Substituted cyclopentadienyl ligands .11. Steric interactions in mono(trimethylsilyl)cyclopentadienyl complexes of molybdenum

Reaction of C(5)H(4)SiMe(3) with Mo(CO3) yields [(eta(5)-C(5)H(4)SiMe(3))Mo(CO3)(2)], which upon cleavage with iodine gives [(eta(5)-C(5)H(4)SiMe(3))Mo(CO)(3)I]. Carbonyl displacement by a range of ligands, L (L = (1)BuNC, PMe(3), P(OMe)(3), PMe(2)Ph, P((OPr)-Pr-i)(3), PPh(2)Me, P(O-o-tol)(3), PPh(3), and P(m-tol)(3)) gives the new complexes [(eta(5)-C(5)H(4)SiMe(3))Mo(CO)(2)(L)I]. H-1 NMR and LR spectral analysis revealed that the complexes existed as a mixture of cis and trans isomers but the equilibrium ratio of isomers was not linearly related to either steric or electronic factors associated with the molecule. H-1 NMR analysis of the ring proton resonance positions of the new complexes revealed that the steric effect of the trimethylsilyl ring substituent (theta or Omega(3)) was similar to that of the tertiary-butyl group.