Double C-H activation in a Rh-NHC complex leading to the isolation of a 14-electron Rh(III) complex

The solvent-dependent interaction of ItBu with a Rh(I)-olefin complex leads to the isolation of two precursors en route to a unique double cyclometalation process. Abstraction of the chloride ligand from the resulting complex enables the isolation of a "bare" 14-electron Rh(III) complex.

Double C−H Activation in a Rh−NHC Complex Leading to the Isolation of a 14-Electron Rh(III) Complex

The solvent-dependent interaction of ItBu with a Rh(I)-olefin complex leads to the isolation of two precursors en route to a unique double cyclometalation process. Abstraction of the chloride ligand from the resulting complex enables the isolation of a "bare" 14-electron Rh(III) complex.

Reactivity of a N-heterocyclic carbene, 1,3-di-(1-adamantyl) imidazol-2-ylidene, with a pseudo-acid: structural characterization of Claisen condensation adduct

The reactivity of a N-heterocyclic carbene (NHC) with a pseudo-acid (ester in this case) is described. The product results from an unusual C-H bond activation. The structure of the product has been established by a single crystal diffraction study.

Stable, three-coordinate Ni(CO)(2)(NHC) (NHC = N-heterocyclic carbene) complexes enabling the determination of Ni-NHC bond energies

The synthesis and characterization of three- and four-coordinate Ni(CO)n(NHC) (n = 2, 3; NHC = N-heterocyclic carbene) complexes are reported. Reactions with CO of the Ni(CO)2(NHC) complexes lead to the quantitative formation of Ni(CO)4. Investigation of this reaction under equilibrium conditions allows for the determination of Ni-NHC bond dissociation energies.

The gossypol-cyclododecanone (1/2) inclusion complex

Gossypol and cyclododecanone crystallize at room temperature as an inclusion complex in a 1:2 molar ratio. This complex, viz. 1,1',6,6',7,7'-hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2'-binaphthalene-8,8'-dicarboxaldehyde-cyclododecanone (1/2), C(30)H(30)O(8).2C(12)H(22)O, is unusual in that there is limited intermolecular hydrogen bonding within the structure. Each cyclododecanone molecule accepts a hydrogen bond from a gossypol molecule, but there are no gossypol-to-gossypol hydrogen-bond interactions. The gossypol molecules form a framework structure enclosing channels, and the cyclododecanone molecules lie in these channels. In terms of the number of non-H guest atoms, this is the largest gossypol inclusion complex reported to date.

Synthesis, characterization, and catalytic activity of N-heterocyclic carbene (NHC) palladacycle complexes

Palladacycle dimers possessing bridging halides can be easily cleaved by using N-heterocyclic carbenes (NHCs) to generate novel monomeric complexes. The structure of one of these was determined by single-crystal diffraction study and consists of a square-planar coordination around the palladium center where the NHC ligand is trans to the amine of the palladacycle. The complex was found to be equally active in aryl amination and alpha-arylation of ketones even at very low catalyst loading (0.02 mol %). Primary and secondary alkyl/arylamines are equally active partners in coupling reactions. [reaction: see text]

Crystal structure of penta-O-acetyl-beta-D-galactopyranose with modeling of the conformation of the acetate groups

The crystal structure of penta-O-acetyl-beta-D-galactopyranose was determined with Mo K(alpha) radiation at 150 K to R = 0.029. The space group is P2(1)2(1)2(1), and the unit cell dimensions are, a = 8.348, b = 9.021 and c = 25.418 A. The ring has the usual 4C(1) shape and O-6 is in the tg position as frequently observed for sugars having the axial galacto configuration at C-4. Conformations of the acetate groups were compared with those from the literature. Nearly eclipsed, 'Z' conformations are found for the ester moieties, and the torsion angles for the sequence involving the ring hydrogen, carbon, alkoxy oxygen and carbonyl carbon for both 1 and related compounds are eclipsed-to-gauche. Orientations and conformations of the acetate substituents were modeled with both MM3 molecular mechanics and various levels of quantum mechanics theory. Higher levels of theory and more complete models provided better prediction of the experimental observations.

Stereoselective syntheses of the three isomers of ethylene glycol bis(tropane-3-carboxylate)

Three epimers of ethylene glycol bis(tropane-3-carboxylate) (3alpha,3alpha'-, 3alpha,3beta'-, 3beta,3beta'-) have been synthesized by starting from 3-tropinone. 3-Tropinone was converted into the corresponding enol triflate and then subjected to palladium-catalyzed alkoxycarbonylation to provide the key intermediate methyl trop-2-ene-3-carboxylate in good yield. Stereoselective routes were developed to afford the three stereoisomers of ethylene glycol bis(tropane-3-carboxylate).