3-(η⁶-Benzoyltricarbonylchromium)pyrrole. An example of how substitution isomerism in the ligand affects the type (σ or π) of complex formed

Abstract

The reaction of 3-benzoylpyrrole and Cr(CO)6 yields only the π-complex 3-(η6-benzoyltricarbonylchromium)pyrrole, in contrast to the previously reported reaction of 2-benzoylpyrrole and Cr(CO)6 that yielded only the σ-chelate, tris(2-benzoyl-pyrrolato)chromium(III). The difference in behaviour is explained by a preference for chelate formation that is allowed by the stereochemistry of 2-benzoylpyrrole but is not allowed by the stereochemistry of 3-benzoylpyrrole.

Synthesis and spectroscopic studies of some substituted 3-benzoylpyrroles and their tricarbonylchromium complexes

“…3-Benzoylpyrrole was prepared as described previously (8 For personal use only. bonylchromium complexes were prepared from the parent pyrrole and Cr(C0)6 in refluxing di-n-butyl ether as previously described (9). The N-methyl derivatives of the ligands and complexes were prepared by reaction with dimethyl sulfate using phase transfer catalysis as outlined previously (10).…”