Substitution reactions of(C(5)Ph(5))Cr(CO)(3): Structural, electrochemical, and spectroscopic characterization of (C(5)Ph(5))Cr(CO)(2)L (L=PMe(3), PMe(2)Ph, P(OMe)(3))

The radical complex (C(5)Ph(5))Cr(CO)(3) reacts with small, neutral, monodentate Lewis bases (PMe(3), PMe(2)Ph, P(OMe)(3)) in THF at -78 degrees C (PMe(2)Ph reacts at ambient temperature) to yield the monomeric substitution products (C(5)Ph(5))Cr(CO)(2)L . THF as thermally stable solids. Electrochemical and spectroscopic data are provided. An X-ray crystal structure of the hemisolvate (C(5)Ph(5))Cr(CO)(2)PMe(3) . 0.5THF was obtained. Frozen-solution ESR spectra of (C(5)Ph(5))Cr(CO)(2)L in toluene are comparable to those of other low-spin d(5) ''piano-stool'' complexes. Rotation of the Cr(CO)(2)L moiety relative to the C(5)Ph(5) ring is rapid on the ESR time scale in low-temperature liquid solutions and leads to axial powderlike spectra. Analysis of this effect leads to significant insights into the electronic structure.