New coupling reactions for the construction of carbon-rich C-7 bridged di-ruthenium complexes

Abstract : This microreview summarizes our work on new reactions to obtain ruthenium(II) binuclear species with seven conjugated carbon atoms between the remote metals in very mild conditions via C-C bond formation. (i) The treatment of trans-[Cl(dppe)(2)Ru-CdropC-CdropC-SiMe3] with [Fe(C5H5)(2)]PF6 leads to an unprecedented metal-assisted [2+2] coupling reaction between C(gamma)dropC(delta) bonds to produce trans-[Cl(dppe)(2)Ru-CdropC-CdropCHC(CH2)double bondCdouble bondCdouble bondRu(dppe)(2)Cl]PF6 including a cyclobutenyl bridge. (ii) Addition of a cationic allenylidene trans-[ClRu(dppe)(2)(double bondCdouble bondCdouble bondC(CH2R1)R-2)]BF4 (R-1 = H, CH3; R-2 = CH3, Ph) on the C(gamma)dropC(delta) bond of the diyne trans-[Cl(dppe)(2)Ru-CdropC-CdropC-H] leads to ruthenium bimetallic complexes trans-[Cl(dppe)(2)Ru-CdropC-C(CH3)double bondC(R-1)-C(R-2)double bondCdouble bondCdouble bondRu(dppe)(2)Cl]BF4 containing a planar delocalized “W”-shaped C-7 bridge with tunable pendant groups. These complexes display attractive redox and optical properties with a highly delocalized charge over the conjugated carbon atoms. The crystal structures of trans-[Cl(dppe)(2)Rudouble bondCdouble bondCdouble bondC(CH3)-C(H)double bondC(CH3)-CdropC-Ru(dppe)(2)Cl]BF4 and of the annealated complex were solved. (C) 2003 Elsevier B.V. All rights reserved.