Solvent Water Molecules Research Articles

One-dimensional Cu(II) coordination polymers containing C2h-symmetric 1,1':4',1''-terphenyl-3,3'-dicarboxylate linkers.

Two new one-dimensional Cu(II) coordination polymers (CPs) containing the C2h-symmetric terphenyl-based dicarboxylate linker 1,1':4',1''-terphenyl-3,3'-dicarboxylate (3,3'-TPDC), namely catena-poly[[bis(dimethylamine-κN)copper(II)]-μ-1,1':4',1''-terphenyl-3,3'-dicarboxylato-κ(4)O,O':O'':O'''] monohydrate], {[Cu(C20H12O4)(C2H7N)2]·H2O}n, (I), and catena-poly[[aquabis(dimethylamine-κN)copper(II)]-μ-1,1':4',1''-terphenyl-3,3'-dicarboxylato-κ(2)O(3):O(3')] monohydrate], {[Cu(C20H12O4)(C2H7N)2(H2O)]·H2O}n, (II), were both obtained from two different methods of preparation: one reaction was performed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a potential pillar ligand and the other was carried out in the absence of the DABCO pillar. Both reactions afforded crystals of different colours, i.e. violet plates for (I) and blue needles for (II), both of which were analysed by X-ray crystallography. The 3,3'-TPDC bridging ligands coordinate the Cu(II) ions in asymmetric chelating modes in (I) and in monodenate binding modes in (II), forming one-dimensional chains in each case. Both coordination polymers contain two coordinated dimethylamine ligands in mutually trans positions, and there is an additional aqua ligand in (II). The solvent water molecules are involved in hydrogen bonds between the one-dimensional coordination polymer chains, forming a two-dimensional network in (I) and a three-dimensional network in (II).

Structure and packing of aminoxyl and piperidinyl acrylamide monomers.

The closely related title compounds, 4-acrylamido-2,2,6,6-tetramethylpiperidine-1-oxyl, C12H21N2O2, (I), and N-(2,2,6,6-tetramethylpiperidin-4-yl)acrylamide monohydrate, C12H22N2O·H2O, (II), are important monomers in the preparation of redox-active polymers. They comprise an acrylamide group of the usual s-cis configuration appended to a 2,2,6,6-tetramethyl-substituted piperidine-1-oxyl radical or a piperidinyl chair, respectively. The adjacent amide and piperidinyl H atoms are approximately trans across the C-N bond. The packing in (I) is dominated by N-H...O hydrogen bonds; these are supported by C-H...O contacts to form an R2(1)(6) ring repeat, a motif which has been observed in other acrylamide structures. In (II), hydrogen bonds are again key to the packing arrangements. In this case, the incorporated solvent water molecule acts as an acceptor through its O atom and as a donor through both H atoms, binding three adjacent piperidinylacrylamide molecules into layers. In both structures, weak C-H...O contacts involving the piperidinyl methyl H atoms and a proximal acrylamide carbonyl O atom extend the structure in the third dimension.

A new Co(II) complex of diniconazole: synthesis, crystal structure and antifungal activity.

A new Co(II) complex of diniconazole, namely diaqua[(E)-(RS)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl-κN(4))pent-1-en-3-ol]cobalt(II) dinitrate dihydrate, [Co(C15H17Cl2N3O)3(H2O)2](NO3)2·2H2O, was synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal structural analysis shows that the centrosymmetric Co(II) cation is coordinated by four diniconazole ligands and two water molecules, forming a six-coordinated octahedral structure. There are also two free nitrate counter-anions and two additional solvent water molecules in the structure. Intermolecular O-H...O hydrogen bonds link the complex cations into a one-dimensional chain. In addition, the antifungal activity of the complex against Botryosphaeria ribis, Gibberella nicotiancola, Botryosphaeria berengriana and Alternariasolani was studied. The results indicate that the complex shows a higher antifungal activity for Botryosphaeria ribis and Botryosphaeria berengriana than diniconazole, but a lower antifungal activity for Gibberella nicotiancola and Alternariasolani.

Crystal structure of an unknown solvate of dodecakis-(μ2-alaninato-1:2κ(2) O:N,O)cerium(III)hexa-nickel(II) aqua-tris-(hydroxido-κO)tris-(nitrato-κ(2) O,O')cerate(III).

The chiral title compound, [CeNi6(C3H6NO2)12][Ce(NO3)3(OH)3(H2O)], comprises a complex heterometallic Ni/Ce cation and a homonuclear Ce anion. Both the cation and anion exhibit point group symmetry 3. with the CeIII atom situated on the threefold rotation axis. The cation metal core consists of six NiII atoms coordinated in a slightly distorted octa­hedral N2O4 configuration by N and O atoms of 12 deprotonated l-alaninate ligands exhibiting both bridging and chelating modes. This metal–organic coordination motif encapsulates one CeIII atom that shows an icosa­hedral coordination by the O-donor atoms of the l-alaninate ligands, with Ce—O distances varying in the range 2.455 (5)–2.675 (3) Å. In the anion, the central CeIII ion is bound to three bidentate nitrate ligands, to three hydroxide ligands and to one water mol­ecule, with Ce—O distances in the range 2.6808 (19)–2.741 (2) Å. The H atoms of the coordinating water mol­ecule are disordered over three positions due to its location on a threefold rotation axis. Disorder is also observed in fragments of two l-alaninate ligands, with occupancy ratios of 0.608 (14):0.392 (14) and 0.669 (8):0.331 (8), respectively, for the two sets of sites. In the crystal, the complex cations and anions assemble through O—H⋯O and N—H⋯O hydrogen bonds into a three-dimensional network with large voids of approximately 1020 Å3. The contributions of highly disordered ethanol and water solvent mol­ecules to the diffraction data were removed with the SQUEEZE procedure [Spek (2015 ▸). Acta Cryst. C71, 9–18]. The given chemical formula and other crystal data do not take into account the unknown amount of these solvent mol­ecules.

Proton Migration in Clusters Consisting of Protonated Pyridine Solvated by Water Molecules.

Proton transfer (PT) from protonated pyridine to water molecules is observed after excitation of microhydrated protonated pyridine (Py) clusters PyH(+) (H2 O)n (n=0-5) is induced by a single collision with an Ar atom at high incident velocity (95×10(3) m s(-1) ). Besides the fragmentation channel associated with the evaporation of water molecules, the charged-fragment mass spectrum shows competition between the production of the PyH(+) ion (or its corresponding charged fragments) and the production of H(+) (H2 O) or H(+) (H2 O)2 ions. The increase in the production of protonated water fragments as a function of the number of H2 O molecules in the parent cluster ion as well sd the observation of a stable H(+) (H2 O)2 fragment, even in the case of the dissociation of PyH(+) (H2 O)2 , are evidence of the crucial role of PT in the relaxation process, even for a small number of solvating water molecules.

Crystal structure of chlorido-(2-{[2-(phenyl-car-bamo-thioyl)hydrazin-1-ylidene](pyridin-2-yl)methyl}pyridin-1-ium)gold(I) chloride sesqui-hydrate.

The title complex, [AuCl(C18H16N5S)]Cl·1.5H2O, may be considered as a gold(I) compound with the corresponding metal site coordinated by a thio-semicarbazone ligand through the S atom. The ligand adopts an E conformation and the gold(I) atom displays the expected linear geometry with a Cl atom also bonded to the metal ion [Cl-Au-S = 174.23 (5)°]. One of the pyridyl rings is protonated, giving the gold complex an overall positive charge. Two solvent water mol-ecules, one of which is located on a twofold rotation axis, and a non-coordinating chloride ion complete the structural assembly. The mol-ecular structure is stabilized by intra-molecular and inter-molecular N-H⋯Cl, N-H⋯N, O-H⋯Cl and O-H⋯O hydrogen bonding.

A two-dimensional cadmium(II) polymer based on nicotinic acid and thiocyanate ligands.

A cadmium-thiocyanate complex, poly[[bis(nicotinic acid-κN)di-μ-thiocyanato-κ(2)N:S;κ(2)S:N-cadmium(II)] monohydrate], {[Cd(NCS)2(C6H5NO2)2]·H2O}n, was synthesized by the reaction of nicotinic acid, cadmium nitrate tetrahydrate and potassium thiocyanide in aqueous solution. In the crystal structure, each Cd(II) cation is in a distorted octahedral coordination environment, coordinated by the N and S atoms of nicotinic acid and thiocyanate ligands. Neighbouring Cd(II) cations are linked together by thiocyanate bridges to form a two-dimensional network. Hydrogen-bond interactions between the uncoordinated solvent water molecules and the organic ligands result in the formation of the three-dimensional supramolecular network.

Crystal structure of l-tryptophan-fumaric acid-water (1/1/1).

In the title compound, C11H12N2O2·C4H4O4·H2O, the l-tryp­to­phan mol­ecule crystallized as a zwitterion, together with a neutral fumaric acid mol­ecule and a water solvent mol­ecule. In the crystal, the three components are linked by a series of N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, forming slabs lying parallel to (001). The slabs are connected by O—H⋯O hydrogen bonds, involving inversion-related fumaric acid groups, leading to the formation of a three-dimensional structure.

Crystal structure of poly[[hexa-qua-1κ(4) O,2κ(2) O-bis-(μ3-pyridine-2,4-di-car-box-ylato-1κO (2):2κ(2) N,O (2');1'κO (4))cobalt(II)-strontium(II)] dihydrate

In the title polymeric complex, {[CoSr(C7H3NO4)2(H2O)6]·2H2O}n, the CoII ion, which is situated on a crystallographic centre of inversion, is six-coordinated by two O atoms and two N atoms from two pyridine-2,4-di­carboxyl­ate (pydc2−) ligands and two terminal water mol­ecules in a slightly distorted octa­hedral geometry, to form a trans-[Co(pydc)2(H2O)2]2− unit. The SrII ion, situated on a C 2 axis, is coordinated by four O atoms from four pydc2− ligands and four water mol­ecules. The coordination geometry of the SrII atom can be best described as a distorted dodeca­hedron. Each SrII ion bridges four [Co(pydc)2(H2O)2]2− units by four COO− groups of four pydc2− ligands to form a three-dimensional network structure. Two additional solvent water mol­ecules are observed in the crystal structure and are connected to the three-dimensional coordination polymer by O—H⋯O hydrogen bonds. Further intra- and intermolecular O—H⋯O hydrogen bonds consolidate the overall structure.

Crystal structure of poly[[di-μ2-aqua-aqua-sodium] 4-amino-3,5,6-tri-chloro-pyridine-2-carboxyl-ate trihydrate], the sodium salt of the herbicide picloram.

In the structure of the title complex, {[Na(H2O)3](C6H2Cl3N2O2)·3H2O} n , the sodium salt of the herbicide picloram, the cation adopts a polymeric chain structure, based on μ2-aqua-bridged NaO5 trigonal-bipyramidal complex units which have, in addition, a singly bonded water mol-ecule. Each of the bridges within the chain, which extends parallel to the a axis, is centrosymmetric, with Na⋯Na separations of 3.4807 (16) and 3.5109 (16) Å. In the crystal, there are three water mol-ecules of solvation and these, as well as the coordinating water mol-ecules and the amino group of the 4-amino-3,5,6-tri-chloro-picolinate anion, are involved in extensive inter-species hydrogen-bonding inter-actions with carboxyl and water O atoms, as well as the pyridine N atom. Among these associations is a centrosymmetric cyclic tetra-water R 4 (4)(8) motif, resulting in an overall three-dimensional structure.

Crystal structure of bis-[tris-(1,10-phenanthroline-κ(2) N,N')cobalt(II)] tetra-nitrate N,N'-(1,4-phenyl-enedicarbon-yl)diglycine solvate octa-hydrate.

The complex cation of the title compound, [Co(C12H8N2)3]2(NO3)4·C12H12N2O6·8H2O, contains a Co(II) atom with a distorted octa-hedral coordination environment defined by six N atoms from three bidentate 1,10-phenanthroline ligands. The asymmetric unit of the title compound is completed by one-half of the N,N'-(1,4-phenyl-enedicarbon-yl)diglycine solvent mol-ecule, which is located on a centre of inversion, by two nitrate counter-anions and four solvent water mol-ecules. Two [Co(C12H8N2)3](2+) cations are connected through C-H⋯O contacts and through lone-pair⋯π inter-actions involving the non-coordinating N,N'-(1,4-phenyl-enedicarbon-yl)diglycine and phenanthroline mol-ecules. The different aromatic ring systems are involved in π-π stacking and C-H⋯π inter-actions, with centroid-to-centroid distances in the range 3.7094 (8)-3.9973 (9) Å. The crystal structure is stabilized by further anion⋯π inter-actions and C-H⋯O contacts, as well as O-H⋯O and N-H⋯O hydrogen bonds between water mol-ecules, the non-coordinating nitrate anions, N,N'-(1,4-phenyl-enedicarbon-yl)diglycine and phenanthroline mol-ecules. These non-covalent inter-actions give rise to a three-dimensional supra-molecular network.

Structures and acidity constants of arsenite and thioarsenite species in hydrothermal solutions

We report a first principles molecular dynamics (FPMD) study of structures and acidity constants of arsenite and thioarsenite species in liquid water from ambient temperature to 573K. The analyses show that at all temperatures, the OH ligands of arsenite species form H-bonds with solvating water molecules as both donors and acceptors, whereas there are only very weak H-bonds between the SH ligands of thioarsenite species and water. For both arsenites and thioarsenites, the dangling O/S sites form strong H-bonds with hydrogen atoms of water molecules, but the As atoms have almost no interaction with water molecules. The FPMD based vertical energy gap method was applied to calculate the acidity constants. With the evaluated acidity, the species distributions with respect to pH have been derived. The pKa1s of H3AsO3 and H3AsS3 demonstrate a decreasing trend with temperature. For arsenites, H3AsO3 and H2AsO3− can coexist, whereas HAsO32− almost does not exist, due to the notably high pKa2s of H3AsO3. For thioarsenites, H2AsS3− and HAsS32− are always the dominant species in the near neutral pH range from ambient temperature to 573K.

Synthesis and crystal structures of two coordination polymers and a binuclear cadmium(II) complex containing 3- and 4-aminobenzoate ligands.

Due to their wide range of coordination modes and versatile conformations when binding to metal atoms, multicarboxylate ligands are of interest in the design of metal-organic frameworks (MOFs). Three Cd(II) complexes, namely catena-poly[diammonium [[chloridocadmium(II)]-di-μ-chlorido-[chloridocadmium(II)]-bis(μ-3-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N]], {(NH4)[CdCl2(C7H6NO2)]}n, (I), catena-poly[[[aquacadmium(II)]-bis(μ-4-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N] monohydrate], {[Cd(C7H6NO2)2(H2O)]·H2O}n, (II), and di-μ-acetato-κ(4)O:O'-bis[(4-aminobenzoato-κ(2)O,O')(2,2'-bipyridine-κ(2)N,N')cadmium(II)], [Cd2(CH3COO)2(C7H6NO2)2(C10H8N2)2], (III), with different stuctural forms are reported. Complex (I) has a one-dimensional ladder structure, with strong N-H···O and weak N-H···Cl hydrogen bonds linking the cations and anions in the three-dimensional supramolecular structure. Complex (II) has a one-dimensional chain structure. Extensive O-H···O and N-H···O hydrogen bonds between the anionic ligands and the solvent water molecules and π-π stacking interactions between the centroids of the benzene rings lead to the three-dimensional supramolecular structure. Complex (III) is a binuclear molecule which is extended into a three-dimensional supramolecular structure via strong N-H···O and weak C-H···O hydrogen bonds.

Solvation and Desolvation Phenomenon and in-Situ NMR Studies on Stripping/Plating of Magnesium Metal in Magnesium Batteries

Multivalent batteries are promising technologies that can potentially outperform lithium ion batteries in term of energy density, power density and unit cost.1 Among which magnesium batteries have attracted much attention over the last a few years. However, scientific challenges continue primarily due to the lack of understanding of the intercalation mechanism of multivalent ions.2 Our recent study is devoted to the understanding of the solvation and desolvation effect with 1H and 2D solid-state NMR spectroscopy by probing the movement of the water molecules and solvent molecules in the system (Bis(trifluoromethan sulfonyl)Imide dissolved in diglyme based magnesium batteries) at various charge states. It is suggested that the water and diglyme molecules play a crucial role in facilitating the intercalation of the magnesium ions in the cathode lattice upon charging and discharging. 3 In addition, the effective stripping and plating effect on the magnesium metal is also investigated. By taking advantage of in situ NMR spectroscopy, we investigate metal vs metal pseudo cells while the cells are polarized. No significant changes in the NMR spectra between the pristine and cycled pseudo cell for Grignard electrolytes, which is in agreements with reversible smooth stripping and plating. 1 D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature 2000, 407, 724-727 10.1038/35037553. 2 H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy & Environmental Science 2013, 6, 2265-2279 10.1039/c3ee40871j. 3 S. H. Lapidus, N. N. Rajput, X. Qu, K. W. Chapman, K. A. Persson, P. J. Chupas, Physical Chemistry Chemical Physics 2014, 16, 21941-21945 10.1039/c4cp03015j.

Crystal structure of [NaZn(BTC)(H2O)4]·1.5H2O (BTC = benzene-1,3,5-tri-carb-oxy-l-ate): a heterometallic coordination compound.

The title coordination polymer, poly[[μ-aqua-tri­aqua­(μ3-benzene-1,3,5-tri­carboxyl­ato)sodiumzinc] sesquihydrate], {[NaZn(C9H3O6)(H2O)4]·1.5H2O}n, was obtained in ionic liquid microemulsion at room temperture by the reaction of benzene-1,3,5-tri­carb­oxy­lic acid (H3BTC) with Zn(NO3)2·6H2O in the presence of NaOH. The asymmetric unit comprises two Na+ ions (each located on an inversion centre), one Zn2+ ion, one BTC ligand, four coordinating water mol­ecules and two solvent water molecules, one of which is disordered about an inversion centre and shows half-occupation. The Zn2+ cation is five-coordinated by two carboxyl­ate O atoms from two different BTC ligands and three coordinating H2O mol­ecules; the Zn—O bond lengths are in the range 1.975 (2)–2.058 (3) Å. The Na+ cations are six-coordinated but have different arrangements of the ligands: one is bound to two carboxyl­ate O atoms of two BTC ligands and four O atoms from four coordinating H2O mol­ecules while the other is bound by four carboxyl­ate O atoms from four BTC linkers and two O atoms of coordinating H2O mol­ecules. The completely deprotonated BTC ligand acts as a bridging ligand binding the Zn2+ atom and Na+ ions, forming a layered structure extending parallel to (100). An intricate network of O—H⋯O hydrogen bonds is present within and between the layers.

Two novel organic–inorganic hybrid compounds with straight and zigzag chain alignments of Cu(II) centers: Synthesis, crystal structure, spectroscopy, thermal analysis and magnetism

Two hybrid salts, viz. bis(guanidinium) bis(oxalato)cuprate(II) (1) and bis(2-aminopyridinium) bis(oxalato)cuprate(II) trihydrate (2) have been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction and SQUID magnetometry. Compounds 1 and 2 crystallize in the monoclinic P21/c and triclinic P1¯ space groups, respectively. In both structures, the four-coordinated Cu(II) ion in [Cu(C2O4)2]2− unit weakly interacts with two axial O-atoms of neighboring units to build a prolate CuO6 octahedron, with regular axial Cu–O bonds of 2.825Å in 1, whereas in 2 two different Cu–O bonds (2.814Å and 2.701Å) are found. In 1, stacking of [Cu(C2O4)2]2− units across internal symmetry-related O-atoms results in equidistantly spaced monomers, thus forming straight Cu(II) chains with regular spacing of Cu⋯Cu=3.582Å. By contrast, in 2, stacking of the [Cu(C2O4)2]2− entities occurs via external symmetry-related O-atoms, yielding zigzag Cu(II) chains with shorter intra-dimer spacing of [Cu⋯Cu]intra=3.430Å and longer inter-dimer spacing of [Cu⋯Cu]inter=4.961Å. The anhydrated compound 1 is stable up to 250°C, whereas the hydrated compound 2 shows a significant weight loss of solvent water molecules at about 70°C, followed by the decomposition of the network. The magnetic measurements in the 2–300K temperature range revealed weak antiferromagnetic coupling in the two hybrid salts.

Probing the Hydrogen-Bonded Water Network at the Active Site of a Water Oxidation Catalyst: [Ru(bpy)(tpy)(H2O)](2+)·(H2O)(0-4).

The infrared spectra of gas-phase mass-selected [Ru(bpy)(tpy)(H2O)](2+)·(H2O)(0-4) clusters (bpy = 2,2'-bipyridine; tpy = 2,2':6,2″-terpyridine) in the OH stretching region are reported. These species are formed by bringing the homogeneous water oxidation catalyst [Ru(bpy)(tpy)(H2O](2+) from solution into the gas phase via electrospray ionization (ESI) and reconstructing the water network at the active site by condensing additional water onto the complex in a cryogenic ion trap. Infrared predissociation spectroscopy is used to probe the structure of these clusters via their distinctive OH stretch frequencies, which are sensitive to the shape and strength of the local hydrogen-bonding network. The analysis of the spectra, aided by electronic structure calculations, highlights the formation of strong hydrogen bonds between the aqua ligand and the solvating water molecules in the first solvation shell. These interactions are found to propagate through the subsequent solvation shells and lead to the stabilization of asymmetric solvation motifs. Electronic structure calculations show that these strong hydrogen bonds are promoted by charge transfer from the H atom of the aqua ligand to the Ru-OH2 bond.

Crystal structure of aqua-{μ-N-[3-(di-methyl-amino)-prop-yl]-N'-2-(oxidophen-yl)oxamidato}(1,10-phen-anthroline-5,6-dione)dicopper(II) perchlorate hemihydrate.

The title compound, [Cu2(C13H16N3O3)(C12H6N2O2)(H2O)]ClO4·0.5H2O, consists of a cis-oxamide-bridged binuclear Cu(II) complex cation, a perchlorate anion and half a solvent water mol-ecule. One Cu(II) cation is N,N',N",O-chelated by an N-[3-(di-methyl-amino)-prop-yl]-N'-(2-hy-droxy-phen-yl)oxamide trianion in a distorted square-planar geometry, whereas the other Cu(II) cation is O,O'-chelated by the oxamide moiety of the anion and N,N'-chelated by a 1,10-phenanthroline-5,6-dione mol-ecule, and a water mol-ecule further coordinates the second Cu(II) cation, completing a distorted square-pyramidal coordination geometry. In the crystal, classical O-H⋯O hydrogen bonds, weak C-H⋯O hydrogen-bonding inter-actions and π-π stacking inter-actions link the complex cations, anions and solvent water mol-ecules into a three-dimensional supra-molecular architecture. In the crystal, the di-methyl-amino-propyl unit of the oxamide anion is disordered over two positions with an occupancy ratio of 0.561 (11):0.439 (11); the solvent water mol-ecule is also disordered over two positions, the occupancy ratio being 0.207 (10):0.293 (10).

Can the Absence of Isotope Scrambling in the Wacker Oxidation of Allyl Alcohol Disprove Outer Sphere Hydroxypalladation?

The major controversy regarding the mechanism of the Wacker oxidation of alkenes at low [Cl(-)] concerns the mechanism of nucleophilic attack of a solvent water molecule on alkene. Most of the recent mechanistic studies on the Wacker oxidation of ethene have reported that nucleophilic attack occurs by an outer sphere mechanism and not by an inner sphere mechanism. One of the crucial experimental findings in support of the inner sphere mechanism is that isotope scrambling does not take place when deuterated ally alcohol was oxidized under the standard Wacker conditions. In this work, we try to explain these experimental results in the framework of the outer sphere mechanism. We simulated the Wacker oxidation of allyl alcohol using ab initio molecular dynamics (AIMD) techniques in order to probe the detailed mechanism, free-energy profiles, and the rate-determining step. Our simulations show that the mechanism of allyl alcohol oxidation follows outer sphere hydroxypalladation, and the rate-determining step involves Cl(-) ligand isomerization, contradicting the conclusions from the isotope scrambling experiments. However, by carrying out microkinetic modeling based on the free-energy barriers of the elementary steps obtained from our AIMD simulations, we also observe no isotope scrambling. This led us to determine the genesis of the observed absence of isotope scrambling. Most importantly, here we demonstrate that the absence of isotope scrambling is in fact consistent with the outer sphere hydroxypalladation and cannot disprove it.

Crystal structure of catena-poly[[[tetra-aqua-zinc(II)]-μ-1,4-bis-[4-(1H-imidazol-1-yl)benzo-yl]piperazine] dinitrate monohydrate

In the title polymeric complex, {[Zn(C24H22N6O2)(H2O)4](NO3)2·2H2O}n, the ZnII cation, located about a twofold rotation axis, is coordinated by two imidazole groups and four water mol­ecules in a distorted N2O4 octa­hedral geometry; among the four coordinate water mol­ecules, two are located on the same twofold rotation axis. The 1,4-bis­[4-(1H-imidazol-1-yl)benzo­yl]piperazine] ligand is centro-symmetric, with the centroid of the piperazine ring located on an inversion center, and bridges the ZnII cations, forming polymeric chains propagating along [201]. In the crystal, O—H⋯O and weak C—H⋯O hydrogen bonds link the polymeric chains, nitrate anions and solvent water mol­ecules into a three-dimensional supra­molecular architecture. A short O⋯O contact of 2.823 (13) Å is observed between neighboring nitrate anions.