of the complexes exhibited pym-hyz linkages in their cisoid conformation and binding between the hydroxymethyl arms and the metal ions. No complexes were isolated from reacting either of the Zn(II) salts with 1 on a 1:1 metal/ligand ratio, due to the smaller size of the Zn(II) coordination sphere as compared to the much larger Pb(II) ions.     

Synthesis and Crystal Structure of an Ion-pair Compound:[H2(teta)]2+·[Ni(CN)4]2-·2H2O(teta=Meso-5,7,7,12,14,14-hexamethyl- 1,4,8,11-tetraazacyclotetradecane)

The ion-pair compound [H2(teta)]2+·[Ni(CN)4] 2-·2H2O (C20H42N8NiO2, teta = meso- 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) was synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P21/n with a = 10.0784(10), b = 9.5411(7), c = 14.1010(14)(A), β= 106.752(2)o, V = 1298.4(2) (A)3, Mr = 485.33, Z = 2, Dc = 1.241 g/cm3,μ(MoKα) = 0.778 mm-1 and F(000) = 524. The structure was refined to R = 0.0391 and wR = 0.0870 for 2614 observed reflections with I > 2σ(I). The title compound contains one [Ni(CN)4]2- anion, one protonated macrocyclic tetraamine cation [H2(teta)]2+ and two water molecules. There are multiform hydrogen bonds in the compound to link the different components and stabilize the crystal structure.     

Delta(DeltaS) and Delta(DeltaS) for the competing bond cleavage reactions in (CH3CN)(ROH)H+ [R = CH3, C2H5, C3H7, (CH3)2CH

Microcanonical variational transition-state theory was used to determine the entropies of activation for hydrogen-bond cleavage reactions leading to CH(3)CN + ROH(2)(+) in a series of acetonitrile-alcohol proton-bound pairs (CH(3)CN)(ROH)H(+) (where R = CH(3), CH(3)CH(2), CH(3)CH(2)CH(2), and (CH(3))(2)CH). In each case, the dissociation potential surface was modelled at the MP2/6-31 + G(d) level of theory. The dissociating configurations having the minimum sums-of-states were identified in each case and the resulting entropies of activation were calculated. Combined with previous work on the competing reaction leading to CH(3)CNH(+) + ROH, the results permitted the determination of the Delta(DeltaS) in each proton-bound pair. For the (CH(3)CN)(CH(3)OH)H(+) and (CH(3)CN)(CH(3)CH(2)OH)H(+) proton-bound pairs, the entropies of activation for the two dissociating channels are essentially the same [i.e., Delta(DeltaS) = 0], while Delta(DeltaS) for the propanol-containing pairs ranged between 40 and 45 J K(-1) mol(-1). The latter non-zero values are due to a combination of the location of the dividing surface in each dissociation and the rapidity with the frequencies of the vanishing vibrational modes go to zero as they are converted to product translations and rotations during the dissociation.     

Cyano-bridged homometallic 1-D and bimetallic 2-D assemblies: synthesis,structures, and magnetic properties of [Ni(baepn)(CN)]n(ClO4)n and [Ni(baepn)]2n[Fe(CN)(6)]n(H2O)8n

Cyano-bridged homometallic complex [Ni(baepn)(CN)](n)(ClO(4))(n)(1) and bimetallic complex [Ni(baepn)](2)(n)[Fe(CN)(6)](n)(H(2)O)(8)(n)(2) [baepn = N,N'-bis(2-aminoethyl)-1,3-propanediamine] were synthesized and characterized. 1 crystallizes in the monoclinic space group P2(1)/n with a = 9.560(3) A, b = 10.700(3) A, c = 14.138(9) A, beta = 90.18(6) degrees, and Z = 4; 2 crystallizes in the monoclinic space group P2(1)/c with a = 8.951(2) A, b = 13.672(3) A, c = 14.392(3) A, beta = 98.906(4) degrees, and Z = 4. The complex 1 has one-dimensional structure whose chain vector runs along the b axis with baepn ligands and perchlorate anions alternately arranged up and down in the c direction. The antiferromagnetic nature of 1 was explained in terms of the infinite chain model and Haldane gap, giving g = 2.33, J = -29.4 cm(-1), and the magnitude of Haldane gap E(g) = 5.22 K. The complex 2 that constitutes the first example of 2-D bimetallic assembly of Ni(II) ion and ferrocyanide anion is composed of the neutral layers based on the [Ni(4)Fe(4)] square grid spanning in the bc plane. For 2, the analysis with the Curie-Weiss law in 2-300 K range results in THETA = 0.200 K and the magnetism was explained in terms of the ability of ferrocyanide in the -Ni-NC-Fe-CN-Ni unit to promote ferromagnetic Ni-Ni interaction.     

Reflected shock tube studies of high-temperature rate constants for CH3 + O2, H2CO + O2, and OH + O2

The reflected shock tube technique with multipass absorption spectrometric detection of OH-radicals at 308 nm, corresponding to a total path length of approximately 2.8 m, has been used to study the reaction CH3 + O2 CH2O + OH. Experiments were performed between 1303 and 2272 K, using ppm quantities of CH3I (methyl source) and 5-10% O2, diluted with Kr as the bath gas at test pressures less than 1 atm. We have also reanalyzed our earlier ARAS measurements for the atomic channel (CH3 + O2 --> CH3O + O) and have compared both these results with other earlier studies to derive a rate expression of the Arrhenius form. The derived expressions, in units of cm3 molecule(-1) s(-1), are k = 3.11 x 10(-13) exp(-4953 K/T) over the T-range 1237-2430 K, for the OH-channel, and k = 1.253 x 10(-11) exp(-14241 K/T) over the T-range 1250-2430 K, for the O-atom channel. Since CH2O is a major product in both reactions, reliable rates for the reaction CH2O + O2 --> HCO + HO2 could be derived from [OH]t and [O]t experiments over the T-range 1587-2109 K. The combined linear least-squares fit result, k = 1.34 x 10(-8) exp(-26883 K/T) cm3 molecule(-1) s(-1), and a recent VTST calculation clearly overlap within the uncertainties in both studies. Finally, a high sensitivity for the reaction OH + O2 --> HO2 + O was noted at high temperature in the O-atom data set simulations. The values for this obtained by fitting the O-atom data sets at later times (approximately 1.2 ms) again follow the Arrhenius form, k = 2.56 x 10(-10) exp(-24145 K/T) cm3 molecule(-1) s(-1), over the T-range, 1950-2100 K.