title: Mono- and dinuclear palladium(II) N,S-heterocyclic carbene complexes with N spacers and their Suzuki coupling activities.
abstract: Mixed-ligand N,S-heterocyclic carbene (NSHC) complexes, trans-[PdBr(2)(NSHC)(Py)] (NSHC=3-benzyl- or 3-propyl-benzothiazolin-2-ylidene), have been obtained from bridge-cleavage reactions of the dinuclear complex, [Pd(mu-Br)Br(NSHC)](2), in pyridine at room temperature. Use of neutral N-bidentate donors (L=pyrazine, 1,2-bis(4-pyridyl)ethane, 4,4'-bipyridine and trans-1,2-bis(4-pyridyl)ethylene) yields the dinuclear spacer-bridged [Pd(2)Br(4)(NSHC)(2)(mu-L)] complexes. The X-ray single-crystal structures of the pyridyl, bridging pyrazine and 1,2-bis(4-pyridyl)ethane complexes are reported. These air-stable complexes are active in the Suzuki-Miyaura coupling reactions of selected aryl bromides. The dinuclear complexes are generally more active than their mononuclear pyridyl analogues. The benzyl derivatives consistently outperform the n-propyl counterparts.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Swee Kuan
authors.initials: SK
authors.lastname: Yen
authors.forename: Lip Lin
authors.initials: LL
authors.lastname: Koh
authors.forename: Han Vinh
authors.initials: HV
authors.lastname: Huynh
authors.forename: T S Andy
authors.initials: TS
authors.lastname: Hor