Heteropolymetallic Architectures as Snapshots of Transmetallation Processes at Different Degrees of Transfer

Novel heteropolymetallic architectures have been built by integrating Pd, Au and Ag systems. The dinuclear [(CNC)(PPh₃)Pd-^G11M(PPh₃)](ClO₄) (^G11M=Au ( 3 ), Ag ( 4 ); CNC=2,6-diphenylpyridinate) and trinuclear [{(CNC)(PPh₃)Pd}₂^G11M](ClO₄) (^G11M=Au ( 6 ), Ag ( 5 )) complexes have been accessed or isolated. Structural and DFT characterization unveil striking interactions of one of the aryl groups of the CNC ligand(s) with the ^G11M center, suggesting these complexes constitute models of transmetallation processes. Further analyses allow to qualitatively order the degree of transfer, proving that Au promotes the highest one and also that Pd systems favor higher degrees than Pt. Consistently, Energy Decomposition Analysis calculations show that the interaction energies follow the order Pd−Au > Pt−Au > Pd−Ag > Pt−Ag. All these results offer potentially useful ideas for the design of bimetallic catalytic systems.     

Sorption-luminescence determination of gold,silver, and platinum with the use of silica gel chemically modified with <Emphasis Type="Italic">N</Emphasis>-(1,3,4-thiodiazole-2-thiol)-<Emphasis Type="Italic">N</Emphasis>′-propylurea groups

Silica gel chemically modified with N-(1,3,4-thiodiazole-2-thiol)-N′-propylurea extracted gold(III) from solutions in the range of 6 M HCl-pH 8 and silver(I) from nitric acid solutions in the range of 6 M HNO₃-pH 8 and 1–2 M HCl at 20°C with 99.0–99.9% recovery and a sorption equilibration time of 5 min. Platinum(II) was quantitatively extracted at room temperature from solutions in the range of 4 M HCl-pH 8; the sorption equilibration time was 20 min. For the quantitative extraction of platinum(IV), it should be reduced to platinum(II). The intense yellowish orange luminescence (λ_max (Au) = 575 nm, λ_max (Ag) = 550 nm, and λ_max(Pt) = 620 nm) of surface complexes at 77 K under UV irradiation was used in the development of procedures for the low-temperature sorption-luminescence determination of gold, silver, and platinum. The detection limits were 0.15 (Au), 0.1 (Ag), and 0.05 μg (Pt) per 0.1 g sorbent. The calibration function was linear to 50 (Au, Ag) or 80 μg (Pt) per 0.1 g sorbent. The relative standard deviation in the determination of more than 5 μg of a metal was no higher than 6%. The sorption-luminescence determination procedures were tested in the determination of gold in gold-containing concentrates and their processing products and platinum in alumina-platinum catalysts.     

Extraction into methyl isobutyl ketone of metal complexes with ammonium pyrrolidine dithiocarbamate formed in strongly acidic media

It is shown that stable metal complexes with ammonium pyrrolidine dithiocarbamate (APDC) are formed in strongly acidic (0.5–6 M) solutions and can be extracted into methyl isobutyl ketone (MIBK), although APDC is normally used for extractions from solutions at pH 2–12. Percentage extraction curves are presented for 24 elements (Ag, As, Au, Bi, Cd, Co, Cu, Fe, Ga, Ge, Hg, In, It, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Sn, Tl and Zn) from solutions of hydrochloric or nitric acid with and without addition of APDC. Some elements (e.g., Fe, Ga, Ge, In and Au) show identical extractions as their chloro complexes in hydrochloric acid with or without APDC. Others (e.g., Ni, Cu, Pd, As, Ag, Sb, It, Hg and Bi) are strongly extracted (K_d ? 20), from 2 M hydrochloric or nitric acid in the presence of APDC. Palladium (K_d = 8000), Sb (K_d = 10 000), and Bi (K_d = 3500) are particularly easily extracted. The potential of the extraction system was tested by extraction and quantification of palladium from the CANMET standard ore PTC-1; the mean value found was 12.55 μg g^?1 (ppm) palladium with a relative standard deviation of 7.6% (n = 12) and a relative error of 1.2% from the recommended value of 12.70 μg g^?1.     

M@B<Subscript>9</Subscript> and M@B<Subscript>10</Subscript> molecular wheels containing planar nona- and deca-coordinate heavy group 11, 12, and 13 metals (M=Ag,Au, Cd,Hg, In,Tl)

A density functional and ab initio theory investigation on M@B₉ and M@B₁₀ molecular wheels containing planar nona- and deca-coordinate heavy group 11, 12 and 13 metals (M=Ag, Au, Cd, Hg, In, Ti) has been performed. These unusual clusters all prove to be true minima on the potential energy surfaces of the systems and σ+π double aromatic in nature. The first two vertical one-electron detachment energies of M@B₁₀⁻ (M=Ag, Au) anions and first two ionization potentials of M@B₉ (M=Ag, Au) and M@B₁₀ (M=Cd, Hg) neutrals were calculated to aid future experiments. The cluster complexes designed in this work may expend the domain of planar hyper-coordinate elements to include heavy group 11, 12, and 13 metals and serve as interesting candidates to be targeted in experiments. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. Supported by the National Natural Science Foundation of China (Grant No. 20873117)     

The treatment of Ag,Pd, Au and Pt electrodes with OH<Superscript>•</Superscript> radicals reveals information on the nature of the electrocatalytic centers

The treatment of Ag, Pd, Au and Pt electrodes with OH^• radicals can be used to get information on the nature of the electrocatalytic sites. Atomic force microscopy (AFM) measurements, various electrochemical techniques, and chemical solution analysis show a more or less effective surface dissolution of these metals upon OH^• treatment. The effect of the surface alterations on the electrocatalytic activity with respect to the quinone/hydroquinone system revealed distinct differences between Ag and Au (previous studies) on one side, and Pt and Pd on the other side. Whereas, in case of Pt and Pd, the electrocatalytic properties are obviously related to the regular surface atoms, in case of Ag and Au the active centers are highly reactive surface atoms which can be removed by OH^• radicals.     

Radiochemical neutron activation analysis for determination of Au,Ag, Pt and Pd in geological samples

A procedure for separation of Au, Ag, Pt, and Pd in geological samples has been developed. After irradiation, samples were fused with Na₂O₂ and silver was separated by filtering through a PbCl₂ filter in 4M nitric acid solution. Au, Pt and Pd were concentrated with rhodium and thiourea as rhodium sulfide and the separation process of these elements was carried out by a chromatographic method. Au, Pt and Pd were retained on a Dowex-1×8 anion column in 1M HCl. Pd was eluted from the column by using a mixture of 75% HCl acid-25% acetone. Au was eluted by using a mixture of 10% HCl-90% acetone. In the gold fraction, Pt was also determined through the photopeak of¹⁹⁹Au radionuclide (158 keV). The method was simple and rapid.     

Synthesis and Crystal Structures of Group 10 Metal Bis(dithiolate) Complexes Constructed by 2,3-Naphtho-15-Crown-5 or 2,3-Naphtho-18-Crown-6

Five novel 2,3-naphtho crown ether group 10 metal bis(dithiolate) complexes, [Na(N15C5)₂]₂[Pd(mnt)₂] (1), [Na(N15C5)]₂[Pd(i-mnt)₂] (2) and [K(N18C6)]₂[M(i-mnt)₂] (3 5) (where mnt = 1,2-dicyanoethylene-1,2-dithiolate, i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and M = Ni, Pd, Pt for complexes 3–5, respectively), have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible spectra and single crystal X-ray diffraction. X-ray diffraction analyses reveal that complexes 1 and 2 have different structural features while complexes 3–5 are structurally isomorphous. Complex 1 consists of two [Na(N15C5)₂]⁺ sandwich complex cations and one [Pd(mnt)₂]²⁻ anion, affording a zero-dimensional structure. For 2, the [Na(N15C5)]⁺ mono-capped complex cations act as the bridges linking the [Pd(i-mnt)₂]²⁻ anions into a 1D infinite chain through Na–N interactions and SȮFC and SȮFπ interactions are observed in the resulting chain. Complexes 3–5 all consist of two [K(N18C6)]⁺ complex cations and one [M(i-mnt)₂]²⁻ (M = Ni, Pd or Pt) anion and the complex molecules are linked into␣1D␣chains by the bridging K–O(ether) interactions between the adjacent [K(N18C6)]⁺ units. What’s novel is that the resulting chains are assembled into novel 2D networks through interchain π–π stacking interactions between the neighboring naphthylene moieties of N18C6. The stack model of naphthylene group in complexes 3–5 is discussed.     

Mononuclear and heterobimetallic palladium(II) and platinum(II) complexes containing the mixed ligands <Emphasis Type="Italic">N</Emphasis>-(2-pyridyl or 2-pyrimidyl) acetamide and tertiary diphosphine

Palladium(II) and platinum(II) complexes containing mixed ligands N-(2-pyridyl)acetamide (AH) or N-(2-pyrimidyl)acetamide (BH) and the diphosphines Ph₂P(CH₂) _n PPh₂, (n = 1, 2 or 3) have been prepared. The prepared complexes [Pd(A)₂(diphos)] or [Pd(B)₂(diphos)] have been used effectively to prepare bimetallic complexes of the type [(diphos)Pd(μ-L)₂M′Cl₂] where M′ = Co, Cu, Mn, Ni, Pd, Pt or SnCl₂; L = A or B. The prepared complexes were characterized by elemental analysis magnetic susceptibility, i.r. and UV–Vis spectral data. ³¹P–{¹H}-n.m.r. data have been applied to characterize the produced linkage isomers.     

Reactions of chiral phosphoramidites with complexes Pd(COD)Cl2 and Pt(COD)Cl2

Reactions of phosphoramidites based on (−)-ephedrine and [(1S)-endo]-(−)-borneol with the complexes M(COD)Cl₂ (M is Pd or Pt, and COD is cycloocta-1,5-diene) were studied. The formation ofcis andtrans complexes of the general formulas MCl₂L₂ and M₂Cl₂(μ-Cl)₂L₂ was observed. The structures of the resulting compounds were established by³¹P,¹³C, and¹⁹⁵Pt NMR and IR spectroscopy and by plasma desorption mass spectrometry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1627–1630, August, 1998.     

Some features found in the extraction of platinum group metals and gold with calix[4]arenamines and calix[n]arene thioethers from hydrochloric acid solutions

Extraction of platinum group metals and gold from hydrochloric acid solutions with calix[4]arenamines (CAA) and calix[n]arene thioethers (n = 4, 6; CTE) was studied. The high macrocyclic effects (10²–10³) are due to chelation between metals and the donor centers of macrocycles in the systems CAA-Pd and CTE-Ag, Pt^II, and Pt^IV. New CAA-based extracting systems for collective extraction of Pd, Pt, Au, Ir, and Rh and new CTE-based systems for separation of Au and Pd from Ag and Pt were justified.     

NMR studies of transformations of aminoacid complexes of Pt(II) and Pd(II) in solution. 2. Bisalaninates

Synthetic procedures are suggested for diastereomers of Pt(II) and Pd(II) bischelates with alanine: cis- and trans-Pt(l-Ala)₂ , trans-Pt(l-Ala)fd-Ala), trans-Pd(l-Ala)₂ , and trans-Pd(l-Ala)(d-AIa). Methods of their isolation in individual solid state are proposed.¹H,¹³C, and¹⁹⁵Pt NMR spectral investigations are reported for the individual diastereomers and for M(Ala)₂ racemates in DMSO solution. The trans-isomers of Pd(II) bisalaninates in DMSO solution are transformed into an equilibrium mixture of cis- and trans-isomers. For Pt(II) complexes, the cis ↔ trans equilibrium was also found but the equilibration rate is much lower than that for Pd(II) bischelates for both cis- and trans-isomer. An equilibrium 2M(l-Ala)(d-Ala) ⇌ M(l-Ala)₂+M(d-Ala)₂ is also shown to exist. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 2, pp. 312–323, March–April, 2000.     

A Theoretical Investigation into the Luminescent Properties of d8‐Transition‐Metal Complexes with Tetradentate Schiff Base Ligands

A theoretical investigation on the luminescence efficiency of a series of d⁸ transition‐metal Schiff base complexes was undertaken. The aim was to understand the different photophysics of [M‐salen]ⁿ complexes (salen=N,N′‐bis(salicylidene)ethylenediamine; M=Pt, Pd (n=0); Au (n=+1)) in acetonitrile solutions at room temperature: [Pt‐salen] is phosphorescent and [Au‐salen]⁺ is fluorescent, but [Pd‐salen] is nonemissive. Based on the calculation results, it was proposed that incorporation of electron‐withdrawing groups at the 4‐position of the Schiff base ligand should widen the ³MLCT–³MC gap (MLCT=metal‐to‐ligand charge transfer and MC=metal centered, that is, the dd excited state); thus permitting phosphorescence of the corresponding Pd^II Schiff base complex. Although it is experimentally proven that [Pd‐salph‐4E] (salph=N,N′‐bis(salicylidene)‐1,2‐phenylenediamine; 4E means an electron‐withdrawing substituent at the 4‐position of the salicylidene) displays triplet emission, its quantum yield is low at room temperature. The corresponding Pt^II Schiff base complex, [Pt‐salph‐4E], is also much less emissive than the unsubstituted analogue, [Pt‐salph]. Thus, a detailed theoretical analysis of how the substituent and central metal affected the photophysics of [M‐salph‐X] (X is a substituent on the salph ligand, M=Pt or Pd) was performed. Temperature effects were also investigated. The simple energy gap law underestimated the nonradiative decay rates and was insufficient to account for the temperature dependence of the nonradiative decay rates of the complexes studied herein. On the other hand, the present analysis demonstrates that inclusions of low‐frequency modes and the associated frequency shifts are decisive in providing better quantitative estimates of the nonradiative decay rates and the experimentally observed temperature effects. Moreover, spin–orbit coupling, which is often considered only in the context of radiative decay rate, has a significant role in determining the nonradiative rate as well.     

Synthesis, structure, and thermal transformations of double complex salts [Au(C4H13N3)Cl][MCl6]· nH2O (M = Ir, Pt; n = 0–2)

Double complex salts [Au(C₄H₁₃N₃)Cl][MCl₆]·nH₂O (M = Ir, Pt; n = 0–2) were synthesized. According to X-ray diffraction data, compounds with n = 1.5 are isostructural; the crystal structure is composed of the complex cations [Au(dien)Cl]²⁺ (dien is diethylenetriamine), the complex anions [MCl₆]²⁻, and water molecules of crystallization. Thermolysis of the double complex salts under hydrogen and helium was studied. The formation of nonequilibrium solid solutions based on Ir in the Au-Ir system and based on Pt in the Au-Pt system was demonstrated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 416–421, March, 2006.     

NMR studies of transformations of Pt(II) and Pd(II) complexes with amino acids in solution. 1. Glycine complexes

¹H,¹³C, and¹⁹⁵Pt NMR studies were performed for Pt(ll) and Pd(II) complexes with glycine cis- and trans-M(Gly)₂, trans-Pd(GlyH)₂Cl₂ , cis- and trans-Pt(GlyH)₂Cl₂ , Na[Pd(GIy)Cl₂], and K[Pt(Gly)CI₂] in donor type solvents DMSO and H₂O. It is shown that a cis ↔ trans equilibrium takes place in these solvents and that the equilibration rate is low for Pt(II) complexes and high for Pd(II) complexes. Therefore, the cis- and trans-complexes of Pt(II) may be recorded by NMR spectroscopy in the individual state, whereas for Pd(II) there is an equilibrium mixture of cis- and trans-isomers. Solvolysis of Cl-containing complexes in DMSO is studied. A mechanism of solvolysis involving eis ↔ trans isomerization of the dichloro complexes of Pd(II) is suggested. NMR spectral data for some solvolysis products are given. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 2, pp. 300–311, March–April, 2000.     

Analytical characterization of a silica gel sorbent with thioetheric sites

The sorption behavior of a newly synthesized silica gel sorbent with thioetheric sites (STS) towards microgram levels of Au(III), Pt(IV) and Pd(II) was studied. Au(III) is quantitatively (>95%) sorbed in the pH region of 1–9. The sorption of Pt(IV) starts at pH 1 and does not exceed 25% in the entire pH region examined. The sorption of Pd(II) starts at pH 7 and reaches 80% at pH 9. The sorption of Au(III) on STS at pH 1 is not affected by milligram amounts of Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) or Co(II). Au(III) is quantitatively eluted with a 5% aqueous solution of thiourea. The adsorption capacity of STS towards Au(III) is 195 mg g⁻¹. The detection limit (DL) of Au(III) (3σ, n = 9) is 25 ng mL⁻¹. The RSD at a level of 10 × DL is about 2%. Solid-phase extraction of trace amounts of Au(III) on the STS sorbent, followed by its flame AAS determination in the eluate was applied to the determination of gold in geological samples. The results obtained for the gold content in the samples were in good agreement with those of the ICP-AES analysis.     

Effect of polyether diamine on gas permeation properties of organic-inorganic hybrid membranes

The quantitative incorporation and high dispersion of platinum nanoparticles into MCM-41 has been carried out by the coordination between Pt(IV) ion and APTMS-anchored MCM-41. Before and after calcination of Pt/APTMS/MCM41 samples, the Pt content in samples was evaluated from home-made photoacoustic spectrometer (PAS). The PAS bands at 350 nm and 450 nm can be assigned to d–d transition bands of Pt complexes. By increasing the concentration of Pt solution, the PAS intensity of Pt/APTMS/MCM41 was increased proportionally up to 1.0×10⁻² M, and remained constant above 1.0×10⁻² M. It can be attributed to the saturation of Pt content within Pt/APTMS/MCM41. The Pt content in the saturated Pt/APTMS/MCM41 was 8.5 wt% (the theoretical value), 9.7 wt% (measured by EDX) and 9.2 wt% (measured by ESCA), respectively. This indicates that the content of Pt precursor within MCM-41 could be controlled by the concentration of Pt precursor solution. The PAS intensity of calcined Pt/APTMS/MCM41's in H₂ flow was increased up to 1.0×10⁻² M and remained nearly constant above 1.0×10⁻² M. Therefore, we suggest that the formation of Pt complexes with APTMS-anchored MCM-41 made it possible to incorporate quantitatively Pt nanoparticles in the range of 0.5–9.2 wt% within MCM-41 channels.     

Application of a new formulation of the periodic law to predicting the proton affinity of elements

To illustrate the efficiency of a previously proposed new formulation of the Periodic Law, the proton affinities and gas-phase basicities of 20 elements in the p- and d-blocks were predicted. These properties were considered as a function of the total number of p- or d-electrons in an atom, rather than depending on the nuclear charge or the number of outer-shell electrons. The analysis was performed block by block separately. For p elements, the kainosymmetry and additional periodicity were taken into account. Equations were deduced and then used for predicting the proton affinities and gas-phase basicities of p ⁴–p ⁶ elements (Se, Te, Po, At, and Rn) and d ²–d ¹⁰ elements (Zr, Nb, Mo, Tc, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg).     

Structural and Photophysical Study on Heterobimetallic Complexes with d8–d10 Interactions Supported by Carborane Ligands: Theoretical Analysis of the Emissive Behaviour

Heterobimetallic complexes of formula [M{(PPh₂)₂C₂B₉H₁₀}(S₂C₂B₁₀H₁₀)M′(PPh₃)] (M=Pd, Pt; M′=Au, Ag, Cu) and [Ni{(PPh₂)₂C₂B₉H₁₀}(S₂C₂B₁₀H₁₀)Au(PPh₃)] were obtained from the reaction of [M{(PPh₂)₂C₂B₁₀H₁₀}(S₂C₂B₁₀H₁₀)] (M=Pd, Pt) with [M′(PPh₃)]⁺ (M′=Au, Ag, Cu) or by one‐pot synthesis from [(SH)₂C₂B₁₀H₁₀], (PPh₂)₂C₂B₁₀H₁₀, NiCl₂ ? 6 H₂O, and [Au(PPh₃)]⁺. They display d⁸–d¹⁰ intermetallic interactions and emit red light in the solid state at 77 K. Theoretical studies on [M{(PPh₂)₂C₂B₉H₁₀}(S₂C₂B₁₀H₁₀)Au(PPh₃)] (M=Pd, Pt, Ni) attribute the luminescence to ligand (thiolate, L)‐to‐“P₂‐M‐S₂” (ML′) charge‐transfer (LML′CT) transitions for M=Pt and to metal (M)‐to‐“P₂‐M‐S₂” (ML′) charge‐transfer (MML′CT) transitions for M=Ni, Pd.     

Neutron activation analysis of platinum metals in airborne particulate matter

A method is described for the determination of Au, Pt, Pd, Ag and Ir in two atmospheric aerosol samples, namely in Ghent and in the Milanese intercomparison sample. After neutron irradiation the samples are fused with Na₂O₂. Gold is extracted with ethylacetate, Pt precipitated as (NH₄)₂PtCl₆ Pd as dimethylglyoximate, Ag as chloride and Ir separated by anion-exchange adsorption and batch extraction. Ge(Li) gamma-spectrometry is applied for all determinations. The concentrations in ng·g⁻¹ in the samples are respectively: Au: 49 and 3000; Pt: below 100 for both samples; Pd: 7 and 28; Ag: 6000 and 14 000; Ir: 2.5 and 1.3.     

Selective extraction of platinum,iridium, and palladium with macrocyclic endo-receptors from hydrochloric acid solutions

Extraction of Pt, Ir, Pd by the macrocyclic polyethers dibenzo-18-crown-6 (DB18C6) and cis-syncis-dicyclohexyl-18-crown-6 (DCH18C6, isomer A) in organic solvents (chloroform, dichloroethane) from 3–10 M aqueous HCl was studied. It was found that DCH18C6 in dichloroethane excellently extracted Pt, Ir, and Pd in the presence of KSCN. Re-extraction of Pt, Ir, and Pd from the organic phase can be fulfilled by 1 M HNO₃. Thus, the macrocyclic polyethers are effective reagents for isolation of Pt, Ir, and Pd from HCl solutions.