Dispersion, solvent and metal effects in the binding of gold cations to alkynyl ligands: implications for Au(i) catalysis.

The coordination modes of the [Au(PPh3)](+) cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η(5)-C5H5)(PPh3)2([double bond, length as m-dash]C[double bond, length as m-dash]CPh{AuPPh3})](+), is obtained while addition to a gold(iii) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(i) cation is sandwiched between two gold(iii) alkynyl complexes, suggesting that coordination of multiple C-C triple bonds to gold is facile

Cyclopropenylidenes: From interstellar space to an isolated derivative in the laboratory

Lavallo V, Canac Y, Donnadieu B, Schoeller W, Bertrand G. Cyclopropenylidenes: From interstellar space to an isolated derivative in the laboratory. SCIENCE. 2006;312(5774):722-724.Like many of the molecular species that have been detected in the interstellar medium, the singlet carbene cyclopropenylidene (C3H2) has been presumed to be too unstable to isolate in the laboratory. However, by appending pi-electron-donating amino groups to the triangular skeleton, we prepared a cyclopropenylidene derivative that is stable at room temperature. In contrast to previously isolated carbenes, this compound does not require a heteroatom adjacent to the electron-deficient carbon to confer stability. Despite the presence of amino groups, the geometric parameters of the cyclic skeleton, revealed by x-ray crystallography, are only slightly perturbed relative to those of the calculated structure of unsubstituted cyclopropenylidene. Stable cyclopropenylidene derivatives might thus serve as models for a better understanding of the formation of carbon-bearing molecules in the interstellar medium

Synthesis, reactivity, and ligand properties of a stable alkyl carbene

Lavallo V, Mafhouz J, Canac Y, Donnadieu B, Schoeller W, Bertrand G. Synthesis, reactivity, and ligand properties of a stable alkyl carbene. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 2004;126(28):8670-8671

First examples of diazepanylidene carbenes and their late-transition-metal complexes

The synthesis of the novel seven-membered N-heterocyclic carbene (NHC) 1,3-dicyclohexyl-1,3-diazepan-2-ylidene (3) and its 5,6-dioxolane derivative 4 is reported and their coordination chemistry with Rh(I), Ir(I), and Pt(0) discussed. The M(cod)(3)Cl, where M = Rh and Ir, complexes display a high rotation barrier at room temperature about the M-CNHC bond, whereas for the M(CO)2(3)Cl and Pt(nbe)2(3) complexes rapid rotation of the carbene ligand is observed at ambient temperature. The infrared (CO) values of the Rh(I) and Ir(I) derivatives M(CO)2(3)Cl give a measure of the donor ability of the new carbene ligands. The crystal structures of the amidinium salts 3·HPF6 and 4·HPF6 together with those of M(cod)(3)Cl [M = Rh, Ir], Ir(cod)(4)Br, Ir(CO)2(3)Cl, and Pt(nbe)2(3) are reported. Both the salts and the coordinated carbene ligands exhibit extremely large NCN angles; for the complexes the angles are in the range 115.5(3) [Pt(3)] to 122(11) [Ir(4)]

Palladium(II) pyrazolin-4-ylidenes: Substituent effects on the formation and catalytic activity of pyrazole-based remote NHC complexes

10.1021/om8010849Organometallics2892778-2786ORGN