C−C and C−N Couplings Following Hydride Addition on Isocyanide Cyclopolyenyl Dimolybdenum Complexes to Give Tethered Aldimine and Aminocarbene Derivatives

Abstract

Reaction of [Mo Cp (μ-κ :κ ,η -PMes*)(CO) ] with S or Se followed by protonation with [H(OEt ) ](BAr' ) gave the cationic derivatives [Mo Cp {μ-κ :κ ,η -EP(C H tBu )}(CNR)(CO) ](BAr' ) (E=S; R=tBu, iPr, Ph, 4-C H OMe, Xyl; or E=Se; R=tBu; Ar'=3,5-C H (CF ) ). Reaction of the latter with K[BHsBu ] yielded the aldimine complexes [Mo Cp {μ-κ :κ ,η -SP(C H tBu (CHNR))}(CO) ] and their aminocarbene isomers [Mo Cp {μ-κ :κ ,η -SP(C H tBu (NRCH))}(CO) ] (R ≠ Xyl), following C-C and C-N couplings, respectively. Monitoring of these reactions revealed that the initial H attack takes place at a Cp ligand to give cyclopentadiene intermediates [Mo Cp{μ-κ :κ ,η -SP(C H tBu )}(η -C H )(CNR)(CO) ], which then undergo C-H oxidative addition to give the hydride isomers [Mo Cp {μ-κ :κ ,η -SP(C H tBu )}(H)(CNR)(CO) ]. In turn, the latter rearrange to give the aldimine and aminocarbene complexes. DFT calculations revealed that the hydride intermediates first undergo migratory insertion of the isocyanide ligand into the Mo-H bond to give unobservable formimidoyl intermediates, which then evolve either by nucleophilic attack of the N atom on the C ring (C-N coupling) or by migratory insertion of the formimidoyl ligand into the C ring (C-C coupling). Our data suggest that increasing the size of the substituent R at the isocyanide ligand destabilizes the aldimine isomer to a greater extent, thus favoring formation of the aminocarbene complex.

Electrochemical Characterization of Activated Carbon to Assess the Electro-Sorption of Trivalent Chromium

“…[13] As can be observed, above, Table II, pHZPC are close between the values found versus the reported in the bibliography. In the cases that pH overcome the reported values, could be due to the functional groups ionization (carboxylic and phenolic groups) and modified by H + and OHpresences [12]. Negative potential, refers the possibility to adsorb cations, cause the attraction of charged particles in an opposite charge versus the surface, that mean, positive, as it is the case of the ion of interest, trivalent chromium, which according to the diagrams of predominance species at the pH, at which the solution is (4.0), corresponds to CrOH 2+ .…”

Construction of Two-Faced (Hetero)hydrocarbyl Diiron Complexes Mediated by the Interplay of Ligands

“…Dimetallic complexes featuring two adjacent metal centers constitute unique systems in coordination chemistry, in that such a dimetallic core is the simplest framework which benefits from cooperative effects, enabling peculiar reactivity patterns (especially on bridging ligands) otherwise not viable on monometallic complexes. − Thus, dimetallic complexes have been widely investigated as convenient models to clarify and develop chemical transformations mediated by more complex structures wherein the metal–metal synergy plays a key role, such as natural enzymes and metal surfaces. , In this setting, the interest in the reactivity of hydrocarbyl ligands, bridging coordinated in dinuclear metal complexes, ranges from the elucidation of the mechanisms of carbon–carbon bond formation processes (e.g., the Fischer–Tropsch synthesis), − the metal-mediated synthesis of organic compounds, , new organometallic motifs not accessible from conventional procedures, − and the formation of complexes with functionalized ligands supplying useful properties for applications in catalysis, electronics, and medicinal chemistry. − The huge and urgent demand for the development of sustainable synthetic methodologies renders diiron complexes an ideal choice to explore novel organometallic reaction pathways based on the abundance and environmental benignity of iron. ,− …”