Poly[μ7‐sulfanediyldiacetato‐disilver(I)]

In the title coordination polymer, [Ag₂(C₄H₄O₄S)], each Ag^I cation is four‐coordinated by three of the four carboxylate O atoms and the S atom from symmetry‐related sulfanediyldiacetate ligands, thus defining a distorted tetrahedral geometry at the metal centre. The Ag^I cations are bridged by sulfanediyldiacetate groups, leading to a two‐dimensional layer structure. These layers are interconnected via Ag—S bonds to form a three‐dimensional coordination polymer network overall.     

catena‐Poly[[nickel(II)‐μ2‐[1,3‐bis(imidazol‐1‐ylmethyl)benzene‐κ2N3:N3′]‐μ2‐(5‐carboxybenzene‐1,3‐dicarboxylato‐κ4O1,O1′:O3,O3′)] 0.41‐hydrate]

The title compound, {[Ni(C₉H₄O₆)(C₁₄H₁₄N₄)]·0.41H₂O}_n, exhibits a three‐dimensional hydrogen‐bonded supramolecular framework. The Ni^II cation is six‐coordinated in a distorted triangular prism defined by two N atoms from two 1,3‐bis(imidazol‐l‐ylmethyl)benzene (bix) ligands and four O atoms from two 5‐carboxybenzene‐1,3‐dicarboxylate (HBTC) dianions. The bix molecules and HBTC dianions both act as bidentate ligands, linking the Ni^II cations to form a one‐dimensional coordination polymer. A two‐dimensional wave‐like net is constructed by O—H...O hydrogen bonds linking adjacent chains. Partially occupied solvent water molecules fill the cavities and link these layers to form a three‐dimensional supramolecular structure via O—H...O hydrogen bonds. The title compound was also characterized by powder X‐ray diffraction and thermogravimetric analysis.     

A novel one‐dimensional double‐chain‐like ZnII coordination polymer: poly[bis(1‐benzyl‐1H‐imidazole‐κN3)tris(μ‐cyanido‐κ2C:N)(cyanido‐κC)disilver(I)zinc(II)]

One of most interesting systems of coordination polymers constructed from the first‐row transition metals is the porous Zn^II coordination polymer system, but the numbers of such polymers containing N‐donor linkers are still limited. The title double‐chain‐like Zn^II coordination polymer, [Ag₂Zn(CN)₄(C₁₀H₁₀N₂)₂]_n, presents a one‐dimensional linear coordination polymer structure in which Zn^II ions are linked by bridging anionic dicyanidoargentate(I) units along the crystallographic b axis and each Zn^II ion is additionally coordinated by a terminal dicyanidoargentate(I) unit and two terminal 1‐benzyl‐1H‐imidazole (BZI) ligands, giving a five‐coordinated Zn^II ion. Interestingly, there are strong intermolecular Ag^I…Ag^I interactions between terminal and bridging dicyanidoargentate(I) units and C—H…π interactions between the phenyl rings of BZI ligands of adjacent one‐dimensional linear chains, providing a one‐dimensional linear double‐chain‐like structure. The supramolecular three‐dimensional framework is stabilized by C—H…π interactions between the phenyl rings of BZI ligands and by Ag^I…Ag^I interactions between adjacent double chains. The photoluminescence properties have been studied.     

A Novel Coordination Polymer, [Ag4^1 （bpdc）（H2bpdc）（Hbpdc）2]n （bpdc = 2,2＇-bipyridyl-3,3＇-dicarboxylate）： Coordination Models of bpdc Ligands

A novel coordination polymer, [Ag₄ppdc)(H₂bpdc)(Hbpdc)₂] (bpdc = 2,2′‐bipyridyl‐3,3′‐dicarboxylate), was hydrothermally synthesized at 403 K and structurally characterized by single crystal X‐ray diffraction analysis. The compound crystalizes in the monoclinic space group C2/c with a=1.9516(4) nm, b=1.9503(4) nm. c=1.2566(3) nm, and β=112.48(3)°. In the two‐dimensional crystal structure, Ag^I center is coordinated, in a scarce coordination environment, double‐capped tetrahedron, by one bpdc ligand to form N‐Ag‐N chelate bond via two pyridyl N atoms, and other two bpdc ligands to form two O‐Ag‐O chelate bonds, respectively, via two carboxyl O atoms. The bpdc ligands are present in one non‐protonated form, bpdc, and two protonated forms, Hbpdc and H2bpdc, which all act as μ3‐ligand in a hexadentate fashion (N, N′; O, O′; O, O′) to coordinate with three Ag centers, respectively, through the three chelate bonds. This coordinated fashion of bpdc ligand is first found in the title compound. W‐Us‐NIR reflectance spectroscopy study revealed insulator nature for the crystal with an optical energy gap of 3.1 eV.     

Bis(1,3,5‐triazine‐2,4,6‐triamine‐κN1)silver(I) nitrate

The title compound, [Ag(C₃H₆N₆)₂]NO₃, has an alternating two‐dimensional bilayer structure supported by extensive hydrogen bonds. The [Ag(melamine)₂]⁺ cationic monomers (melamine is 1,3,5‐triazine‐2,4,6‐triamine) are connected via N—H...N hydrogen bonds to form two‐dimensional sheets. Nitrate groups are sandwiched between two sheets through N—H...O hydrogen bonds. An almost perfectly linear coordination geometry is found for the Ag^I ions. The triazine ligands are slightly distorted due to π–π interactions.     

Synthesis of Nickel(II) Azacorroles by Pd‐Catalyzed Amination of α,α′‐Dichlorodipyrrin NiII Complex and Their Properties

Synthesis of nickel(II) complexes of meso‐aryl‐substituted azacorroles was performed by Buchwald–Hartwig amination of a dipyrrin Ni^II complex with benzylamine through C? N and C? C coupling. The highly planar structure of Ni^II azacorroles was elucidated by X‐ray diffraction analysis. ¹H NMR analysis and nucleus independent chemical shift (NICS) calculation on Ni^II azacorrole revealed its distinct aromaticity with [17]triaza‐annulene 18π conjugation. In addition, acylation of azacorrole selectively afforded N‐ and C‐acylated azacorroles depending on the reaction conditions, showing the dual reactivity of azacorroles.     

A one‐dimensional silver(I) coordination polymer based on 5‐methyl‐1,3,4‐thiadiazol‐2‐amine and pyridine‐2,3‐dicarboxylate

The bifunctional pyridine‐2,3‐dicarboxylic acid (H₂pdc) ligand has one N atom and four O atoms, which could bind more than one Ag^I centre with diverse binding modes. A novel infinite one‐dimensional Ag^I coordination polymer, namely catena‐poly[[silver(I)‐(μ₂‐pyridine‐2,3‐dicarboxylato‐κ²N :O ³)‐silver(I)‐tris(μ₂‐5‐methyl‐1,3,4‐thiodiazol‐2‐amine‐κ²N :N ′)] monohydrate ethanol monosolvate], {[Ag₂(C₇H₃NO₄)(C₃H₅N₃S)₃]·H₂O·C₂H₅OH}_n , has been synthesized using H₂pdc and 5‐methyl‐1,3,4‐thiadiazol‐2‐amine (tda), and characterized by single‐crystal X‐ray diffraction. One Ag^I atom is located in a four‐coordinated AgN₄ tetrahedral geometry and the other Ag^I atom is in a tetrahedral AgN₃O geometry. A dinuclear Ag^I cluster formed by three tda ligands with a paddelwheel configuration is bridged by the dianionic pdc²⁻ ligand into a one‐dimensional coordination polymer. Interchain N—H…O hydrogen bonds extend the one‐dimensional chains into an undulating two‐dimensional sheet. The sheets are further packed into a three‐dimensional supramolecular framework by interchain N—H…O hydrogen bonds.     

A two‐dimensional undulating AgI coordination polymer constructed of Ag—C and Ag—O bonds: poly[[[μ3‐(5,6‐η):κO2:κO2‐(±)‐(1S,2S,3R,4R)‐3‐carboxy‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2‐carboxylato]silver(I)] monohydrate]

The title coordination polymer, {[Ag(C₈H₇O₅)]·H₂O}_n, is built from Ag⁺ cations and singly protonated dehydronorcantharidin (SP‐DNC) anions, with a distorted trigonal‐planar geometry at the metal centre. The coordination number of Ag^I is three (with one Ag—π bond and two Ag—O bonds, one from each of three different SP‐DNC ligands), if only formal Ag–ligand bonds are considered, but can be regarded as five if longer weak Ag...O interactions are also included. The two‐dimensional corrugated‐sheet coordination polymer forms a non‐interpenetrating framework with (4.8²) topology. Disordered water molecules are sandwiched between the sheets.     

Poly[(N,N‐dimethylformamide‐κO)(μ3‐4,4′‐ethylenedibenzoato‐κ5O,O′:O′:O′′,O′′′)(pyrazino[2,3‐f][1,10]phenanthroline‐κ2N8,N9)lead(II)]

In the title Pb^II coordination polymer, [Pb(C₁₆H₁₀O₄)(C₁₄H₈N₄)(C₃H₇NO)]_n, each Pb^II atom is eight‐coordinated by two chelating N atoms from one pyrazino[2,3‐f][1,10]phenanthroline (L) ligand, one dimethylformamide (DMF) O atom and five carboxylate O atoms from three different 4,4′‐ethylenedibenzoate (eedb) ligands. The eedb dianions bridge neighbouring Pb^II centres through four typical Pb—O bonds and one longer Pb—O interaction to form a two‐dimensional structure. The C atoms from the L and eedb ligands form C—H...O hydrogen bonds with the O atoms of eedb and DMF ligands, which further stabilize the structure. The title compound is the first Pb^II coordination polymer incorporating the L ligand.     

A sulfur coordination polymer with wide bandgap semiconductivity formed from zinc(II) and 5‐methylsulfanyl‐1,3,4‐thiadiazole‐2‐thione

The sulfur coordination polymer catena‐poly[zinc(II)‐μ₂‐bis[5‐(methylsulfanyl)‐2‐sulfanylidene‐2,3‐dihydro‐1,3,4‐thiadiazol‐3‐ido‐κ²N³:S]], [Zn(C₃H₃N₂S₃)₂]_n or [Zn₂MTT₄]_n, constructed from Zn²⁺ ions and 5‐methylsulfanyl‐1,3,4‐thiadiazole‐2‐thione (HMTT), was synthesized successfully and structurally characterized. [Zn₂MTT₄]_n crystallizes in the tetragonal space group I (No. 82). Each MTT^? ligand (systematic name: 5‐methylsulfanyl‐2‐sulfanylidene‐2,3‐dihydro‐1,3,4‐thiadiazol‐3‐ide) coordinates to two different Zn^II ions, one via the thione group and the other via a ring N atom, with one Zn^II atom being in a tetrahedral ZnS₄ and the other in a tetrahedral ZnN₄ coordination environment. These tetrahedral ZnS₄ and ZnN₄ units are alternately linked by the organic ligands, forming a one‐dimensional chain structure along the c axis. The one‐dimensional chains are further linked via C—H…N and C—H…S hydrogen bonds to form a three‐dimensional network adopting an ABAB‐style arrangement that lies along both the a and b axes. The three‐dimensional Hirshfeld surface analysis and two‐dimensional (2D) fingerprint plots confirm the major interactions as C—H…S hydrogen bonds with a total of 35.1%, while 7.4% are C—H…N hydrogen‐bond interactions. [Zn₂MTT₄]_n possesses high thermal and chemical stability and a linear temperature dependence of the bandgap from room temperature to 270 °C. Further investigation revealed that the bandgap changes sharply in ammonia, but only fluctuates slightly in other solvents, indicating its promising application as a selective sensor.     

Quercetin 2,4‐Dioxygenase Activates Dioxygen in a Side‐On O2–Ni Complex

Quercetin 2,4‐dioxygenase (quercetinase) from Streptomyces uses nickel as the active‐site cofactor to catalyze oxidative cleavage of the flavonol quercetin. How this unusual active‐site metal supports catalysis and O₂ activation is under debate. We present crystal structures of Ni‐quercetinase in three different states, thus providing direct insight into how quercetin and O₂ are activated at the Ni²⁺ ion. The Ni²⁺ ion is coordinated by three histidine residues and a glutamate residue (E⁷⁶) in all three states. Upon binding, quercetin replaces one water ligand at Ni and is stabilized by a short hydrogen bond through E⁷⁶, the carboxylate group of which rotates by 90°. This conformational change weakens the interaction between Ni and the remaining water ligand, thereby preparing a coordination site at Ni to bind O₂. O₂ binds side‐on to the Ni²⁺ ion and is perpendicular to the C2?C3 and C3?C4 bonds of quercetin, which are cleaved in the following reaction steps.     

Three structures containing (E)‐1,2‐bis­(benzimidazol‐2‐yl)ethene groups

Two of the title compounds, namely (E)‐1,2‐bis­(1‐methyl­benzimidazol‐2‐yl)ethene, C₁₈H₁₆N₄, (Ib), and (E)‐1,2‐bis­(1‐ethyl­benzimidazol‐2‐yl)ethene, C₂₀H₂₀N₄, (Ic), consist of centrosymmetric trans‐bis­(1‐alkyl­benzimidazol‐2‐yl)ethene mol­ecules, while 3‐eth­yl‐2‐[(E)‐2‐(1‐ethyl­benzimidazol‐2‐yl)­ethen­yl]benzimidazol‐1‐ium perchlorate, C₂₀H₂₁N₄⁺·ClO₄⁻, (II), contains the monoprotonated analogue of compound (Ic). In the three structures, the benzimidazole and benzimidazolium moieties are essentially planar; the geometric parameters for the ethene linkages and their bonds to the aromatic groups are consistent with double and single bonds, respectively, implying little, if any, conjugation of the central C=C bonds with the nitro­gen‐containing rings. The C—N bond lengths in the N=C—N part of the benzimidazole groups differ and are consistent with localized imine C=N and amine C—N linkages in (Ib) and (Ic); in contrast, the corresponding distances in the benzimidazolium cation are equal in (II), consistent with electron delocalization resulting from protonation of the amine N atom. Crystals of (Ib) and (Ic) contain columns of parallel mol­ecules, which are linked by edge‐over‐edge C—H⋯π overlap. The columns are linked to one another by C—H⋯π inter­actions and, in the case of (Ib), C—H⋯N hydrogen bonds. Crystals of (II) contain layers of monocations linked by π–π inter­actions and separated by both perchlorate anions and the protruding eth­yl groups; the cations and anions are linked by N—H⋯O hydrogen bonds.     

N−N Bond Forming Reductive Elimination via a Mixed‐Valent Nickel(II)–Nickel(III) Intermediate

Natural products containing N–N bonds exhibit important biological activity. Current methods for constructing N?N bonds have limited scope. An advanced understanding of the fundamental N?N bond formation/cleavage processes occurring at the transition‐metal center would facilitate the development of catalytic reactions. Herein we present an N?N bond‐forming reductive elimination, which proceeds via a mixed‐valent Ni^II–Ni^III intermediate with a Ni–Ni bond order of zero. The discrete Ni^II–Ni^III oxidation states contrast with the cationic dimeric Ni analogue, in which both Ni centers are equivalent with an oxidation state of 2.5. The electronic structures of these mixed‐valent complexes have implications for the fundamental understanding of metal–metal bonding interactions.     

catena‐Poly­[[(di‐2‐pyridyl­amine)­silver(I)]‐μ‐nicotinato] and catena‐poly­[[(di‐2‐pyridyl­amine)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato]

In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐nico­tinato‐κ²N:O], [Ag(C₆H₄NO₂)(C₁₀H₉N₃)]_n, the Ag^I atom is tetracoordinated by two N atoms from the di‐2‐pyridyl­amine (BPA) ligand [Ag—N = 2.3785 (18) and 2.3298 (18) Å] and by one N atom and one carboxyl­ate O atom from nicotinate ligands [Ag—N = 2.2827 (15) Å and Ag—O = 2.3636 (14) Å]. Bridging by nicotinate N and O atoms generates a polymeric chain structure, which extends along [100]. The carboxyl O atom not bonded to the Ag atom takes part in an intrachain C—H⋯O hydrogen bond, further stabilizing the chain. Pairs of chains are linked by N—H⋯O hydrogen bonds to generate ribbons. There are no π–π interactions in this complex. In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato‐κ²O¹:O²], [Ag(C₇H₅O₄)(C₁₀H₉N₃)]_n, the Ag^I atom has a distorted tetrahedral coordination, with three strong bonds to two pyridine N atoms from the BPA ligand [Ag—N = 2.286 (5) and 2.320 (5) Å] and to one carboxyl­ate O atom from the 2,6‐di­hydroxy­benzoate ligand [Ag—O = 2.222 (4) Å]; the fourth, weaker, Ag‐atom coordination is to one of the phenol O atoms [Ag⋯O = 2.703 (4) Å] of an adjacent moiety, and this interaction generates a polymeric chain along [100]. Pairs of chains are linked about inversion centers by N—H⋯O hydrogen bonds to form ribbons, within which there are π–π interactions. The ribbons are linked about inversion centers by pairs of C—H⋯O hydrogen bonds and additional π–π interactions between inversion‐related pairs of 2,6‐di­hydroxy­benzoate ligands to generate a three‐dimensional network.     

An unusual coordination polymer containing Cu+ ions and featuring possible Cu...Cu `cuprophilic' interactions: poly[di‐μ‐chlorido‐(μ4‐3,5‐diaminobenzoato‐κ4O:O′:N:N′)tricopper(I)(3 Cu—Cu)]

Compounds containing copper(I) are of interest for their role in biological processes. The nature of short (< ∼3.2 Å) Cu...Cu contacts within these compounds has been debated, being either described as weakly attractive (bonding) `cuprophilic' interactions, or simply as short metal–metal distances constrained by ligand geometry or largely ionic in nature. The title three‐dimensional Cu<sup>+</sup>‐containing coordination polymer, [Cu<sub>3</sub>(C<sub>7</sub>H<sub>7</sub>N<sub>2</sub>O<sub>2</sub>)Cl<sub>2</sub>]<sub>n</sub>, was formed from the in situ reduction of CuCl<sub>2</sub> in the presence of 3,5‐diaminobenzoic acid and KOH under hydrothermal conditions. Its complex crystal structure contains ten distinct Cu<sup>I</sup> atoms, two of which lie on crystallographic inversion centres. The copper coordination geometries include near‐linear CuOCl and CuN<sub>2</sub>, T‐shaped CuOCl<sub>2</sub> and distorted tetrahedral CuOCl<sub>3</sub> groups. Each Cu<sup>I</sup> atom is also associated with two adjacent metal atoms, with Cu...Cu distances varying from 2.7350 (14) to 3.2142 (13) Å; if all these are regarded as `cuprophilic' interactions, then infinite [01] zigzag chains of Cu^I atoms occur in the crystal. The structure is consolidated by N—H...Cl hydrogen bonds.     

A T‐Shaped Nickel(I) Metalloradical Species

A T‐shaped Ni^I complex was synthesized using a rigid acridane‐based pincer ligand to prepare a metalloradical center. Structural data displays a nickel ion is embedded in the plane of a PNP ligand. Having a sterically exposed half‐filled orbital, this three‐coordinate Ni^I species reveals unique open‐shell reactivity including the homolytic cleavage of various σ‐bonds, such as H−H, N−N, and C−C.     

Oxidation State Dependent Coordination Modes: Accessing an Amidate‐Supported Nickel(I) δ‐bis(C−H) Agostic Complex

Amidate‐supported two‐ and three‐coordinate Ni^I complexes were synthesized by reduction of the corresponding Ni^II precursors. A dramatic change in binding mode is observed upon reduction from Ni^II to Ni^I. The Ni^I derivatives include an unprecedented Ni^I bis(C?H) agostic complex and a two‐coordinate Ni^I complex.     

In situ single‐crystal to single‐crystal (SCSC) transformation of the one‐dimensional polymer catena‐poly[[diaqua(sulfato)copper(II)]‐μ2‐glycine] into the two‐dimensional polymer poly[μ2‐glycine‐μ4‐sulfato‐copper(II)]

The one‐dimensional coordination polymer catena‐poly[diaqua(sulfato‐κO)copper(II)]‐μ₂‐glycine‐κ²O:O′], [Cu(SO₄)(C₂H₅NO₂)(H₂O)₂]_n, (I), was synthesized by slow evaporation under vacuum of a saturated aqueous equimolar mixture of copper(II) sulfate and glycine. On heating the same blue crystal of this complex to 435 K in an oven, its aspect changed to a very pale blue and crystal structure analysis indicated that it had transformed into the two‐dimensional coordination polymer poly[(μ₂‐glycine‐κ²O:O′)(μ₄‐sulfato‐κ⁴O:O′:O′′:O′′)copper(II)], [Cu(SO₄)(C₂H₅NO₂)]_n, (II). In (I), the Cu^II cation has a pentacoordinate square‐pyramidal coordination environment. It is coordinated by two water molecules and two O atoms of bridging glycine carboxylate groups in the basal plane, and by a sulfate O atom in the apical position. In complex (II), the Cu^II cation has an octahedral coordination environment. It is coordinated by four sulfate O atoms, one of which bridges two Cu^II cations, and two O atoms of bridging glycine carboxylate groups. In the crystal structure of (I), the one‐dimensional polymers, extending along [001], are linked via N—H...O, O—H...O and bifurcated N—H...O,O hydrogen bonds, forming a three‐dimensional framework. In the crystal structure of (II), the two‐dimensional networks are linked via bifurcated N—H...O,O hydrogen bonds involving the sulfate O atoms, forming a three‐dimensional framework. In the crystal structures of both compounds, there are C—H...O hydrogen bonds present, which reinforce the three‐dimensional frameworks.     

A stair‐like two‐dimensional silver(I) coordination polymer of N′‐(3‐cyanobenzylidene)nicotinohydrazide

The structure of the title compound, poly[[[μ₃‐N′‐(3‐cyanobenzylidene)nicotinohydrazide]silver(I)] hexafluoroarsenate], {[Ag(C₁₄H₁₀N₄O)](AsF₆)}_n, at 173 K exhibits a novel stair‐like two‐dimensional layer and a three‐dimensional supramolecular framework through C—H...Ag hydrogen bonds. The Ag^I cation is coordinated by three N atoms and one O atom from N′‐(3‐cyanobenzylidene)nicotinohydrazide (L) ligands, resulting in a distorted tetrahedral coordination geometry. The organic ligand acts as a μ₃‐bridging ligand through the pyridyl and carbonitrile N atoms and deviates from planarity in order to adapt to the coordination geometry. Two ligands bridge two Ag^I cations to construct a small 2+2 Ag₂L₂ ring. Four ligands bridge one Ag^I cation from each of four of these small rings to form a large grid. An interesting stair‐like two‐dimensional (3,6)‐net is formed through Ag^I metal centres acting as three‐connection nodes and through L molecules as tri‐linkage spacers.     

Two novel silver(I) coordination polymers: poly[(μ2‐2‐aminopyrimidine‐κ2N1:N3)bis(μ3‐thiocyanato‐κ3S:S:S)disilver(I)] and poly[(2‐amino‐4,6‐dimethylpyrimidine‐κN)(μ3‐thiocyanato‐κ3N:S:S)silver(I)]

2‐Aminopyrimidine (L1) and 2‐amino‐4,6‐dimethylpyrimidine (L2) have been used to create the two novel title complexes, [Ag₂(NCS)₂(C₄H₅N₃)]_n, (I), and [Ag(NCS)(C₆H₉N₃)]_n, (II). The structures of complexes (I) and (II) are mainly directed by the steric properties of the ligands. In (I), the L1 ligand is bisected by a twofold rotation axis running through the amine N atom and opposite C atoms of the pyrimidine ring. The thiocyanate anion adopts the rare μ₃‐κ³S coordination mode to link three tetrahedrally coordinated Ag^I ions into a two‐dimensional honeycomb‐like 6³ net. The L1 ligands further extend the two‐dimensional sheet to form a three‐dimensional framework by bridging Ag^I ions in adjacent layers. In (II), with three formula units in the asymmetric unit, the L2 ligand bonds to a single Ag^I ion in a monodentate fashion, while the thiocyanate anions adopt a μ₃‐κ¹N,κ²S coordination mode to link the AgL2 subunits to form two‐dimensional sheets. These layers are linked by N—H...N hydrogen bonds between the noncoordinated amino H atoms and both thiocyanate and pyrimidine N atoms.