Structural Chemistry of Copper(I) and Silver(I) Complexes with Triisopropylphosphane Sulfide, Selenide and Telluride Ligands

Phosphanchalkogenide sind von Bedeutung für die Koordination von Schwermetallen und den Aufbau und Abbau von Metallchalchogenid-Clustern (z. B. Fenske-Clustern), deren Eigenschaften zurzeit viel Beachtung finden. Hinsichtlich des Pearson-Konzeptes der harten und weichen Säuren und Basen, sollten Phosphantelluride (R3P=Te) ausgezeichnete Liganden gegenüber “weichen” Schwermetallkationen sein. Trotzdem sind sehr wenige Komplexe mit Phosphantellurid-Liganden in der Literatur bekannt. Zum Studium der Eingeschaften von Trialkylphosphantelluriden gegenüber Münzmetallen in der Lösung und im Festkörper wurden die Komplexe von Triisopropylphosphanchalkogeniden mit Kupfer(I), Silber(I) und Gold(I) untersucht. R3PTe-Cu(I) und R3PTe-Au(I) Komplexe (R=Me, iPr, tBu) wurden nur als intermediäre Spezies beobachtet, während die Silber(I)-Komplexe eine größere Stabilität mit zunehmenden Donoreigenschaften der R-Gruppe und abhängig von Natur des Anions aufweisen. Mit sehr schwach Nukleophilen (SbF6-Anion) bilden sich ionische und /oder supramolekulare Strukturen, während mit zunehmender Nukleophilie molekulare Strukturen erhalten wurden. Die besseren Donoreigenschaften von Tellur verglichen mit Schwefel oder Selen sind sehr gut in Komplexen mit Silber(I)-halogeniden zu beobachten. Der iPr3PTeAgI-Komplex zeigt in der Festkörperstruktur eine Tellur-Verbrückte Struktur, während iPr3PSAgCl-Komplex eine Chlor-Verbrückte Struktur mit terminalen Phosphansulfidliganden besitzt.With regard to the Pearson concept of hard and soft acids and bases, phosphane tellurides (R3P=Te) should be excellent ligands towards “soft” heavy metal cations. Their role as sources of phosphanes and of elemental tellurium allows them to contribute to the formation and decomposition of metal telluride clusters (like Fenske-typ coinage metal chalcogenide clusters), still R3P=Te complexes are extremely rare. To study the particular properties of the trialkylphosphane telluride ligands towards coinage metals in solution and in solid state, the coordination chemistry of triisopropylphosphane chalcogenides (iPr3PS, iPr3PSe and iPr3PTe) with silver(I), copper(I) and gold(I) salts was investigated. R3PTe-Cu(I) and Au(I) complexes (R = tBu, iPr, Me) are only transient species in solution, whereas in Ag(I) case, the basicity of R groups and the nature of the anion have an important role. The stability of complexes increases with increasing of R group branching. Less nucleophilic anions (SbF6 anion) led to the formation of ionic and/or supramolecular structures, while with increasing of anions nucleophilicity ([N(SO2CH3)2] or halides anions) molecular structures are obtained. The better donor proprieties of tellurium towards sulphur or selenium can be observed in the case of complexes with silver(I) halides. In the case of complex with phosphane telluride ligand iPr3PTeAgI a tellurium-bridge structure was obtain, while the complex iPr3PSAgCl shows in solid state a chlor-bridge structure with terminal phosphane sulphide ligands

6‑Aroylated Phenanthridines via Base Promoted Homolytic Aromatic Substitution (BHAS)

Readily accessible 2-isocyanobiphenyls react with aromatic aldehydes via base promoted homolytic aromatic substitution (BHAS) to give 6-aroylated phenanthridines. Reactions occur via addition of acyl radicals to the isonitrile functionality and subsequent intramolecular BHAS of the intermediate imidoyl radicals. Initiation of the radical chain reaction is best achieved with small amounts of FeCl₃ (0.4 mol %), and the commercially available and cheap <i>t</i>BuOOH is used as the oxidant

3‑Alkylperoxy-3-cyano-oxindoles from 2‑Cyano-2-diazo‑<i>N</i>‑phenyl-acetamides via Cyclizing Carbene Insertion and Subsequent Radical Oxidation

A transition-metal-free one-pot sequence for the synthesis of 3-peroxy-substituted oxindoles from readily prepared 2-cyano-2-diazo-acetamides is reported. The two-step tandem process includes a highly efficient thermal intramolecular C–H-carbene insertion followed by a tetrabutyl­ammonium iodide (TBAI) catalyzed radical C3-peroxy-functionalization. The protocol provides easy access to a new class of 3-cyano-3-peroxy-disubstituted oxindoles. Useful transformations to amides and alcohols are demonstrated

6‑Phosphorylated Phenanthridines from 2‑Isocyanobiphenyls via Radical C–P and C–C Bond Formation

A C–P bond and a C–C bond are formed in the synthesis of 6-phosphorylated phenanthridines starting with readily prepared 2-isocyanobiphenyls and commercially available P-radical precursors. The radical cascade reaction comprises addition of an oxidatively generated P-centered radical to the isonitrile functionality and subsequent homolytic aromatic substitution. Various 6-phosphorylated phenanthridines are formed in moderate to excellent yield. In contrast to the currently intensively investigated direct arene phosphorylation, the arene core is constructed with concomitant phosphorylation using this approach

6‑Phosphorylated Phenanthridines from 2‑Isocyanobiphenyls via Radical C–P and C–C Bond Formation

A C–P bond and a C–C bond are formed in the synthesis of 6-phosphorylated phenanthridines starting with readily prepared 2-isocyanobiphenyls and commercially available P-radical precursors. The radical cascade reaction comprises addition of an oxidatively generated P-centered radical to the isonitrile functionality and subsequent homolytic aromatic substitution. Various 6-phosphorylated phenanthridines are formed in moderate to excellent yield. In contrast to the currently intensively investigated direct arene phosphorylation, the arene core is constructed with concomitant phosphorylation using this approach

CO/CO and NO/NO coupling at a hidden frustrated Lewis pair template

N-Allyltetramethylpiperidine is readily isomerized to the corresponding enamine by treatment with catalytic amounts of B(C6F5)3. It adds HB(C6F5)2 at the nucleophilic enamine carbon atom to form a C/B Lewis adduct. This reacts with two molar equivalents of carbon monoxide by selective head to tail coupling to give a five-membered C2O2B heterocycle. In contrast the enamine/HB(C6F5)2 Lewis pair reacts with two molar equiv. of nitric oxide by head to head coupling. This reaction probably proceeds via equilibrium with the corresponding vicinal N/B Lewis pair. Most products were characterized by X-ray diffraction

Tuning the Structural and Photophysical Properties of Cationic Pt(II) Complexes Bearing Neutral Bis(triazolyl)pyridine Ligands

The emission properties of a series of cationic Pt­(II) complexes bearing neutral tridentate 2,6-bis-(1<i>H</i>-1,2,3-triazol-5-yl)­pyridine and monoanionic ancillary ligands (Cl^– or CN^–) are described. By varying the substitution pattern on the 1,2,3-triazole moieties of the tridentate luminophore and the nature of the ancillary ligand, we were able to tune the intermolecular interactions between the complexes and therefore the electronic interactions between the metal centers. Indeed, all the compounds possessing Cl^– as ancillary ligand are nonluminescent at room temperature, while the complexes containing CN^– are luminescent. Interestingly, the π-accepting nature of this ancillary ligand induces Pt­(II)–Pt­(II) interactions irrespectively of bulky substitution patterns on the tridentate ligand

Synthesis of Bulky Nitroxides, Characterization, and Their Application in Controlled Radical Polymerization

This paper describes the synthesis of several highly sterical hindered alkoxyamines based on 6-membered cyclic nitroxides and their application as initiators/regulators in the controlled nitroxide-mediated radical polymerization of <i>n</i>-butyl acrylate and styrene. Rate constant <i>k</i>_d and activation energy <i>E</i>_a of the C–O bond of the novel alkoxyamines are reported. Conformational studies on the new nitroxides are performed by X-ray analysis and by DFT calculations. The polymerization of <i>n</i>-butyl acrylate can be conducted at 60 °C showing that these hindered nitroxides are highly valuable to conduct nitroxide-mediated acrylate polymerization (NMP). In addition, low temperature (50 °C) styrene polymerizations are disclosed

Tuning the Structural and Photophysical Properties of Cationic Pt(II) Complexes Bearing Neutral Bis(triazolyl)pyridine Ligands

The emission properties of a series of cationic Pt­(II) complexes bearing neutral tridentate 2,6-bis-(1<i>H</i>-1,2,3-triazol-5-yl)­pyridine and monoanionic ancillary ligands (Cl^– or CN^–) are described. By varying the substitution pattern on the 1,2,3-triazole moieties of the tridentate luminophore and the nature of the ancillary ligand, we were able to tune the intermolecular interactions between the complexes and therefore the electronic interactions between the metal centers. Indeed, all the compounds possessing Cl^– as ancillary ligand are nonluminescent at room temperature, while the complexes containing CN^– are luminescent. Interestingly, the π-accepting nature of this ancillary ligand induces Pt­(II)–Pt­(II) interactions irrespectively of bulky substitution patterns on the tridentate ligand

Synthesis, Physico-chemical Characterization, Crystal Structure and Influence on Microbial and Tumor Cells of Some Co(II) Complexes with 5,7-Dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

Three complexes, namely [Co(dmtp)2(OH2)4][CoCl4] (1), [Co(dmtp)2Cl2] (2) and [Co(dmtp)2(OH2)4]Cl2∙2H2O (3) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized by spectral (IR, UV-Vis-NIR), and magnetic measurements at room temperature, as well as single crystal X-ray diffraction. Complex (1) crystallizes in monoclinic system (space group C2/c), complex (2) adopts an orthorhombic system (space group Pbca), and complex (3) crystallizes in triclinic system (space group P1). Various types of extended hydrogen bonds and π–π interactions provide a supramolecular architecture for all complexes. All species were evaluated for antimicrobial activity towards planktonic and biofilm-embedded microbial cells and influence on HEp-2 cell viability, cellular cycle and gene expression