Structural characterization of silver dialkylphosphite salts using solid‐state 109Ag and 31P NMR spectroscopy,IR spectroscopy and DFT calculations

High‐resolution solid‐state ¹⁰⁹Ag and ³¹P NMR spectroscopy was used to investigate a series of silver dialkylphosphite salts, Ag(O)P(OR)₂ (R = CH₃, C₂H₅, C₄H₉ and C₈H₁₇), and determine whether they adopt keto, enol or dimer structures in the solid state. The silver chemical shift, CS, tensors and |J(¹⁰⁹Ag, ³¹P)| values for these salts were determined using ¹⁰⁹Ag (Ξ = 4.652%) NMR spectroscopy. The magnitudes of J(¹⁰⁹Ag, ³¹P) range from 1250 ± 10 to 1318 ± 10 Hz and are the largest reported so far. These values indicate that phosphorus is directly bonded to silver for all these salts and thus exclude the enol structure. All ³¹P NMR spectra exhibit splittings due to indirect spin–spin coupling to ¹⁰⁷Ag (I = 1/2, NA = 51.8%) and ¹⁰⁹Ag (I = 1/2, NA = 48.2%). The ¹J(¹⁰⁹Ag, ³¹P) values measured by both ¹⁰⁹Ag and ³¹P NMR spectroscopy agree within experimental error. Analysis of ³¹P NMR spectra of stationary samples for these salts allowed the determination of the phosphorus CS tensors. The absence of characteristic P?O stretching absorption bands near 1250 cm^?1 in the IR spectra for these salts exclude the simple keto tautomer. Thus, the combination of solid‐state NMR and IR results indicate that these silver dialkylphosphite salts probably have a dimer structure. Values of silver and phosphorus CS tensors as well as ¹J(¹⁰⁹Ag, ³¹P) values for a dimer model calculated using the density functional theory (DFT) method are in agreement with the experimental observations. Copyright © 2010 John Wiley & Sons, Ltd.     

NHC Supersilyl Silver Complex [Ag(IPr)SitBu3] as a Promising Agent for Substitution Reactions

The NHC supersilyl silver complex [Ag(IPr)SitBu₃] (IPr = NHC_IPr) was prepared by treatment of Ag(IPr)Cl with Na(thf)₂[SitBu₃] in benzene/thf at room temperature. X-ray quality crystals of the NHC supersilyl silver complex [Ag(IPr)SitBu₃] (monoclinic, space group P2₁/m) were grown from heptane at room temperature. The ²⁹Si NMR spectrum of a solution of [Ag(IPr)SitBu₃] in C₆D₆ revealed two doublets caused by coupling to ¹⁰⁷Ag and ¹⁰⁹Ag nuclei. We further investigated the possibility of a conversion of triel halides EX₃ by treatment with [Ag(IPr)SitBu₃]. At ambient temperature the reaction of [Ag(IPr)SitBu₃] with an excess of EX₃ yielded tBu₃SiEX₂ (E = B, Al; X = Cl, Br; E = Ga; X = Cl) and IPr · EX₃ (EX₃ = BCl₃, BBr₃, AlCl₃, AlBr₃, GaCl₃). The identity of tBu₃SiEX₂ and IPr · EX₃ was confirmed by comparison with authentic samples.     

N‐Phenyl‐substituted carbene precursors and their silver complexes: synthesis,characterization and antimicrobial activities

A series of unsymmetrically substituted N‐heterocyclic carbene (NHC) precursors ( 1a , 1b , 1c , 1d , 1e ) were synthesized from the reaction of N‐phenylbenzimidazole with various alkyl halides. These compounds were used to synthesize NHC–silver(I) complexes ( 2a , 2b , 2c , 2d , 2e ). The five new 1‐phenyl‐3‐alkylbenzimidazolium salts ( 1a , 1b , 1c , 1d , 1e ) and their NHC–silver complexes ( 2a , 2b , 2c , 2d , 2e ) were characterized by the ¹H NMR, ¹³C NMR and FT‐IR spectroscopic methods and elemental analysis techniques. Also, the two NHC–silver complexes 2b and 2c were characterized by single‐crystal X‐ray crystallography, which confirmed the linear C―Ag―Cl arrangements. The antibacterial activities of the NHC precursor and NHC–silver complexes were tested against three Gram‐positive bacterial strains (Bacillus subtilis, Listeria monocytogenes and Staphylococcus aureus) and three Gram‐negative bacterial strains (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa) using the microdilution broth method. The NHC–silver complexes showed higher antibacterial activity than the NHC precursors. In addition, silver complexes 2a , 2b , 2c , 2d showed high antibacterial activity against the Gram‐positive bacteria L. monocytogenes and S. aureus compared to the standard, tetracycline. Copyright © 2014 John Wiley & Sons, Ltd.     

Structure Determination of an AgI‐Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1H/15N/109Ag NMR Spectroscopy

The structure of an Ag^I‐mediated cytosine–cytosine base pair, C–Ag^I–C, was determined with NMR spectroscopy in solution. The observation of 1‐bond ¹⁵N‐¹⁰⁹Ag J‐coupling (¹J(¹⁵N,¹⁰⁹Ag): 83 and 84 Hz) recorded within the C–Ag^I–C base pair evidenced the N3–Ag^I–N3 linkage in C–Ag^I–C. The triplet resonances of the N4 atoms in C–Ag^I–C demonstrated that each exocyclic N4 atom exists as an amino group (?NH₂), and any isomerization and/or N4–Ag^I bonding can be excluded. The 3D structure of Ag^I–DNA complex determined with NOEs was classified as a B‐form conformation with a notable propeller twist of C–Ag^I–C (?18.3±3.0°). The ¹⁰⁹Ag NMR chemical shift of C‐Ag^I‐C was recorded for cytidine/Ag^I complex (δ(¹⁰⁹Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C–Ag^I–C base pair.     

Solid-state 31P and 109Ag CP/MAS NMR as a powerful tool for studying of silver(I) complexes with N-thiophosphorylated thiourea and thioamide ligands

A family of three- and four-coordinated silver(I) complexes of formulas [Ag(PPh₃)₂L], [Ag(PPh₃)L], and [AgL]_n with N-thiophosphorylated thiourea and thioamide ligands of general formula RC(S)NHP(S)(OPri)₂ [R = Ph, PhNH, iPrNH, tBuNH, NH₂] have been studied by solid-state ¹⁰⁹Ag and ³¹P CPMAS NMR spectroscopy. ¹⁰⁹Ag NMR spectra have provided valuable structural information about Ag coordination, which is in good accordance with the available crystal structure data. The data presented in this work represent a significant addition to the available ¹⁰⁹Ag chemical shifts and chemical shifts anisotropies. The silver chemical shift ranges for different P,S-environments and coordination state were discussed in detail. The ¹J(³¹P–^107/109Ag) and ²J(³¹P–³¹P) values were determined and analyzed.     

Synthesis,Characterization and Biological Evaluation of Two Silver(I) trans‐Cinnamate Complexes as Urease Inhibitors

Two new silver(I) trans‐cinnamates, namely [Ag(2‐cca)(H₂O)]₂ ( 1 ) and [Ag(4‐cca)]_n ( 2 ) (2‐ccaH = 2‐chlorocinnamic acid and 4‐ccaH = 4‐chlorocinnamic acid), were synthesized and structurally characterized. Single crystal X‐ray studies reveal that each silver(I) atom in 1 is two‐coordinate by a 2‐chlorocinnamate ligand and one water molecule to afford a discrete centrosymmetric dimer with the ligand‐unsupported Ag···Ag interactions (3.218(4) Å), while a pair of symmetry‐related silver(I) atoms in 2 are clamped by two μ₂‐η¹:η¹ 4‐chlorocinnamate ligands to yield a binuclear silver(I) moiety incorporating a ligand‐supported Ag···Ag interaction (2.819(5) Å). Both complexes 1 and 2 show potent urease inhibitory activities with the respective IC₅₀ values of 0.66 and 1.10 μM.     

Copper and Silver Carbene Complexes without Heteroatom‐Stabilization: Structure,Spectroscopy, and Relativistic Effects

Salts of a copper and a silver carbene complex were prepared from dimesityl diazomethane, made possible by the steric shielding of the N‐heterocyclic carbene (NHC) ancillary ligand IPr**. The mint‐green complex [IPr**Ag=CMes₂]⁺[NTf₂]^? is the first isolated silver carbene complex without heteroatom donor substituents. Single‐crystal X‐ray diffraction provides evidence for a predominant carbenoid character, and supports the postulation of such reactive species as intermediates in silver‐catalyzed C? H activation reactions. The greenish yellow copper carbene complex [IPr**Cu=CMes₂]⁺[NTf₂]^? has spectroscopic properties in between the isostructural silver complex and the already reported emerald green gold carbene complex. A comparison in the Group 11 series indicates that relativistic effects are responsible for the strong σ bond and the significant π back‐bonding in the gold carbene moiety.     

Binuclear meta‐xylyl‐linked Ag(I)‐N‐heterocyclic carbene complexes of N‐alkyl/aryl‐alkyl‐substituted bis‐benzimidazolium salts: synthesis,crystal structures and in vitro anticancer studies

Salts of meta‐xylyl‐linked N‐ethyl/n‐butyl/benzyl‐substituted bis‐benzimidazolium having hexafluorophosphate counterions have been synthesized. The corresponding binuclear Ag(I)‐N‐heterocyclic carbene complexes were prepared by the reaction of Ag₂O. The N‐heterocyclic carbene (NHC) ligand precursor 7 and Ag(I)–NHC complexes 10 and 11 have been structurally characterized by single‐crystal X‐ray diffraction technique. All of the reported compounds have been tested for their anticancer activity using human colorectal (HCT 116) cancer cell lines. Sterically varied benzimidazolium salts displayed significant activity against HCT 116 cell line, yielding IC₅₀ values in the range 0.1–19.4 µ m , while Ag(I)–carbene complexes showed exceptionally good activity (0.2–1.3 µ m ) against tested cancer cell lines. Copyright © 2013 John Wiley & Sons, Ltd.     

N‐Heterocyclic Carbene‐Protected Ag Nanoparticles Immobilized on Polyacrylonitrile Fiber as Efficient Catalysts for a Three‐Component Coupling Reaction

Metal nanoparticles (NPs) are routinely stabilized by the introduction of capping agents or their distribution on supports. In this context, we report the preparation and characterization of N‐heterocyclic carbene (NHC)‐stabilized silver NPs supported on polyacrylonitrile fiber (PANF). As a result, Ag loadings of up to 8 % and particle sizes of 11.0±3.2 nm were achieved. This novel nanocomposite catalyst demonstrated high activity in addition to excellent stability and reusability in the three‐component reaction between alkynes, haloalkanes, and amines. In this system, the AgNPs were stabilized by both a support effect and a ligand effect. The unique NHC‐protected AgNP structure and the PANF support provide a synergistic effect in the deprotonation of C_sp?H bonds, with turnover numbers of up to 3500. This catalyst was successfully recycled over eight runs without any significant loss in activity, and with no significant aggregation of the AgNPs. Moreover, implementation of a flow system with PANF‐NHC@Ag as catalyst leads to an efficient productivity of 57 mmol h^?1.     

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.     

Selective J‐resolved‐HMQC‐1 and ‐2, new methods for measuring proton–proton coupling constants in strongly coupled spin systems

Efficient pulse sequences for measuring ¹H–¹H coupling constants (J_HH) in strongly coupled spin systems, named selective J‐resolved‐HMQC‐1 and ‐2, have been developed. In the strongly coupled spin systems such as ‐CH₂‐CH_A(OH)‐CH_B(OH)‐CH₂‐, measurements of ³J_HAHB are generally difficult owing to the complicated splitting caused by the adjacent CH₂ protons. For easier and accurate measurements of ³J_HAHB in such a spin system, a selective excitation pulse is incorporated into the J‐resolved HMQC pulse sequence. In the proposed methods, only two strongly coupled protons, H_A and H_B which are excited by a selective pulse, are observed as J‐resolved HMQC signals. The cross peaks of H_A and H_B appear as doublets owing to ³J_HAHB along the F₁ dimension in the selective J‐resolved HMQC‐1 and ‐2 experiments. The efficiency of the proposed pulse sequences has been demonstrated in application to the stereochemical studies of the complicated natural product, monazomycin. Copyright © 2011 John Wiley & Sons, Ltd.     

187Os subspectra in 1H and 31P{1H} spectra of triosmium carbonyl clusters

A survey of the use of ¹⁸⁷Os satellite subspectra in ¹H and ³¹P{¹H} spectra of triosmium carbonyl clusters is reported. By varying evolution delays in HMQC spectra of [Os₃(µ‐H)₂(CO)₁₀] we have selectively extracted the values for ¹J(Os,H) and ²J(Os,H), respectively. An analysis of the principal modes of phosphine coordination in triosmium clusters demonstrates that ³¹P{¹H}¹⁸⁷Os satellite subspectra are diagnostic for equatorial coordination [¹J(Os,P) = 211–223 Hz] or for axial coordination (perpendicular to the plane of the cluster) [¹J(Os,P) ≈ 147 Hz]. Chelating and bridging diphosphines yield ¹⁸⁷Os satellite subspectra which are the sum of A₂X and AA′X spin systems. If significant P–P coupling is present, the AA′X component requires simulation. All observed ²J(Os,P) trans‐equatorial couplings fall in the range 38–65 Hz. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis,cytotoxicity and antibacterial studies of symmetrically and non‐symmetrically benzyl‐ or p‐cyanobenzyl‐substituted N‐Heterocyclic carbene–silver complexes

From the reaction of 1H‐imidazole ( 1a ), 4,5‐dichloro‐1H‐imidazole ( 1b ) and 1H‐benzimidazole ( 1c ) with p‐cyanobenzyl bromide ( 2 ), symmetrically substituted N‐heterocyclic carbene (NHC) [( 3a–c )] precursors, 1‐methylimidazole ( 5a ), 4,5‐dichloro‐1‐methylimidazole ( 5b ) and 1‐methylbenzimidazole ( 5c ) with benzyl bromide ( 6 ), non‐symmetrically substituted N‐heterocyclic carbene (NHC) [( 7a–c )] precursors were synthesized. These NHC? precursors were then reacted with silver(I) acetate to yield the NHC‐silver complexes [1,3‐bis(4‐cyanobenzyl)imidazole‐2‐ylidene] silver(I) acetate ( 4a ), [4,5‐dichloro‐1,3‐bis(4‐cyanobenzyl)imidazole‐2‐ylidene] silver(I) acetate ( 4b ), [1,3‐bis(4‐cyanobenzyl)benzimidazole‐2‐ylidene] silver(I) acetate ( 4c ), (1‐methyl‐3‐benzylimidazole‐2‐ylidene) silver(I) acetate ( 8a ), (4,5‐dichloro‐1‐methyl‐3‐benzylimidazole‐2‐ylidene) silver(I) acetate ( 8b ) and (1‐methyl‐3‐benzylbenzimidazole‐2‐ylidene) silver(I) acetate ( 8c ) respectively. The four NHC‐precursors 3a–c, 7c and four NHC–silver complexes 4a–c and 8c were characterized by single crystal X‐ray diffraction. The preliminary antibacterial activity of all the compounds was studied against Gram‐negative bacteria Escherichia coli, and Gram‐positive bacteria Staphylococcus aureus using the qualitative Kirby‐Bauer disc‐diffusion method. All NHC–silver complexes exhibited medium to high antibacterial activity with areas of clearance ranging from 4 to 12 mm at the highest amount used, while the NHC‐precursors showed significantly lower activity. In addition, all NHC–silver complexes underwent preliminary cytotoxicity tests on the human renal‐cancer cell line Caki‐1 and showed medium to high cytotoxicity with IC₅₀ values ranging from 53 ( ± 8) to 3.2 ( ± 0.6) µM. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,Characterization, and Luminescent Properties of Silver(I) Complexes based on Diphosphine Ligands and 2,9‐Dimethyl‐1,10‐phenanthroline

Five mono‐nuclear silver(I) complexes with the ligand 2,9‐dimethyl‐1,10‐phenanthroline, namely [Ag(DPEphos)(dmp)]BF₄ ( 1 ), [Ag(DPEphos)(dmp)]CF₃SO₃ ( 2 ), [Ag(DPEphos)(dmp)]ClO₄ ( 3 ), [Ag(DPEphos)(dmp)]NO₃ ( 4 ), and [Ag(dppb)(dmp)]NO₃ · CH₃OH ( 5 ) {DPEphos = bis[2‐(diphenylphosphanyl)phenyl]ether, dppb = 1,2‐bis(diphenylphosphanyl)benzene, dmp = 2,9‐dimethyl‐1,10‐phenanthroline} were characterized by X‐ray diffraction, IR, ¹H NMR, ³¹P NMR and fluorescence spectroscopy. Their terahertz (THz) time‐domain spectra were also studied. In these complexes the silver(I), which is coordinated by two kinds of chelating ligands, adopts four‐coordinate modes to generate mono‐nuclear structures. In complexes 1 , 3 – 5 , offset π ··· π weak interactions exist between the neighboring benzene rings. In the ³¹P NMR spectra, there exist splitting signals (dd), which can be attributed to the coupling of the ^107,109Ag–³¹P. All the emission peaks of these complexes are attributed to ligand‐centered excited states.     

Dinuclear rectangular-shaped assemblies of bis-benzimidazolydine salt coordinated to Ag(I) and Cu(I) <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbene complexes and their biological applications

A benzimidazolydine-based novel ligand L2 was prepared from 1,2-bis(benzimidazol-1-yl)ethane (L1) and synthesis of metallocycle complexes such as Ag(I)–N-Heterocyclic Carbene abbreviated as Ag–NHC and Cu(I)–N-Heterocyclic Carbene complex as Cu–NHC were synthesized and then estimated for antimicrobial and antioxidant properties. Synthesis of Ag–NHC and Cu–NHC metallocycle complexes was described. The benzimidazolydine ligand precursor and its Ag–NHC and Cu–NHC were successfully characterized by FT-IR, FT-Raman, 1D and 2D NMR, HR-ESI mass spectra, and cyclic voltammetric studies. In the present work, antimicrobial study discloses that ligand (L1 and L2) do not show inhibitory activity against various pathogens; however, it was gradually increased, when they were coordinated to metals like Ag and Cu. Among the four compounds, the Ag–NHC strongly hampers the growth of fungal strains. The minimal inhibitory concentration (MIC) ranged between 46 and 750 μg mL^?1. A distinctive cell growth reduction was observed in C. albicans when treated with minimum concentration of Ag–NHC complex. Ag–NHC exhibited the ability to prevent the growth of C. albicans by causing severe membrane damage and accumulation of intracellular reactive oxygen species (ROS), which were revealed by fluorescence spectroscopic studies. The tested (L1, L2, Ag–NHC and Cu–NHC) compounds demonstrated significant activity with IC₅₀ values range (0.20–30 μM) for DPPH, OH and NO antioxidant activity. Ascorbic acid was used as standard drug. The radical scavenging potencies of the compounds were explored by employing DPPH, OH and NO assays, in which Ag–NHC exhibited highest inhibitory effect on the radicals [IC₅₀?=?57.3 μM (DPPH), 57.7 μM (OH), 52.3 μM (NO)].     

Synthesis,crystal structure and studies on the interaction with albumin of a new silver(I) complex based on 2‐(4‐nitrobenzenesulfonamido)benzoic acid

In the present work, the two‐dimensional (2D) polymer poly[[μ₄‐2‐(4‐nitrobenzenesulfonamido)benzoato‐κ⁴O¹:O¹:O^1′:N⁶]silver(I)] (AgL), [Ag(C₁₃H₉N₂O₆S)]_n, was obtained from 2‐(4‐nitrobenzenesulfonamido)benzoic acid (HL), C₁₃H₁₀N₂O₆S. FT–IR, ¹H and ¹³C{¹H} NMR spectroscopic analyses were used to characterize both compounds. The crystal structures of HL and AgL were determined by single‐crystal X‐ray diffraction. In the structure of HL, O—H…O hydrogen bonds between neighbouring molecules result in the formation of dimers, while the silver(I) complex shows polymerization associated with the O atoms of three distinct deprotonated ligands (L^?). Thus, the structure of the Ag complex can be considered as a coordination polymer consisting of a one‐dimensional linear chain, constructed by carboxylate bridging groups, running parallel to the b axis. Neighbouring polymeric chains are further bridged by Ag—C monohapto contacts, resulting in a 2D framework. Fingerprint analysis of the Hirshfeld surfaces show that O…H/H…O hydrogen bonds are responsible for the most significant contacts in the crystal packing of HL and AgL, followed by the H…H and O…C/C…O interactions. The Ag…Ag, Ag…O/O…Ag and Ag…C/C…Ag interactions in the Hirshfeld surface represent 12.1% of the total interactions in the crystal packing. Studies of the interactions of the compounds with human serum albumin (HSA) indicated that both HL and AgL interact with HSA.     

Nitridorhenium(V) Complexes with 1,3,4‐Triphenyl‐1,2,4‐triazol‐5‐ylidene

[ReNCl₂(PPh₃)₂] and [ReNCl₂(PMe₂Ph)₃] react with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (HL^Ph) under formation of the stable rhenium(V) nitrido complex [ReNCl(HL^Ph)(L^Ph)], which contains one of the two NHC ligands with an additional orthometallation. The rhenium atom in the product is five‐coordinate with a distorted square‐pyramidal coordination sphere. The position trans to the nitrido ligand is blocked by one phenyl ring of the monodentate HL^Ph ligand. The Re–C(carbene) bond lengths of 2.072(6) and 2.074(6) Å are comparably long and indicate mainly σ‐bonding between the NHC ligand and the electron deficient d² metal atom. The chloro ligand in [ReNCl(HL^Ph)(L^Ph)] is labile and can be replaced by ligands such as pseudohalides or monoanionic thiolates such as diphenyldithiophosphinate (Ph₂PS₂^?) or pyridine‐2‐thiolate (pyS^?). X‐ray structure analyses of [ReN(CN)(HL^Ph)(L^Ph)] and [ReN(pyS)(HL^Ph)(L^Ph)] show that the bonding situation of the NHC ligands (Re–C(carbene) distances between 2.086(3) and 2.130(3) Å) in the product is not significantly influenced by the ligand exchange. The potentially bidentate pyS^? ligand is solely coordinated via its thiolato functionality. Hydrogen atoms of each one of the phenyl rings come close to the unoccupied sixth coordination positions of the rhenium atoms in the solid state structures of all complexes. Re–H distances between 2.620 and 2.712Å do not allow to discuss bonding, but with respect to the strong trans labilising influence of “N^3?”, weak interactions are indicated.     

Synthesis,Characterization, and Luminescent Properties of Silver(I) Complexes based on Diphosphine Ligands and 6,7‐Dicyanodipyridoquinoxaline

Five mono‐nuclear silver (I) complexes with 6,7‐dicyanodipyridoquinoxaline ligand, namely {[Ag(DPEphos)(dicnq)]NO₃}₂ · CH₃OH ( 1 ), [Ag(DPEphos)(dicnq)]BF₄ · CH₃OH ( 2 ), [Ag(XANTphos)(dicnq)]CF₃SO₃ ( 3 ), {[Ag(XANTphos)(dicnq)]NO₃}₂ ( 4 ), and [Ag(XANTphos)(dicnq)]ClO₄ · CH₂Cl₂ ( 5 ) {DPEphos = bis[2‐(diphenylphosphanyl)phenyl]ether, dicnq = 6,7‐dicyanodipyridoquinoxaline, XANTphos = 9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)xanthene} were characterized by X‐ray diffraction, IR, ¹H NMR, ³¹P NMR, fluorescence spectra, and terahertz time‐domain spectra (THz‐TDS). In the five complexes the Ag^I, which is coordinated by two kinds of chelating ligands, adopts four‐coordinate modes to generate mono‐nuclear structures. The C–H ··· π interactions lead to formation of a 1D infinite chain for complexes 2 and 3 . The crystal packing of complexes 1 and 5 reveal that they form 3D supermolecular network by several pairs of C–H ··· π interactions. The emissions of these complexes are attributed to ligands‐centered [π–π*] transition based on both of the P‐donor and N‐donor ligands.     

Synthesis,Structural Characterization,and Theoretical Studies of Silver(I) Complexes of Dihydrobis(2‐mercapto‐benzothiazolyl) Borate

The complexes [Ag{κ³‐S,S′,H‐H₂B(mbz)₂}(PR₃)]_x, ( 1 : x = 2, R = Ph; 2 : x = 1, R = Cy) (mbz = 2‐mercaptobenzothiazolyl) and amidine based dihydro(2‐mercaptobenzo‐thiazolyl) borates, [HN=C(Ph)–NH(R)–H₂B(mbz)] ( 3 : R = 2,6‐diisopropylphenyl and 4 : R = Ph) were synthesized and characterized by various spectroscopic methods and single‐crystal X‐ray crystallography. Complex [Ag{κ³‐S,S′,H‐H₂B(mbz)₂}(PPh₃)]₂ ( 1 ) has a dimeric structure in its crystalline state, in which central silver(I) atoms adopt a distorted trigonal bipyramid arrangement. In contrast, complex [Ag{κ³‐S,S′,H‐H₂B(mbz)₂}(PCy₃)] ( 2 ) has a monomeric structure in its crystalline state, in which the central silver(I) atoms adopt a distorted trigonal planar arrangement. Infrared spectroscopy was utilized as a tool for investigating the presence of M ··· H–B interactions. In addition, density functional theory (DFT) calculations were used to analyse the B–H ··· [M] bonding interaction in the metal borate complexes.     

Calix[4]arene‐Phosphine Dimers: Precursors of Flexible Metallo‐Capsules and Self‐Compacting Molecules

The first diphosphines based on a double calixarene, namely 1,4 (or 1,3)‐bis‐(5‐diphenylphosphino‐25,26,27,28‐tetrapropoxycalix[4]aren‐17‐yl)benzene ( L² , L³ ) were each prepared in four steps starting from 5,17‐dibromo‐25,26,27,28‐tetrapropoxycalix[4]arene. Upon reaction of L² with [Au(tht)(thf)]BF₄, (tht=C₄H₈S) a rigid metallo‐capsule was quantitatively formed, which adopts an oblique form owing to the distinct nature of the spacers linking the two calixarene half‐spheres. In the solid state, the 1,4‐substituted phenylene linker is turned towards the gold ion, suggesting the existence of weak bonding interactions between two aromatic CH protons of this ring and the metal centre (Au???H=2.67 Å). In contrast to this gold complex, the related silver complex shows dynamic behaviour in solution, the exchange between two enantiomeric oblique forms being facilitated by the greater stereochemical flexibility of Ag^I vs. Au^I. A heteronuclear ¹⁰⁹Ag{¹H} HMQC experiment established strong correlations between the CH protons of the phenylene linker and the ¹⁰⁹Ag ion. Dynamic behaviour similar to that observed for the silver complex was further observed in trans‐[PtCl₂? L² ], a chelate complex that could be obtained quantitatively from L² and [PtCl₂(PhCN)₂]. The intended formation of a chelate complex leading to a capsule with an endo‐oriented metal centre was achieved by reacting L³ with [Pd(allyl)(thf)₂]BF₄. The complex thus formed constitutes the first organometallic transition metal complex embedded in a cavity with large portals. Binding of [RuCl₂(p‐cymene)] to L² and L³ resulted in self‐compacting bimetallic complexes in which each calixarene basket entraps a Ru(p‐cymene) unit, thereby forming molecules occupying a minimal volume.