Inorganic Chemistry, Vol.48, No.23, 11114-11122, 2009
Multifaceted Coordination of Naphthyridine-Functionalized N-Heterocyclic Carbene: A Novel "Ir-III(C boolean AND N)(C boolean AND C)" Compound and Its Evaluation as Transfer Hydrogenation Catalyst
The 1,8-naphthyridine-functionalized N-heterocyclic carbene 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazol-2-yl-idene (BIN) has been successfully coordinated to Pd(II), W(0), Rh(l), and Ir(III), exhibiting its diverse binding modes. Reaction of BIN center dot HBr with Ag2O, followed by transmetalation with PdCl2(COD)(2) provides a cis complex PdCl2(kC(2)-BIN)(2) (1). Treatment of BIN center dot HBr with W(CO)(4)(pipeddine)(2) in acetonitrile affords a chelate complex W(CO)(4)(k(2)C(2),N-1'-BIN) (2). Reaction of {RhCl(COD)}(2) with KOBu and subsequent treatment with BIN center dot HBr in 1:2 and 1:1 ratio results in the mono and dinuclear complexes [Rh(COD)Br(KC2-BIN)] (3) and [{Rh(COD)Br)(2)(KN8':C-K(2)-BIN)] (4), respectively. In complex 3, the "Rh(COD)Br" unit is coordinated to the carbene center, whereas an additional "Rh(COD)Br" unit is attached to naphthyridine nitrogen in complex 4 in an anti arrangement. Under identical reaction condition, a novel Ir(III) complex [Ir((KC2)-C-2,N-1'-BIN)((KC3)-C-2',C-2-BIN)(H2O)Br]Br (5) has been synthesized. Complex 5 is proved to be catalytically active in hydrogen transfer reaction from PrOH. All complexes have been characterized by spectroscopic methods and X-ray crystallography.