Organosilver Compounds Research Articles

Cross-Coupling Reactions Enabled by Well-Defined Ag(III) Compounds: Main Focus on Aromatic Fluorination and Trifluoromethylation.

AgIII compounds are considered strong oxidizers of difficult handling. Accordingly, the involvement of Ag catalysts in cross-coupling via 2e- redox sequences is frequently discarded. Nevertheless, organosilver(III) compounds have been authenticated using tetradentate macrocycles or perfluorinated groups as supporting ligands, and since 2014, first examples of cross-coupling enabled by AgI /AgIII redox cycles saw light. This review collects the most relevant contributions to this field, with main focus on aromatic fluorination/perfluoroalkylation and the identification of AgIII key intermediates. Pertinent comparison between the activity of AgIII RF compounds in aryl-F and aryl-CF3 couplings vs. the one shown by its CuIII RF and AuIII RF congeners is herein disclosed, thus providing a more profound picture on the scope of these transformations and the pathways commonly associated to C-RF bond formations enabled by coinage metals.

Electrophilicity of neutral square-planar organosilver(III) compounds.

Neutral Ag(III) complexes stabilised with just monodentate ligands are here unambiguously established. In a series of square-planar (CF3)3Ag(L) compounds with hard and soft Group 15 donor ligands, L, the metal center has been found to exhibit substantial acidity favouring apical coordination of an additional ligand under no coordination constraints.

A Five-Coordinate Compound with Inverted Ligand Field: An Unprecedented Geometry for Silver(III).

By using suitable synthetic procedures, we have first isolated the square‐planar organosilver(III) compounds [PPh4][trans‐(CF3)2AgX2] [X=Cl (1 a), Br (2 a)]. The geometry and stereochemistry of the chloro‐derivative 1 a have been unambiguously established by single‐crystal X‐ray diffraction (SC‐XRD) methods. Following our calculations on the relative stability of the cis‐/trans‐[(CF3)2AgX2]− couples (X=F, Cl, Br, I), the experimentally obtained compounds 1 a and 2 a appear to be kinetically favored stereoisomers. They display some tendency to associate an additional X− ligand affording rare five‐coordinate AgIII species [(CF3)2AgX3]2−. Interestingly, compound [PPh4]2[(CF3)2AgBr3] (3) has been identified by SC‐XRD methods as the first AgIII derivative with trigonal symmetry in general and trigonal bipyramidal geometry in particular. This unusual five‐coordinate species also exhibits inverted ligand field.

A Five‐Coordinate Compound with Inverted Ligand Field: An Unprecedented Geometry for Silver(III)

AbstractBy using suitable synthetic procedures, we have first isolated the square‐planar organosilver(III) compounds [PPh4][trans‐(CF3)2AgX2] [X=Cl (1 a), Br (2 a)]. The geometry and stereochemistry of the chloro‐derivative 1 a have been unambiguously established by single‐crystal X‐ray diffraction (SC‐XRD) methods. Following our calculations on the relative stability of the cis‐/trans‐[(CF3)2AgX2]− couples (X=F, Cl, Br, I), the experimentally obtained compounds 1 a and 2 a appear to be kinetically favored stereoisomers. They display some tendency to associate an additional X− ligand affording rare five‐coordinate AgIII species [(CF3)2AgX3]2−. Interestingly, compound [PPh4]2[(CF3)2AgBr3] (3) has been identified by SC‐XRD methods as the first AgIII derivative with trigonal symmetry in general and trigonal bipyramidal geometry in particular. This unusual five‐coordinate species also exhibits inverted ligand field.

Cross-Coupling through Ag(I)/Ag(III) Redox Manifold.

In ample variety of transformations, the presence of silver as an additive or co-catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross-coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2e- redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through AgI /AgIII redox catalysis (i. e. CEL coupling), namely: i) easy AgI /AgIII 2e- oxidation mediated by air; ii) bpy/phen ligation to AgIII ; iii) boron-to-AgIII aryl transfer; and iv) ulterior reductive elimination of benzotrifluorides from an [aryl-AgIII -CF3 ] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K]+ [AgIII (CF3 )4 ]- (K-1), [(bpy)AgIII (CF3 )3 ] (2) and [(phen)AgIII (CF3 )3 ] (3), is described. The utility of 3 in cross-coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [AgIII (aryl)(CF3 )3 ]- intermediates. This work breaks with old stereotypes and misconceptions regarding the inability of Ag to undergo cross-coupling by itself.

Theoretical Approaches To Estimating Homolytic Bond Dissociation Energies of Organocopper and Organosilver Compounds

Although organocopper and organosilver compounds are known to decompose by homolytic pathways among others, surprisingly little is known about their bond dissociation energies (BDEs). In order to address this deficiency, the performance of the DFT functionals BLYP, B3LYP, BP86, TPSSTPSS, BHandHLYP, M06L, M06, M06-2X, B97D, and PBEPBE, along with the double hybrids, mPW2-PLYP, B2-PLYP, and the ab initio methods, MP2 and CCSD(T), have been benchmarked against the thermochemistry for the M-C homolytic BDEs (D(0)) of Cu-CH(3) and Ag-CH(3), derived from guided ion beam experiments and CBS limit calculations (D(0)(Cu-CH(3)) = 223 kJ·mol(-1); D(0)(Ag-CH(3)) = 169 kJ·mol(-1)). Of the tested methods, in terms of chemical accuracy, error margin, and computational expense, M06 and BLYP were found to perform best for homolytic dissociation of methylcopper and methylsilver, compared with the CBS limit gold standard. Thus the M06 functional was used to evaluate the M-C homolytic bond dissociation energies of Cu-R and Ag-R, R = Et, Pr, iPr, tBu, allyl, CH(2)Ph, and Ph. It was found that D(0)(Ag-R) was always lower (~50 kJ·mol(-1)) than that of D(0)(Cu-R). The trends in BDE when changing the R ligand reflected the H-R bond energy trends for the alkyl ligands, while for R = allyl, CH(2)Ph, and Ph, some differences in bond energy trends arose. These trends in homolytic bond dissociation energy help rationalize the previously reported (Rijs, N. J.; O'Hair, R. A. J. Organometallics2010, 29, 2282-2291) fragmentation pathways of the organometallate anions, [CH(3)MR](-).

Printing Radio Frequency Identification (RFID) Tag Antennas Using Inks Containing Silver Dispersions

Rotary letterpress and flexographic printing were investigated for their potential use in making electrically conductive structures. A variety of test patterns were designed to determine some of the printing process capabilities. Antennas for radio frequency identification tags were printed using these techniques. The ink used in this study was a dispersion of silver flakes, and organosilver compounds in an organic vehicle. A variety of printing parameters (inking time, inking speed, printing speed, and printing force) were studied. The printed test patterns and antennas were characterized by a profilometry, electron and optical microscopy, and electrical measurements.

ChemInform Abstract: First Evidence for the Use of Organosilver Compounds in Pd‐Catalyzed Coupling Reactions; a Mechanistic Rationale for the Pd/Ag‐Catalyzed Enyne Synthesis?

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First evidence for the use of organosilver compounds in Pd-catalyzed coupling reactions; a mechanistic rationale for the Pd/Ag-catalyzed enyne synthesis?

Silver acetylides have been prepared and used in Pd-catalyzed coupling reactions. Enynes have thus been obtained in good yields. This work demonstrates that organosilver compounds could enter the Pd catalytic cycle; it also supports the role of silver acetylides as intermediates in the new Pd/Ag-catalyzed coupling reaction.

Construction and Conductivity of W-Type Sandwich Silver(I) Polymers with Pyrene and Perylene.

Two organosilver(I) compounds of pylene and perylene presented here exhibit an unusual tetra-η2-coordination, bridging four metal centers and leading to W-type sandwich polymeric chains and sheets. Both compounds, show typical radical cation ESR signals upon irradiation with light or iodination.

ChemInform Abstract: A Novel Ethynylation of Pyridines by Reissert‐Henze Type Reaction.

AbstractPyridine 1‐oxide (I) is converted to the benzoyloxypyridinium salt (III) which is directly coupled with the phenylmetals (IV) or the organosilver compounds (VI) to produce the 1‐ethynylpyridines (V) or (VII).

Acute toxicity of some silver salts of sulfonamides in mice and the efficacy of penicillamine in silver.

The silver salt of 2-metanilamido-5-chloropyrimidine (AgMCP) and the sodium, amminosilver and trimethylphosphite-silver salts of 3',5'-dichlorobenzenesulfonanilide (NaDBS, AgNH3DBS and AgP(OCH3)3DBS were synthesized as possible antibiotic of antiparasitic drugs. All the organosilver compounds were extremely water-insoluble. For animal studies these, and other reference compounds, were given as fine suspensions in an Emulphor-safflower oil mixture. The ip LD50's in mice in mmol/kg were: 1.67 for NaDBS, 0.22 for silver acetate (AgAc), 0.15 for AgP(OCH3)3DBS, 0.13 for AgMCP and 0.10 for AgNH3DBS. When given by mouth, 15 mmol AgAc/kg produced a high mortality, but none of the organosilver compounds caused death in maximal doses (1.9 to 2.6 mmol/kg) that could be given based on considerations of total volume and stability of the suspension. All the silver compounds, including AgAc, produced a similar toxic syndrome with initial hyperexcitability, ataxia, central nervous depression, labored breathing, loss of righting reflex and death. Most deaths occurred between 12 and 24 hours after dosing. In contrast, animals given NaDBS often died within 3 hours although the major signs were very similar to those produced by the silver compounds. When given ip as a single dose 30 minutes after AgAc, D-penicillamine was effective in reducing mortality, but it had no effect on the mortality of the organosilver compounds. Histological studies revealed similar patterns of silver deposition, especially in the liver and kidneys, at 6, 18 and 24 hours after the organosilver compounds and after AgAc. We conclude that the presence of silver contributes significantly to the acute toxicity of these sulfonamides although they may dissociate free silver less readily than does AgAc.

Perfluoro organic compounds of silver

Abstract Non fluorinated organo silver compounds are thermally unstable. In contrast fluorinated organo silver compounds are thermally more stable, the stability increasing with perfluoro aromatic counterparts rather than perfluoro aliphatic systems. The synthesis of pentafluorophenyl silver can be done by several methods: Similar results are obtained using complexes of silver pentafluorobenzoate with α, α′-Dipyridyl or o-phenanthroline as starting compounds. The C 6 F-Ag-compounds react as C 6 F 5 -transferring systems. Their structur seems to consist of clusters, the highest mass number found corresponding to [Ag 4 (C 6 F 5 ) 3 ] + . On thermal degradation [Ag 2 C 6 F 5 ] n seems to be formed. Increased thermal stability is shown by Paratetrafluorophenylene disilver, which is formed by decarboxylation of silver tetrafluoro terephthalate. Although insoluble in organic solvents it can be reacted in suspension yielding 1,4 derivatives of tetrafluorobenzene. All complexes of silver tetrafluoro phthalate are degraded during decarboxylation with the formation of Para-tetrafluorophenylene disilver.

Some reactions of organosilver compounds of chloroferrocene

1. The reaction of 1-(1′-chloroferrocenyl)silver and 1-(2-chloroferrocenyl)silver with iodine gives, respectively, 1′-chloro-1-iodoferrocene and 1-chloro-2-iodoferrocene, and the corresponding dichlorodiferrocenyls. 2. The reaction of the organosilver compounds of chloroferrocene with iodobenzene gave, respectively, 1′-chloro-1-phenylferrocene and 1-chloro-2-phenylferrocene, which were reacted with copper phthalimide and copper acetate.

Stabilization of organosilver(I) compounds, and their application in organic synthesis

The favourable influence of lithium bromide on the thermal stability of organosilver(I) compounds is described. The stabilized silver(I) compounds have been brought into reaction with conjugated enynes; the regiochemistry of the reactions appears to depend on steric factors. A comparison is presented of the behaviour of the silver(I) and the corresponding copper(I) reagents in this reaction.

Alkylidentriphenylphosphoran-komplexe von kupper(I)- und silber(I)-chlorid: I. [formula omitted] komplexe

Ylide complexes of the type [(C 6H 5) 3PCHRMCHRP(C 6H 5) 3]Cl (M = Cu, Ag) have been obtained from the reaction of methylene, ethylidene- and isobutylidene-triphenylphosphorane with CuCl and AgCl. These organocopper and organosilver compounds are of surprisingly high thermal stability. In the 1H, 13C and 31P NMR spectra of the silver compound (R = H) the spin—spin interactions 1HC 107,109 Ag, 31PC 107,109 Ag, and for the first time, 13C 107,109 Ag could be detected.

ChemInform Abstract: CARBON DIOXIDE INSERTION INTO ORGANOCOPPER AND ORGANOSILVER COMPOUNDS

AbstractAus Phenylacetylen (I) und der Kupferverbindung (II) wird das Kupferacetylid (III) hergestellt, das durch Behandlung mit Tri‐n‐butyl‐phosphin in Tetrahydrofuran bei 80°C, Umsetzung mit Kohlendioxid sowie anschließende Methylierung in den Phenylpropiolsäuremethylester (IV) umgewandelt wird.

Carbon dioxide insertion into organocopper and organosilver compounds

Carbon dioxide insertions into organocopper and organosilver compounds occur in the presence of σ-donor ligands such as Bun3 and ButNC which increase the carbanionic reactivity of the carbanionic reactivity of the organometallics.

Stable arylsilver compounds containing dimethylamino, (dimethylamino)methyl or methoxy groups at the aryl nucleus

The following organosilver compounds have been prepared from the corresponding lithium compounds and silver bromide : {2-[(dimethylamino)methyl]phenyl}silver, {2-[(dimethylamino)methyl]phenyl}silver·silver bromide, bis{[2-(dimethylamino)phenyl]silver} · silver bromide, (2,6-dimethoxyphenyl)silver and (2,4,6-trimethoxyphenyl)silver. These substituted phenylsilvers, which have been characterized by elemental analysis, mol. wt. determinations, IR and PMR spectroscopy and by degradation reactions, show greater thermal, oxidative and hydrolytic stability than phenylsilver. In general the compounds decompose between 100° and 200° and react slowly with oxygen and water.

A new type of σ-bonded organosilver compound: [Ag–C(OR)= NAr]3

Reaction of alcoholic KOH with (ArNC)AgCI gives σ-bonded organosilver compounds [Ag–C(OR)= NAr]3, which undergo metathesis with chloro-complexes of AuI, HgII, and PtII to give σ-bonded alkyl complexes of these metals.