Synthesis of a square-planar rhodium alkylidene N-heterocyclic carbene complex and its reactivity toward alkenes

The first rhodium alkylidene square-planar complex stabilized by an N-heterocyclic carbene ligand, RhCl(-CHPh)(IPr)PPh3 (2; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene), has been prepared by reaction of RhCl(IPr)(PPh3)2 (1) with phenyldiazomethane and its dynamic behavior in solution studied. Treatment of 2 with alkenes results in the formation of the ¿2-olefin complexes RhCl(¿2-CH2-CHR)(IPr)PPh3 (3, R = H; 4, R = Ph; 5, R = OEt) and new olefins arising from the coupling of the alkylidene with the alkenes, likely via a metallacyclobutane intermediate

Scaling the state: Egypt in the third millennium BC

Discussions of the early Egyptian state suffer from a weak consideration of scale. Egyptian archaeologists derive their arguments primarily from evidence of court cemeteries, elite tombs, and monuments of royal display. The material informs the analysis of kingship, early writing, and administration but it remains obscure how the core of the early Pharaonic state was embedded in the territory it claimed to administer. This paper suggests that the relationship between centre and hinterland is key for scaling the Egyptian state of the Old Kingdom (ca. 2,700-2,200 BC). Initially, central administration imagines Egypt using models at variance with provincial practice. The end of the Old Kingdom demarcates not the collapse, but the beginning of a large-scale state characterized by the coalescence of central and local models

Cationic ruthenium allenylidene complexes as a new class of performing catalysts for ring closing metathesis

Cationic allenylidene ruthenium complexes [Ru=C=C=CR2(L)(Cl)(arene)]PF6 (L = PCy3, PPri3), easily prepared from RuCl2(L)(p-cymene), prop-2-yn-1-ol and NaPF6, are found to be excellent catalyst precursors for ring closing olefin metathesis

Allenylidene to Indenylidene Rearrangement in Arene-Ruthenium Complexes : a Key Step to Highly Active Catalysts for Olefin Metathesis Reactions

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Ruthenium-Catalyzed Synthesis of Functionalized Dienes from Propargylic Esters : Formal Cross-Coupling of Two Carbenes

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Cp*RuCl(COD) in Catalysis : a Unique Role in the Addition of Diazoalkane Carbene to Alkynes

International audienceThe catalytic transformations of functional alkynes with diazoalkanes in the presence of the catalyst precursor RuCl(COD)Cp* are presented. They show the unique role played by the Ru(X)Cp* moiety in catalysis and that the nature of the formed products strongly depends on the alkyne functionality. Simple alkynes generate dienes via double diazoalkane carbene addition to the triple bond. Enynes with terminal triple bond lead to alkenyl bicyclo[x.1.0]alkanes, including bicyclic aminoacid derivatives. 1,6-enynes with disubstituted propargylic carbon produce in priority alkenyl alkylidene cyclopentanes. 1,6-Allenynes offer the direct access to alkenyl alkylidene bicyclo[3.1.0]hexanes. Propargylic carboxylates lead to conjugated dienes by coupling of the diazoalkane carbene with the alkyne terminal carbon and 1,2-shift of the carboxylate. All catalytic reactions can be explained by the initial formation of the 16 electron RuCl(double bond; length as m-dashCHR)Cp* moiety giving first a 2+2 cycloaddition with the alkyne triple bond

Ruthenium-Catalyzed C−H Bond Alkylation of Arylphosphine Oxides with Alkenes: A Straightforward Access to Bifunctional Phosphorous Ligands with a Pendent Carboxylate

International audienceAn efficient approach for the fast modification of arylphosphine oxides involving ruthenium(II)-catalyzed C−H bond alkylation with functional alkenes versus alkenylation has been developed depending on the acidic reaction conditions. Using this methodology, a few examples of desymmetrization of diarylphosphine oxides has allowed the formation of phosphorus derivatives containing three different substituents. After reduction of the phosphine oxide, this method allows the formation of aryl phosphines bearing a flexible pendent carboxylate