Antoine Baceiredo

Cyclic (Amino)(bis(ylide))carbene as an Anionic Bidentate Ligand for Transition Metal Complexes

The 3-(triphenylphosphonio)-N-(2,6-diisopropylphenyl)pyrrole reacts with 2 equiv of methyllithium to afford a lithium adduct in which a cyclic (amino)[bis(ylide)]carbene, a novel type of NHC, acts as a 1,4-bidentate ligand via the carbene center and the exocyclic ylidic carbon. This species readily undergoes transmetalation reactions, which allows for the synthesis of a variety of transition-metal complexes.

Stable phosphonium sila-ylide with reactivity as a sila-Wittig reagent.

The silicon congeners of well-known phosphonium ylides have been considered only as short-lived reactive intermediates. We successfully synthesized a remarkably stable phosphonium sila-ylide. Its X-ray structure reveals a long Si-P bond and a strongly pyramidalized silicon center, indicating a very weak P-Si pi interaction. In addition, it exhibits an alpha,beta-ambiphilic character with a nucleophilic silicon center, similar to its carbon-congener phosphonium ylides. This property of the phosphonium sila-ylide allows its use as a sila-Wittig reagent with carbonyl derivatives.

Synthesis and Characterization of an Isolable Base‐Stabilized Silacycloprop‐1‐ylidene

Strained but stable: An isolable silacycloprop-1-ylidene stabilized by intramolecular complexation with an iminophosphorus ylide fragment was successfully synthesized and fully characterized. The formation of this small highly strained cyclic silylene involves an unprecedented Si(IV)→Si(II) rearrangement under very mild conditions.

Activation of CO2 and SO2 by Boryl(phosphino)carbenes

The stable boryl(phosphino)carbene 1 can cleave small organic dioxide molecules. With CO2 and SO2, 1 gives, respectively, the phosphacumulene ylide [Mes(i Pr2N)B‐O‐P(CCO)(Ni Pr2)Mes] (see scheme and structure) and boryl(phosphoryl)sulfine [Mes(i Pr2N)B‐C(SO)‐P(O)(Ni Pr2)Mes] which have been structurally and spectroscopically characterized.

Borylated methylenephosphonium salts: precursors of elusive boryl(phosphino)carbenes.

The synthesis of a new family of boryl-substituted methylenephosphonium derivatives, the phosphorus analogues of iminium salts, has been developed. They were used in the preparation of the first stable boryl(phosphino)carbene, which has been fully characterized by NMR spectroscopy and X-ray crystallography. Density functional theory calculations indicate that these carbenes can be classified as push-pull carbenes with a relatively small singlet-triplet energy gap.

Photolytic rearrangement of phosphorus azide : evidence for a transient metaphosphonimidate.

Durch Photolyse von Diphenyl-phosphorylazid (I) entsteht intermediar das Metaphosphonimidat (II), das in Abwesenheit von reaktiven Komponenten zum Dimeren (III) abreagiert.

An Isolable Mixed P,S‐Bis(ylide) as an Asymmetric Carbon Atom Source

The transformation of molecules by introduction of atomic elements is one of the most fundamental reactions in chemistry. Indeed, the reactions of atomic hydrogen (reduction, hydrogenation) and oxygen (oxidation, epoxidation) are exceedingly important in organic synthesis, and numerous reagents and catalysts for this purpose are available. In marked contrast, the manipulation of atomic elements with a higher valence number, such as nitrogen and carbon, remains a more difficult task. Although several C1 sources have been intensely investigated, only a few atomic carbon synthetic equivalents, such as unsaturated diazo derivatives I and II, have been

Synthesis and characterization of rhodium complexes with phosphine-stabilized germylenes.

The reaction of phosphine-stabilized germylenes (1a,b) with dimer complex [Rh(2)(μ-Cl)(2)(COD)(2)] leads to the corresponding phosphine-germylene-Rh(I) complexes (2a,b). Interestingly, the stability of these complexes depends strongly on the nature of the substituent of the germylene fragment. Indeed, the complex (2a) with the chloro-germylene ligand isomerizes into a metallacycle rhodium complex (3a) via germylene insertion into the Rh-Cl bond, while the complex with the phenyl-substituted germylene (2b) was isolated and represents the first stable Rh(I)-germylene complex with a Rh-Cl bond.

Non-NHCs Stable Singlet Carbene Ligands

Carbene chemistry has been tremendously developed during the last 20 years. NHC carbenes have found many applications as ligands in organometallic chemistry or as catalysts in organocatalysis. On the other hand, the so-called “non-NHC stable carbenes” have had a restrained development to date in spite of the high potential of this family of carbenes which offers many more possibilities in structure modifications, resulting in original reactivities. This chapter gives an overview over non-NHC stable singlet carbenes and their properties as ligands.

Synthesis and Ligand Properties of a Stable Five‐Membered‐Ring Vinylidenephosphorane

Over the years, the success of homogeneous catalysis can be attributed largely to the development of a diverse range of ligand frameworks that have been used to tune the behavior of the various systems. Recently, N-heterocyclic carbenes (NHCs) A (Scheme 1) have emerged as powerful ligands, largely because of their strong donor properties, which are due to the presence of a lone pair and a partially filled vacant orbital. In our search for even stronger donor ligands, we became interested in carbodiphosphoranes, especially their cyclic versions B, because, as we have learned from carbene chemistry, they lead to more robust transition-metal complexes than their acyclic congeners. We have demonstrated using the nav(CO) infrared frequency of [(L)Rh(CO)2Cl] complexes that these species, which feature a carbon formally bearing two lone pairs, were indeed stronger donors than NHCs A. Along this line, we have also reported the synthesis of acyclic and cyclic push–push bent allenes (carbodicarbenes) C, which are electronically similar to carbodiphosphoranes. These results led us to consider a mixed system D with a phosphorus–carbon ylidic bond and a carbon–carbon double bond. Interestingly, such heteroallenes have a resonance form D directly related to the previously reported push–pull allenes E and push–pull carbenes F, as shown by their resonance forms. In contrast to the numerous examples of acyclic derivatives, only one cyclic vinylidenephosphorane, stable at low temperature for a short period of time, has been described, and no crystallographic data or coordination behavior has been reported. Herein we present the synthesis, single crystal X-ray diffraction study, and ligand properties of a cyclic vinylidenephosphorane 5 that is stable at room temperature both in solution and in the solid state. The cyclic phospholium salt 4, without undesired acidic protons, was chosen as the precursor for the target vinylidenephosphorane 5. Starting from the readily available diene 1, a formal [4+1] cycloaddition with bis(diisopropyl)aminophosphenium triflate gives rise to the phospholenium salt 2 (Scheme 2). Deprotonation of 2 with NaNH2 in ammonia Scheme 1. Similarities and differences between NHCs A, carbodiphosphoranes B, push–push allenes C, vinylidenephosphoranes D, push– pull allenes E, and push–pull carbenes F.