Formation of C−X Bonds Through Stable Low-Electron Count Cationic Pt(IV) Alkyl Complexes Stabilized by N-Heterocyclic Carbenes

Cationic five-coordinate Pt(IV) alkyl complexes stabilized by bulky N-heterocyclic carbenes have been isolated and fully characterized. Related species have been postulated as key intermediates in carbon–heteroatom coupling reactions and most particularly in Shilov-type chemistry. The alkyl groups exhibit a pronounced electrophilic character and can undergo nucleophilic addition of pyridine, bromide, or iodide to form new carbon–heteroatom bonds. Nevertheless, direct reductive coupling to form C–X bonds can be operative in the absence of an external nucleophile source.Ministerio de Ciencia, Innovación y Universidades CTQ2013-45011Junta de Andalucía FQM-212

Dynamic Pd(II) /Cu(I) Multimetallic Assemblies as Molecular Models to Study Metal-Metal Cooperation in Sonogashira Coupling

Cooperation between two different metals plays a crucial role in many synergistic catalytic reactions, such as the Sonogashira C-C cross-coupling reaction, where an interaction between the Pd and Cu centers is proposed in the transmetalation step. Although several heterobimetallic Pd/Cu complexes were proposed as structural models of the active species in Sonogashira coupling, the detailed understanding of the metal-metal cooperation in transmetalation is still lacking in current systems. In this work, we report a stepwise and systematic approach to building heteromultimetallic Pd/Cu assemblies as a tool to study metal-metal cooperativity. We obtained fully characterized Pd/Cu multimetallic assemblies that show reactivity in alkyne activation, formation of catalytically relevant aryl/acetylide species, and C-C elimination, serving as functional models for Sonogashira reaction intermediates. The combined experimental and DFT studies highlight the importance of ligand-controlled coordination geometry, metal-metal distances and dynamics of the multimetallic assembly for transmetalation step

Proton-responsive naphthyridinone-based RuII complexes and their reactivity with water and alcohols

We report the synthesis and reactivity of RuII complexes with a new naphthyridinone-substituted phosphine ligand, 7-(diisopropylphosphinomethyl)-1,8-naphthyridin-2(1H)-one (L-H), which contains two reactive sites that can potentially be deprotonated by a strong base: an NH proton of naphthyridinone and a methylene arm attached to the phosphine. In the absence of a base, the stable bis-ligated complex Ru(L-H)2Cl2 (1) containing two NH groups in the secondary coordination sphere is formed. Upon further reaction with a base, a doubly deprotonated, dimeric complex is obtained, [Ru2(L*-H)2(L)2] (2), in which two of the four ligands undergo deprotonation at the NH (L), while the other two ligands are deprotonated at the methylene groups (L*-H) as confirmed by an X-ray diffraction study; intramolecular hydrogen bonding is present between the NH group of one ligand and an O-atom of another ligand in the dimeric structure, which stabilizes the observed geometry of the complex. Complex 2 reacts with protic solvents such as water or methanol generating aqua Ru(L)2(OH2)2 (3) or methanol complexes Ru(L)2(MeOH)2 (4), respectively, both exhibiting intramolecular H-bonded patterns with surrounding ligands at least in the solid state. These complexes react with benzyl alcohols to give aldehydes via base-free acceptorless dehydrogenation

T-Shaped Platinum(II) Complexes Stabilised by Bulky N-Heterocyclic Carbene Ligands

5 páginas, 3 figuras, 5 esquemas.Pt to a T! Treating bulky N-heterocyclic carbene (NHC) ligands with [PtMe3I]4 results in rapid elimination of ethene and formation of [PtMeI(NHC)2] complexes. These complexes are suitable materials for the synthesis of T-shaped platinum(II) complexes stabilised by agostic interactions. X-ray structure determination of one of these complexes shows a rather long ζ agostic interaction.Financial support from the Junta de Andalucía (project no. FQM-3151) and the Spanish Ministerio de Ciencia e Innovación (projects CTQ2007-62814 and CONSOLIDER-INGENIO 2010 CSD2007-00006, FEDER support) is acknowledged. O.R.-W. thanks the Spanish Ministerio de Ciencia e Innovación for a research grant

MnI complex redox potential tunability by remote lewis acid interaction

In this work we provide direct experimental evidence on the correlation of remote interactions between a newly synthesized MnI-complex (1) and different alkali cations with redox potential tuning. Furthermore we report the electrochemical behavior of 1 towards carbon dioxide, including the effects of added alkali salts using cyclic voltammetry

A binuclear cobalt complex for molecular CO2_2 electrocatalysis

A pyrazole–based ligand substituted with terpyridine groups at the 3 and 5positions has been synthesized to form the dinuclear cobalt complex 1, that electrocatalytically reduces carbon dioxide (CO$_2$) to carbon monoxide (CO) in the presence of Brønsted acids in DMF. Chemical, electrochemical and UV–vis spectro–electrochemical studies under inert atmosphere indicate a single 2 electron reduction process of complex 1 at first, followed by a 1 electron reduction at the ligand. Infrared spectro–electrochemical studies under CO$_2$ and CO atmosphere allowed us to identify a reduced CO–containing dicobalt complex which results from the electroreduction of CO$_2$. In the presence of trifluoroethanol (TFE), electrocatalytic studies revealed single–site mechanism with up to 94 % selectivity towards CO formation when 1.47 M TFE were present, at –1.35 V vs Saturated Calomel Electrode in DMF (0.39 V overpotential). The low faradaic efficiencies obtained (<50%) are attributed to the generation of CO–containing species formed during the electrocatalytic process, which inhibit the reduction of CO$_2$

Electrocatalytic CO2 reduction with a binuclear bis‐terpyridine pyrazole‐bridged cobalt complex

International audienceA pyrazole–based ligand substituted with terpyridine groups at the 3 and 5 positions has been synthesized to form the dinuclear cobalt complex 1 , that electrocatalytically reduces carbon dioxide (CO2) to carbon monoxide (CO) in the presence of Brønsted acids in DMF. Chemical, electrochemical and UV–vis spectro–electrochemical studies under inert atmosphere indicate pairwise reduction processes of complex 1 . Infrared spectro–electrochemical studies under CO2 and CO atmosphere are consistent with a reduced CO–containing dicobalt complex which results from the electroreduction of CO2 . In the presence of trifluoroethanol (TFE), electrocatalytic studies revealed single–site mechanism with up to 94% selectivity towards CO formation when 1.47 M TFE were present, at –1.35 V vs Saturated Calomel Electrode in DMF (0.39 V overpotential). The low faradaic efficiencies obtained (<50%) are attributed to the generation of CO–containing species formed during the electrocatalytic process, which inhibit the reduction of CO2

Ruthenium Nanoparticles Stabilized by N-Heterocyclic Carbenes: Ligand Location and Influence on Reactivity

NHCs go nano: Ruthenium nanoparticles were formed from (cyclooctadiene)(cyclooctatriene)ruthenium(0) and stabilized by N-heterocyclic carbenes (NHCs). Solid-state NMR spectroscopy revealed both the coordination of the NHC ligands on the surface of the particles and their surface reactivity.We thank V. Collière and L. Datas (UPS-TEMSCAN) and P. Lecante (CNRS-CEMES) for TEM/HR-TEM and WAXS facilities, respectively. CNRS and ANR (Siderus project ANR-08-BLAN-0010-03) are also thanked for financial support. P.L. is grateful to the Spanish Ministerio de Educación for a research contract. Financial support from the Junta de Andalucía (project no. FQM-3151) and the Spanish Ministerio de Ciencia e Innovación (projects CTQ2010-17476 and CONSOLIDER-INGENIO 2010 CSD2007-00006, FEDER support) is acknowledged. O.R.-W. thanks the Spanish Ministerio de Ciencia e Innovación for a research grant.Peer Reviewe