AgCl Research Articles

IPr# Complexes-Highly-Hindered, Sterically-Bulky Cu(I) and Ag(I) N-Heterocyclic Carbenes: Synthesis, Characterization, and Reactivity.

Metal-N-heterocyclic carbene (M-NHC) complexes are well-known as an important class of organometallic compounds widely used in transition-metal catalysis. Taking into account that the steric hindrance around the metal center is one of the major effects in M-NHC catalysis, the development of new, sterically hindered M-NHC complexes is an ongoing interest in this field of research. Herein, we report the synthesis and characterization of exceedingly sterically hindered, well-defined, air- and moisture-stable Cu(I) and Ag(I) complexes, [Cu(NHC)Cl] and [Ag(NHC)Cl], in the recently discovered IPr# family of ligands that hinge upon modular peralkylation of anilines. The complexes in both the BIAN and IPr families of ligands are reported. X-ray crystallographic analyses and computational studies were conducted to determine steric effects, Frontier molecular orbitals, and bond orders. The complexes were evaluated in the model hydroboration of the alkynes. We identified [Cu(BIAN-IPr#)Cl] and [Ag(BIAN-IPr#)Cl] as highly reactive catalysts with the reactivity outperforming the classical IPr and IPr*. Considering the attractive features of well-defined Cu(I)-NHC and Ag(I)-NHC complexes, this class of sterically bulky yet wingtip-flexible complexes will be of interest for catalytic processes in various areas of organic synthesis and catalysis.

Technical note: Optimizing the in situ cosmogenic 36Cl extraction and measurement workflow for geologic applications

Abstract. In situ cosmogenic 36Cl analysis by accelerator mass spectrometry (AMS) is routinely employed to date Quaternary surfaces and assess rates of landscape evolution. However, standard laboratory preparation procedures for 36Cl dating require the addition of large amounts of isotopically enriched chlorine spike solution; these solutions are expensive and increasingly difficult to acquire from commercial sources. In addition, the typical workflow for 36Cl dating involves measuring both 35Cl/37Cl and 36Cl/Cl concurrently on the high-energy (post-accelerator) end of the AMS system, but 35Cl/37Cl determinations using this technique can be complicated by isotope fractionation and system memory during measurement. The traditional workflow also does not provide 36Cl extraction laboratories with the data needed to calculate native Cl concentrations in advance of 36Cl/Cl measurements. In light of these concerns, we present an improved workflow for extracting and measuring chlorine in geologic materials. Our initial step is to characterize 35Cl/37Cl on sample aliquots of up to ∼1 g prepared in Ag(Cl, Br) matrices, which greatly reduces the amount of isotopically enriched spike solution required to measure native Cl content in each sample. To avoid potential issues with isotope fractionation through the accelerator, 35Cl/37Cl is measured on the low-energy, pre-accelerator end of the AMS line. Then, for 36Cl/Cl measurements, we extract Cl as AgCl or Ag(Cl, Br) in analytical batches with a consistent total Cl load across all samples; this step is intended to minimize source memory effects during 36Cl/Cl measurements and allows the preparation of AMS standards that are customized to match known Cl contents in the samples. To assess the efficacy of this extraction and measurement workflow, we compare chlorine isotope ratio measurements on seven geologic samples prepared using standard procedures and the updated workflow. Measurements of 35Cl/37Cl and 36Cl/Cl are consistent between the two workflows, and 35Cl/37Cl values measured using our methods have considerably higher precision than those measured following standard protocols. The chemical preparation and measurement workflow presented here (1) reduces the amount of isotopically enriched chlorine spike used per rock sample by up to 95 %; (2) identifies rocks with high native Cl concentrations, which may be lower priority for 36Cl surface exposure dating, at an early stage of analysis; and (3) allows laboratory users to maintain control over the total chlorine content within and across analytical batches. These methods can be incorporated into existing laboratory and AMS protocols for 36Cl analyses and will increase the accessibility of 36Cl dating for geologic applications.

Advancing on ametrine pesticide detection through surface‐enhanced Raman spectroscopy and Ag colloid: Understanding the pH effect and the adsorption mechanism supported by theoretical calculation

AbstractThe excessive use of pesticides has detrimental effects on the ecosystem, leading to soil contamination and the spread of pollution beyond the targeted areas. Concerns arise regarding the permissible limits of pesticides, typically around 10−8 mol/L. In this study, we employed surface‐enhanced Raman spectroscopy (SERS), a highly sensitive and selective technique, to investigate the behavior of the pesticide ametrine (AMT) on silver colloids. The Ag nanoparticles (AgNPs) exhibited an average size of (26 ± 2) nm and a zeta potential of (−30 ± 1) mV in the absence of AMT, which decreased to (−24 ± 1) mV in the presence of AMT, resulting in mild AgNPs aggregation, with the average diameter of AgNPs increasing to approximately 300 nm. This aggregation is advantageous, as they provide active sites for pesticide detection. Besides, the purification method employed ensured that AMT remained undegraded, and various conformations of AMT were simulated using Ag clusters to study the SERS effect. Comparison with the experimental spectra indicated that the SERS‐4 conformer closely resembled the experimental spectrum, suggesting simultaneous interaction between the Ag surface and the sulfur (S) and nitrogen (N) atoms of the AMT triazine ring. Notably, changes in the AMT molecule were observed with pH variations: at pH below 5, hydroxylation occurred, resulting in an Ag–Cl stretching at 241 cm−1 in the SERS spectra. Conversely, at pH above 5 (pH 6–13), the presence of bands at 230 and 219 cm−1 in the SERS spectra indicate the formation of Ag–N and Ag–S bonds, respectively, between the AMT and the AgNPs. Furthermore, the study successfully detected AMT at pH 7, establishing a limit of detection (LOD) of 1.36 × 10−8 mol/L (3 ppb) based on the SERS spectra. These findings underscore the applicability of the SERS technique in the sensitive and selective detection of AMT, offering a promising approach for monitoring the presence of this pesticide in environmental samples.

A 12-Vertex Metallacarborane of Silver(I).

The discovery of ferrocene in 1951 was a significant landmark in the field of organometallic chemistry, and since then, numerous sandwich- or half-sandwich metallic complexes have been reported. However, silver stands as an intriguing exception in this regard, and knowledge of its bonding situation has remained undisclosed. Herein, unprecedented 12-vertex metallacarboranes of Ag(I) (2a and 2b) were synthesized through the reaction of sodium hexamethyldisilazide (NaHMDS) with the mixture of nido-C2B9 carborane anion-supported N-heterocyclic carbene precursors (1a and 1b) and [Ag(PPh3)Cl]4. The X-ray structural analysis of the resulting metallacarboranes revealed a unique "slipped" half-sandwich structure, which is a rarity among cyclopentadienyl analogues. DFT calculations provided insights into the asymmetric π-interactions between the pentagonal C2B3 face and the silver ion.

Challenges in surface‐enhanced Raman scattering signal for ethephon detection: Theoretical and experimental approaches

AbstractEthephon, a widely used growth regulator in fruits and vegetables, requires careful monitoring because of its toxicity. However, as far as we know, only two works are found in the literature regarding surface‐enhanced Raman scattering (SERS) ethephon detection. Indeed, obtaining the SERS signal revealed to be challenging. Therefore, we have evaluated the SERS signal of ethephon using theoretical (as density functional theory and charge‐assisted fragment interaction) and experimental approaches, addressing this limited literature knowledge. Theoretical Raman spectra with Ag or Au atoms at reactive sites exhibited enhanced ethephon SERS signal via AgCl bonding, consistent with the experimental data. Multiple experimental procedures were employed to obtain the SERS signal, including pH variations, salt addition, excitation laser lines, time dependency, and different SERS substrates (Ag colloid and Ag island films). Salt addition (NaCl) improved SERS signal, correlating with Ag colloid aggregation. Analysis in Ag colloid showed the pH 7.0 as optimal for ethephon detection, using freshly prepared Ag colloid + ethephon dispersion with ethephon powder being directly dissolved into Ag colloid. Only the AgCl band intensity improved with time. Ag colloid (wet medium — 633 nm laser line) outperformed Ag island films (dry medium — 785 nm laser line).

Efficient electrocatalytic reduction of CO2 to CO on highly dispersed Ag nanoparticles confined by Poly(ionic liquid)

Efficient electrocatalytic conversion of CO2 to CO is a promising mode for CO2 transformation driven by renewable electricity. Herein, varied poly(ionic liquid)-Ag (PIL-Ag) hybrids are facilely synthesized by impregnating chloride-based PIL with silver salts. The remarkable confinement effect of PIL on the patterns of in-situ formed highly dispersed Ag–Cl species leads to the corresponding complexes, clusters, and nanoparticles (NPs) in the inner domain, while their distribution is highly correlated to both microstructures of the PIL skeleton and silver salts launched. As a result, the highly dispersed imidazolium-pyridine-imidazolium tridentate sites at the PIL layer combined with a compatible supply rate of Ag+ cation enables the formation of abundant AgCl NPs in PIL-Cl@AgOAc-1.0, which provided a high CO selectivity of 96.8 % with a high partial current density of 207.0 mA cm−2 at –0.91 V (vs RHE) in 1 M KOH. Besides, long-term electrolysis was conducted at 100 mA cm−2 for 100 h with a slight decay of selectivity to ∼ 86 %. Further, despite the similar intrinsic activity of three Ag–Cl species, the patterns of Ag–Cl species, the number of active sites, and the mass transfer of reactants within the hybrids jointly determine the apparent electrocatalytic performance obtained at high rates.

Boosting the photocatalytic activation of molecular oxygen and photodegradation of tetracycline: The role of interfacial synergistic effect of cocatalyst and dopants

Utilizing reactive oxygen species (ROS), which are generated by the activation of molecular oxygen (O2) in oxidation reaction, is a promising method for pollutant degradation. However, it is limited by the commonly low efficiency of O2 activation and carrier separation. Herein, as a model system, Ag cocatalyst and Cl doping modified g-C3N4 (Ag/Cl-CN) was constructed to improve the ability of O2 activation. Results showed that Ag/Cl-CN could effectively convert more O2 into ROS than pristine g-C3N4 (CN), and individually decorated CN (Ag-CN and Cl-CN). A series of experiments and DFT calculations revealed that the deposition of Ag could promote charge separation resulting in more charges accumulated around O2 and the introduction of Cl led to a stronger adsorption capacity for O2. Therefore, due to the synergistic effect of Ag cocatalyst and Cl dopant, Ag/Cl-CN generated higher concentrations of O2− and displayed much better activity for photocatalytic degradation of tetracycline (TC) than CN, Ag-CN and Cl-CN.

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

P–Nitrobenzyl-substituted N–heterocyclic carbene in Silver(I) and Gold(I) complexes and their antibacterial activities

The synthesis of the silver(I) N–heterocyclic carbene [Ag(NBMIM)Cl]2 (2) from the reaction of imidazolium salt {NBMIM}Cl (1a) (NBMIM = 1–methyl–3–(4–nitrobenzyl)–1H–imidazol–3–ium) and silver(I) oxide was achieved. Compound {NBMIM}PF6 (1b) was also obtained by a counteranion exchange reaction. Compound 2 was used as a transmetalation agent to form Au(I) monocarbene complex (3a) and biscarbene complex (3b), by using [AuCl(SMe2)]. All compounds were characterized in solution by infrared spectroscopy and by 1H and 13C{1H} NMR. The molecular structures of compounds {NBMIM}PF6 (1b), [Ag(NBMIM)Cl]2 (2), and [Au(NBMIM)Cl] (3a) were also determined by single crystal X–ray diffraction studies. The molecular structure of silver complex 2 showed a 1D–staircase structure with Ag⋯Ag and Ag⋯Cl intermolecular interactions. Compounds 2 and 3a were also characterized by elemental analysis, powder X–ray diffraction (PXRD), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) measurement. In preliminary in vitro antibacterial assays, compounds 2 and 3a were tested against four bacterial strains: two Gram positive (S. aureus and B. subtilis) and two Gram negative species (P. aeruginosa and E. coli) by Kirby–Bauer’s disk diffusion method. Compound 2 exhibited moderate antibacterial activity against both types of bacteria. Both silver(I) and gold(I) N–heterocyclic carbenes showed from good to high antibacterial activity against S. aureus and P. aeruginosa and moderate activity against B. subtilis and E. coli strains.

Accelerated formation of persistent holographic gratings based on one-directional electron transfer in KCl-Ag/Ta2O5 nanocomposites

Permanent preservation of data is essential for massive information recording. Combination of semiconductor with plasmonic nanoparticles has been applied in multicolor display and high-density optical storage. However, bidirectional electron transfer occurs at the Schottky interface under UVA irradiation, resulting in reversible photochemical reaction, information erasure, low recording efficiency and writing rate. To address these issues, a novel Schottky heterostructure of Ag/Ta2O5 modified with alkali halide is developed to realize photoinduced one-directional electron transfer from metal to semiconductor. The recorded information in such a medium of KCl-Ag/Ta2O5 presents excellent holographic storage stability even under exposure of a strong UVA ray (360 nm, 385 mW/cm2). Meanwhile, grating growth rate and efficiency are significantly enhanced by optimizing Ag particle distance and Cl− anion loading amount. This work provides an important strategy for fast and persistent data storage.

Recovery of Ag, Au, and Pt from Printed Circuit Boards by Pressure Leaching

Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H2O, Au–Cl–H2O and Pt–Cl–H2O were constructed to know the possible species in the solution.

Facile N9-Alkylation of Xanthine Derivatives and Their Use as Precursors for N-Heterocyclic Carbene Complexes.

The xanthine-derivatives 1,3,7-trimethylxanthine, 1,3-dimethyl-7-benzylxanthine and 1,3-dimethyl-7-(4-chlorobenzyl)xanthine are readily ethylated at N9 using the cheap alkylating agents ethyl tosylate or diethyl sulfate. The resulting xanthinium tosylate or ethyl sulfate salts can be converted into the corresponding PF6− and chloride salts. The reaction of these xanthinium salts with silver(I) oxide results in the formation of different silver(I) carbene-complexes. In the presence of ammonia, ammine complexes [Ag(NHC)(NH3)]PF6 are formed, whilst with Et2NH, the bis(carbene) salts [Ag(NHC)2]PF6 were isolated. Using the xanthinium chloride salts neutral silver(I) carbenes [Ag(NHC)Cl] were prepared. These silver complexes were used in a variety of transmetallation reactions to give the corresponding gold(I), ruthenium(II) as well as rhodium(I) and rhodium(III) complexes. The compounds were characterized by various spectroscopic methods as well as X-ray diffraction.

Silver N‐heterocyclic carbene complexes bearing fluorinated benzyl group: Synthesis, characterization, crystal structure, computational studies, and inhibitory properties against some metabolic enzymes

A series of the silver N‐heterocyclic carbene (NHC) complexes have been synthesized from the reactions between benzimidazolium salts bearing fluorinated benzyl group and Ag2O via the deprotonation method. All Ag(I)NHC complexes were characterized by known spectroscopic techniques (1H nuclear magnetic resonance [NMR], 13C NMR, and Fourier transform infrared [FT‐IR]) and elemental analysis. The molecular structures of the two complexes were unambiguously elucidated through single‐crystal X‐ray diffraction analysis. Namely, X‐ray studies show that the coordination geometry around the Ag(I) atom in the case of complex 2c is revealed to be almost linear with C–Ag–Cl angle, whereas in complex 2e, it appears as a nonlinear structure. The inhibitory profiles of these new complexes are investigated on some metabolic enzymes. Representatively, the most potent complex against human carbonic anhydrase isoenzymes I and II (hCAs I and II), 2d, was 1.8 times more potent than standard inhibitor acetazolamide against hCAs I and II. On the other hand, complexes 2c and 2b as most potent compounds against both cholinesterase enzymes was around 5 and 1.6 times more potent than tacrine against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively. The most active α‐glucosidase inhibitor 2d had similar activity to acarbose as a standard inhibitor. Furthermore, it confirms its in vitro studies as a result of molecular docking studies for each enzyme with (i) binding energy and inhibition constant values and (ii) the definition of the best conformation and nonbonding interactions of the related complexes (2b, 2c, and 2d) against the different target proteins.

High-throughput screening to modulate electronic and optical properties of alloyed Cs2AgBiCl6 for enhanced solar cell efficiency

The lead-free double perovskite material (viz. Cs2AgBiCl6) has emerged as an efficient and environmentally friendly alternative to lead halide perovskites. To make Cs2AgBiCl6 optically active in the visible region of solar spectrum, band gap engineering approach has been undertaken. Using Cs2AgBiCl6 as a host, band gap and optical properties of Cs2AgBiCl6 have been modulated by alloying with M(I), M(II), and M(III) cations at Ag-/Bi-sites. Here, we have employed density functional theory (DFT) with suitable exchange-correlation functionals in light of spin–orbit coupling (SOC) to determine the stability, band gap and optical properties of different compositions, that are obtained on Ag–Cl and Bi–Cl sublattices mixing. On analyzing 64 combinations within Cs2AgBiCl6, we have identified 19 promising configurations having band gap sensitive to solar cell applications. The most suitable configurations with Ge(II) and Sn(II) substitutions have spectroscopic limited maximum efficiency (SLME) of 32.08% and 30.91%, respectively, which are apt for solar cell absorber.

Comparative Study of the Ethanolic and Aqueous Avicennia marina Mangrove Extracts on the Biosynthesis of AgCl@TiO2 Nanocomposite

The biosynthesis of nanomaterials is an important aspect of nanotechnology due to its cost-effective and eco-friendly procedure. The present study was carried out to fabricate AgCl@TiO2 nanocomposite using the aqueous and ethanolic leaf extracts of Avicennia marina mangrove plant as a reducing and stabilizing agent (RSA). The effect of aqueous and ethanolic leaf extracts with different concentrations on biosynthesis of AgCl@TiO2 nanoparticles (NPs) was systematically studied by X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), UV-visible diffuse reflectance spectroscopy (UV-visible DRS) and fourier transform infrared spectrometer (FT-IR). The results illustrated the successful synthesis of AgCl@TiO2 nanocomposite without any impurity phase using aqueous extract. AgCl NPs were uniformly distributed on the surface of TiO2. The absorption intensity of AgCl@TiO2 with a bandgap energy of 2.95 was improved both in the UV and VL region and displayed stronger absorption compared with pure TiO2. FTIR analysis confirmed that the biosynthesized AgCl@TiO2 by using aqueous leaf extract was not just an easy physical mixture of Ag and TiO2 species but it was a molecular-level combining of Ti–O and Ag–O domains in the nanocomposite.

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

The NHC supersilyl silver complex [Ag(IPr)SitBu3] (IPr = NHCIPr) 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.

An Efficient A3 Coupling Catalyst Based on a Silver Complex Bearing N‐Heterocyclic Carbene and Homoscorpionate Bis(3‐methyl‐mercaptoimidazolyl)borate Ligands

AbstractReaction of Ag(IPr)(Cl), 1 [IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene] with sodium precursors Na(mim) [mim=dihydrobis(methimazolyl)borate] and Na(Bb) [Bb=dihydrobis(2‐mercapto‐benzothiazolyl)borate] formed two novel silver complexes [Ag(IPr)(mim)], 2 and [Ag(IPr)(Bb)], 3. These complexes catalyzed three‐component coupling reaction of a series of aldehydes with alkynes and amines. The efficiency of these novel catalysts compared with that of 1 and Au(IPr)(Cl), 4.

Quest for Compounds at the Verge of Charge Transfer Instabilities: The Case of Silver(II) Chloride †

Electron-transfer processes constitute one important limiting factor governing stability of solids. One classical case is that of CuI2, which has never been prepared at ambient pressure conditions due to feasibility of charge transfer between metal and nonmetal (CuI2 → CuI + ½ I2). Sometimes, redox instabilities involve two metal centers, e.g., AgO is not an oxide of divalent silver but rather silver(I) dioxoargentate(III), Ag(I)[Ag(III)O2]. Here, we look at the particularly interesting case of a hypothetical AgCl2 where both types of redox instabilities operate simultaneously. Since standard redox potential of the Ag(II)/Ag(I) redox pair reaches some 2 V versus Normal Hydrogen Electrode (NHE), it might be expected that Ag(II) would oxidize Cl− anion with great ease (standard redox potential of the ½ Cl2/Cl− pair is + 1.36 V versus Normal Hydrogen Electrode). However, ionic Ag(II)Cl2 benefits from long-distance electrostatic stabilization to a much larger degree than Ag(I)Cl + ½ Cl2, which affects relative stability. Moreover, Ag(II) may disproportionate in its chloride, just like it does in an oxide; this is what AuCl2 does, its formula corresponding in fact to Au(I)[Au(III)Cl4]. Formation of polychloride substructure, as for organic derivatives of Cl3− anion, is yet another possibility. All that creates a very complicated potential energy surface with a few chemically distinct minima i.e., diverse polymorphic forms present. Here, results of our theoretical study for AgCl2 will be presented including outcome of evolutionary algorithm structure prediction method, and the chemical identity of the most stable form will be uncovered together with its presumed magnetic properties. Contrary to previous rough estimates suggesting substantial instability of AgCl2, we find that AgCl2 is only slightly metastable (by 52 meV per formula unit) with respect to the known AgCl and ½ Cl2, stable with respect to elements, and simultaneously dynamically (i.e., phonon) stable. Thus, our results point out to conceivable existence of AgCl2 which should be targeted via non-equilibrium approaches.

Synthesis of Trimetallic (HPd@M2Au8)3+ Superatoms (M = Ag, Cu) via Hydride-Mediated Regioselective Doping to (Pd@Au8)2.

We have recently reported that hydride (H–) doped superatom (HPd@Au8)+ protected by eight PPh3 ligands selectively grew into (HPd@Au10)3+ by the nucleophilic addition of two Au(I)Cl units. In the present study, (HPd@Au8)+ was successfully converted to unprecedented trimetallic (HPd@M2Au8)3+ superatoms (M = Ag, Cu) by controlled doping of two Ag(I)Cl or Cu(I)Cl units, respectively. Single-crystal X-ray diffraction analysis demonstrated that two Ag(I) or Cu(I) ions were regioselectively incorporated. Theoretical calculations suggested that hydrogens in (HPd@M2Au8)3+ (M = Au, Ag, Cu) occupy the same bridging site between the central Pd atom and the surface Au atom. (HPd@Ag2Au8)3+ exhibited photoluminescence at 775 nm, with the enhanced quantum yield of 0.09%, although it is structurally and electronically equivalent with (HPd@Au10)3+. This study demonstrates that hydride-mediated growth process is a promising atomically-precise bottom-up synthetic method of new multimetallic superatoms.

Copper and Silver Complexes of a Redox-Active Diphosphine-Diboraanthracene Ligand.

Redox-active ligands and Z-type acceptor ligands have emerged as promising strategies for promoting multielectron redox chemistry at transition-metal centers. Herein, we report the synthesis and characterization of copper and silver complexes of a diphosphine ligand featuring a diboraanthracene core (B2P2, 9,10-bis(2-(diisopropylphosphino)phenyl)-9,10-dihydroboranthrene) that is capable of serving as both a redox reservoir and a Z-type ligand. Metalation of B2P2 with CuX (X = Cl, Br, I) results in the formation of bimetallic complexes of the formula (B2P2)Cu2X2 of two different structure types, depending on the halide. The Cu(I) cation [Cu(B2P2)]+ can be accessed by direct metalation of B2P2 with [Cu(CH3CN)4][PF6] or by halide abstraction with Na[BArF4] (ArF = 3,5-bis(trifluoromethyl)phenyl) with concomitant expulsion of CuX from the bimetallic Cu2X2 complexes. Metalation of B2P2 with AgCl results in the formation of the zwitterion Ag(B2P2)Cl featuring a diphosphine Ag cation tethered to a chloroborate anion. Metathesis of chloride for the noncoordinating [BArF4]- affords the cation [Ag(B2P2)]+. The cations [Cu(B2P2)]+ and [Ag(B2P2)]+ exhibit quasireversible reduction events at ∼ -1.6 V versus the ferrocene/ferrocenium redox couple, and the thermally sensitive radicals that result from their reduction, Cu(B2P2) and Ag(B2P2), were characterized by EPR spectroscopy and, in the case of the latter, single-crystal X-ray diffraction. Electronic structure calculations suggest these neutral radicals are best described as zwitterions with reduction centered at the diboraanthracene core.