Synthesis and characterization of planar-chiral cyclopentadienylruthenium-vinylidene complexes

Enantiopure planar-chiral cyclopentadienylruthenium-vinylidene complexes, ( S-Cl)- and (R-Cl)-[(eta (5)-C5H2-1 -COR'-2-Me-4-R-2)RU(PPh3)(2)(=C=CHR3)1[P F6] (4: R-1 = O-(l)- and O-(d)-menthyl; 8: R-1 = NH'Bu. R-2 = Me, Ph; R-3 = Ph, H), were synthesized starting from [(eta (5)-C5H2-1-COR1 -2-Me-4-R-2)R u(eta (6)-C6H6)][PF6], and characterized by optical and spectra methods inc luding H-1, C-13,and P-31-NMR, and CD spectra. The reaction rate of [(eta ( 5)-C5H2-1-CO2Et-2,4-Me,)Ru(PPh3)(2)(MeCN)(3)[PF6] with phenylacetylenes lea ding to vinylidene complexes increases in the order: HCCC6H4NO2 < HCCC6H5 < HCCC6H5OMe. Analysis by cyclic voltammetry showed that trisubstituted cycl opentadienyl ligands C5H2-1-CO2Et-2-Me-4-R-2 (R-2 = Me, Ph, 'Bu, Naph etc.) act as a weak electron-donor compared with non-substituted cyclopentadieny l one in ruthenium-phenylacetylide complexes. (C) 2001 Elsevier Science B.V . All rights reserved.