Halogen photoreductive elimination from metal-metal bonded iridium(II)-gold(II) heterobimetallic complexes.
Halogen oxidation of [Ir(I)Au(I)(dcpm)(2)(CO)X](PF(6)) (dcpm = bis(dicyclohexylphosphino)methane, X = Cl, Br) and [Ir(I)Au(I)(dppm)(2)(CN(t)Bu)(2)](PF(6))(2) (dppm = bis(diphenylphosphino)methane) furnishes the heretofore unknown class of d(7)-d(9) compounds comprising an Ir(II)Au(II) heterobimetallic core. A direct metal-metal bond is evident from a 0.2 A contraction in the intermetallic distance, as determined by X-ray crystallography. The photophysical consequence of iridium-gold bond formation, as elucidated by experimental and computational investigations, is an electronic structure dominated by a sigma --> sigma* transition that possesses significant ligand-to-metal charge transfer (LMCT) character. Accordingly, these compounds are non-emissive but photoreactive. Excitation of Ir(II)Au(II) complexes in the presence of a halogen trap prompts a net photoreductive elimination of halogen and the production of the two-electron reduced Ir(I)Au(I) species with about 10% quantum efficiency. The Ir(II)Au(II) complexes add to a growing library of d(7)-d(9) heterobimetallic species from which halogen elimination may be driven by a photon.
Teets
Thomas S
TS
Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA.
Lutterman
Daniel A
DA
Nocera
Daniel G
DG
D018360:Crystallography, X-Ray; D006046:Gold / Q000737:chemistry*; D006219:Halogens / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008958:Models, Molecular; D010777:Photochemistry; D013057:Spectrum Analysis / Q000379:methods
D006219:Halogens; D007495:Iridium; D006046:Gold