Grafting a homogeneous transition metal catalyst onto a silicon AFM probe: a promising strategy for chemically constructive nanolithography

International audienceWe report a novel approach to chemically selective lithography using an atomic force microscope (AFM) probe with immobilized homogeneous catalyst, potentially giving access to diverse nanoscale transformations of the surface-bound functional groups. This new concept was proven for the local epoxidation of an alkene-terminated self-assembled monolayer on silicon using H2O2 as an oxidant and a catalytic silicon AFM tip charged with manganese complexes with 1,3,7-triazacyclononane type ligands

Editorial overview: Smart use of metal reagents unlocks greener organic synthesis

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Carbenes and phosphonium ylides: a fruitful association in coordination chemistry

International audienceAmong a plethora of σ-donor ligands available, carbon-centered ones have become essential, in particular with the emergence of N-heterocyclic carbenes (NHCs), positioning themselves as credible alternatives to traditional nitrogen- and phosphorus-based systems. Phosphonium ylides representing another class of neutral η1-bonded carbon ligands have also been shown to act as effective Lewis bases. Considering the intrinsic features of the carbene and phosphonium ylide ligands, similar in terms of electronic properties, but different in terms of bonding mode, the design of hybrid systems combining these two types of carbon functionalities appeared to be a natural and exciting challenge. This Perspective comprehensively covers the chemistry of such ligand architectures from synthesis and fundamental aspects to catalytic applications

Binuclear Cu(I) and Mn(0) Complexes with a Tridentate Pyridine-NHC-Phosphane Ligand in a µ-κ 2 Ĉ,N -M;κ 1 P -M Coordination Mode

International audienceThe reaction of a non-symmetrical pyridine-NHC-phosphane (NĈP) ligand – generated in situ upon the deprotonation of the corresponding imidazolium salt – with equimolar amount of [Cu(NCMe)4](BF4) or Mn2(CO)10 leads to the formation of bimetallic complexes [Cu2(NĈP)2(NCMe)](BF4)2 and [Mn2(CO)7(NĈP)], respectively, in which the tridentate ligand exhibits an unusual µ-κ2Ĉ,N-M;κ1P-M coordination mode. According to NMR spectroscopy and mass spectrometry, the binuclear copper complex is in equilibrium in MeCN solution with two mononuclear species, namely [Cu(κ2Ĉ,P-NĈP)2](BF4) and [Cu(κ3-N,Ĉ,P-NĈP)(NCMe)](BF4)

Nitrogen Fixation by Manganese Complexes – Waiting for the Rush?

International audienceManganese is currently experiencing a great deal of attention in homogeneous catalysis as a sustainable alternative to platinum group metals due to its abundance, affordable price and low toxicity. While homogeneous nitrogen fixation employing well-defined transition metal complexes has been an important part of coordination chemistry, manganese derivatives have been only sporadically used in this research area. In this contribution, the authors systematically cover manganese organometallic chemistry related to N2 activation spanning almost 60 years, identify apparent pitfalls and outline encouraging perspectives for its future development

Manganese – new prominent actor in transfer hydrogenation catalysis

International audienceTransfer hydrogenation processes catalyzed by manganese organometallic complexes are comprehensively reviewed. The reaction scope includes the reduction of aldehydes, ketones, imines, polyaromatic nitrogen heterocycles, esters, nitriles and semi-hydrogenation of internal alkynes. Special attention is devoted to ligand design for Mn-catalyzed asymmetric transfer hydrogenation of prochiral ketones leading to enantiomerically-enriched alcohols

Half‐Sandwich Manganese Complex Bearing Fused Oxazoline‐NHC Ligand: Conformational Analysis and Evaluation in Asymmetric Ketone Hydrosilylation

International audienceThe first manganese complex bearing a chiral N-heterocyclic carbene (NHC) ligand was prepared and studied by spectroscopic methods and X-ray diffraction. While IR spectroscopy revealed the existence of two isomers in solution with distinct νCO band patterns, DFT calculations indicated that these isomers correspond to rotamers around the Mn−NHC bond and their different spectroscopic properties were rationalized by the occurrence of attractive π(C=C)⋅⋅⋅π*(C≡O) or σ(C−H)⋅⋅⋅π*(C≡O) intramolecular interligand interactions. The evaluation of this complex in catalytic hydrosilylation of acetophenone using Ph2SiH2 under UV irradiation led to the formation of the corresponding (R)-alcohol with low enantioselectivity

Manganese catalyzed reductive amination of aldehydes using hydrogen as a reductant

International audienceA one-pot two-step procedure was developed for the alkylation of amines via reductive amination of aldehydes using molecular dihydrogen as a reductant in the presence of a manganese pyridinyl-phosphine complex as a pre-catalyst. After the initial condensation step, the reduction of imines formed in situ is performed under mild conditions (50-100 degrees C) with 2 mol% of catalyst and 5 mol% of tBuOK under 50 bar of hydrogen. Excellent yields (>90%) were obtained for a large combination of aldehydes and amines (40 examples), including aliphatic aldehydes and amino-alcohols

Cationic PCP and PCN NHC Core Pincer-Type Mn(I) Complexes: From Synthesis to Catalysis

International audienceThe coordination chemistry of NHC core pincer-type PCP and PCN ligands with Mn(I) center was systematically investigated. The reaction of [Mn(CO)5Br] with free carbenes, conveniently prepared from the corresponding imidazolium salts and a strong base, lead to the initial formation of bidentate fac-[MnBr(CO)3(κ 2 P,C,L)] complexes bearing a pending phosphine or pyridine donor extremity (L), which upon bromide abstraction, afford cationic [Mn(CO)3(κ 3 P,C,L)](OTf) derivatives exhibiting a meridional or a facial coordinating geometry of tridentate NHC core ligand depending on its relative flexibility. All bi-and tridentate Mn(I) complexes were characterized by X-ray diffraction analysis. The impact of the tridentate ligand structure on catalytic performance was illustrated in the Mn-catalyzed hydrogenation of acetophenone revealing fac-[Mn(CO)3(κ 3 P,C,N)](OTf) based on a 5,6-membered metallacyclic architecture to be the most active, thus evidencing the role of the pyridine arm lability in the catalytic cycle