A series of well-defined, air- and moisture-stable (NHC)Pd(allyl)Cl (NHC = N-heterocyclic carbene) complexes has been used in several catalytic reactions: Suzuki-Miyaura cross-coupling, catalytic dehalogenation of aryl halides, and aryl amination. The scope of the three processes using various substrates was examined. A general system involving the use of (IPr)Pd(allyl)Cl as catalyst and NaO(t)Bu as base has proven to be highly active for the Suzuki-Miyaura cross-coupling of activated and unactivated aryl chlorides and bromides, for the catalytic dehalogenation of aryl chlorides, and for the catalytic aryl amination of aryl triflates. All reactions proceed in short reaction times and at mild temperatures. The system has also proven to be compatible with the microwave-assisted Suzuki-Miyaura cross-coupling and catalytic dehalogenation processes, affording yields similar to those of the conventionally heated analogous reactions.

Two new dicarbonyl N-heterocyclic carbene nickel(0) complexes of the type (NHC) 2 Ni(CO) 2 (NHC ) ICy, [N,N′-bis(cyclohexylimidazol)-2-ylidene (2), IMes [N,N′-bis(2,4,6-trimethylphenyl)imidazol)-2-ylidene] (3)) have been prepared by a substitution reaction of (NHC)Ni(CO) 2 (NHC ) I t Bu [N,N′-bis(tertbutylimidazol)-2-ylidene], IAd [N,N′-bis(1-adamantylimidazol)-2-ylidene]) and 2 equivalents of ICy or IMes. Single-crystal X-ray analyses confirmed the monomeric 18-electron compositions of [(ICy) 2 Ni(CO) 2 ] (2) and [(IMes) 2 Ni(CO) 2 ] (3). The greater electron-donating properties of the NHC ligands compared to tertiary phosphines are also demonstrated through calorimetric studies and enabled the determination of average bond dissociation enthalpies for Ni-L (L ) NHC and tertiary phosphine).

Polyphenyl derivativesPolyphenyl derivatives Q 0700 Cross-Coupling and Dehalogenation Reactions Catalyzed by (N-Heterocyclic carbene)Pd(allyl)Cl Complexes. -Air-and moisture-stable complex (Ib) is found to be an efficient catalyst for the Suzuki-Miyaura cross-coupling of aryl chlorides and bromides, dehalogenation of aryl chlorides, and amination of aryl triflates. The reactions can also be performed under microwave irradiation. -(NAVARRO, O.; KAUR, H.; MAHJOOR, P.; NOLAN*, S. P.; J. Org. Chem. 69 (2004) 9, 3173-3180; Dep. Chem., Univ. New Orleans, New Orleans, LA 70148, USA; Eng.) -Jannicke 35-080