Complexes of iridium bearing NHC (NHC ) N-heterocyclic carbene) ligands were synthesized and fully characterized. The series [(NHC)Ir(cod)Cl] were obtained by simple cleavage of [Ir(cod)Cl] 2 . The [(NHC)Ir(cod)Cl] complexes were reacted with excess carbon monoxide, leading to [(NHC)Ir(CO) 2 Cl]. The infrared carbonyl stretching frequencies of these were recorded to quantify the electronic parameter of NHC ligands. X-ray diffraction study results allow for determination of NHC steric parameters within this series. These data allow for comparison with other ligand families.

The synthesis and structural characterization of a series of palladium complexes bearing N-heterocyclic carbenes (NHC) as supporting ligands are described. The reaction of commercially available [Pd(allyl)Cl]2 and isolated or in situ generated NHC leads to monomeric palladium complexes where one NHC is bound to the metal center, as indicated by spectroscopic and single-crystal X-ray diffraction studies. The relative reactivity trend for these complexes as catalysts in aryl amination is discussed in terms of ligand steric properties, which vary as a function of imidazole-nitrogen substituents and perturbation resulting in modulation of ring planarity. The concept of buried volume is used to quantify the steric demand of each NHC in the corresponding complexes.

The catalytic formation of di- and trisubstituted ortho biaryl junctions has been achieved using a palladacylce pre-catalyst bearing a N-heterocyclic carbene ligand. This transformation is performed at room temperature in technical grade 2-propanol.

The reaction of saturated and unsaturated imidazolium salts with nickelocene in refluxing THF results in the formation of NHC complexes of general formula CpNi(NHC)Cl (NHC ) SIMes (2), IPr (3), SIPr ( 4)). This protonation of Cp 2 Ni was also tested using phosphonium salts, and the reaction of nickelocene with triethylphosphonium chloride leads to CpNi(PEt 3 )Cl ( 5). All compounds were characterized by NMR and X-ray crystallography. The catalytic activity of the NHC compounds was tested in aryl amination (Buchwald-Hartwig reaction) and in aryl halide dehalogenation reactions.

[reaction: see text] The activity of the complex (IPr)PdCl(eta2-N,C-C12H7NMe2), 1 [IPr = (N,N'-bis(2,6-diisopropylphenyl)imidazol)-2-ylidene], in the Suzuki-Miyaura cross-coupling reaction involving unactivated aryl chlorides and triflates with arylboronic acids at room temperature in technical grade 2-propanol is described. These conditions allow for the synthesis of di- and tri-ortho-substituted biaryls in very short reaction times. This complex also displays very high activity for alpha-ketone arylation and dehalogenation reactions of activated and unactivated aryl chlorides.

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The active metathesis catalyst (PCy 3 ) 2 Cl 2 Ru(3-phenylinden-1-ylidene) (4) was obtained in high yield using a simple one-pot procedure. The initial reaction of RuCl 2 (PPh 3 ) 3 with 1,1-diphenyl-2-propyn-1-ol gave (PPh 3 ) 2 Cl 2 Ru(3-phenylinden-1-ylidene) (6). In situ exchange of PPh 3 with PCy 3 led to the isolation of 4 in > 90% yield. Whereas complex 6 did not show any activity in the cross metathesis reaction with styrene, reaction of compound 4 with excess styrene gave Grubbs× catalyst, (PCy 3 ) 2 Cl 2 Ru ¼ C(H)Ph (1), dichloro(phenylmethylene)bis-(tricyclohexylphosphane)ruthenium(II), in nearly quantitative yield. This two-step procedure yielded complex 1 in 88% overall yield starting from inexpensive and commercially available materials. The widely used metathesis catalyst 1 was also obtained in good yield in one single step, that is, without isolation of compound 4, making this a simple and safe synthetic route to Grubbs× catalyst.

Polyphenyl derivatives Q 0700Suzuki-Miyaura, α-Ketone Arylation and Dehalogenation Reactions Catalyzed by a Versatile N-Heterocyclic Carbene-Palladacycle Complex. -A detailed, extended account on previously published studies on the utilization of catalyst (I) in Suzuki-Miyaura coupling and α-ketone arylation reactions is presented. The catalyst is also highly efficient in dehalogenation reactions of aryl chlorides. -(NAVARRO, O.; MARION, N.; OONISHI, Y.; KELLY, R. A. I.; NOLAN*, S. P.; J. Org. Chem. 71 (2006) 2, 685-692; Dep. Chem., Univ. New Orleans, New Orleans, LA 70148, USA; Eng.) -Nuesgen 24-091