STERIC EFFECTS ALONG LIGANDS IN BIS(TRIMETHYLSILYL) CYCLOPENTADIENYL COMPLEXES OF RUTHENIUM - ANALYSIS BY RADIAL PROFILES

The new complexes [(eta(5)-C5H3(SiMe(3))(2))Ru(CO)(L)I] (L = (t)BuNC, PMe(3), PPh(2)Et, PPh(3), P(OMe)(3), P((OPr)-Pr-i)(3), P(OPh)(3), and P(O-o-tol)(3) were prepared from the reaction between [(eta(5)-C5H3(Si Me(3))(2))Ru(CO)(2)I] and L in the presence of [(eta(5)-C5H3(SiMe(3))( 2))Ru(CO)(2)](2) as catalyst. Analysis of the complexes with L = PMe(3 ), PPh(3) and P(O-o-tol)(3) by the nOe technique revealed restricted r otation of the cyclopentadienyl ligand with the ligand rotation decrea sing with increasing size of L. No free rotation of the cyclopentadien yl ring in the analogous [(eta(5)-C5H3(SiMe(3))(2))Fe(CO)(L)I] complex es was observed. Regression analysis of NMR spectral parameters for th e various cyclopentadienyl ring protons, as well as solid angle radial profiles, cone angle radial profiles and solid angle of overlap (Gamm a) radial profiles identified that the differences between the rutheni um and iron complexes were related to the steric interaction between t he hydrogen atoms of the trimethylsilyl ring substituents and L.