Synthetic and spectroscopic studies of some novel pyrrole complexes

Abstract

Substituted arene-derivatives of pyrrole containing two different aromatic sites within the same molecule and complexes with a metallocarbonyl group π-bonded to either or both of these sites have been prepared. The separate π-bonded tricarbonylmetal derivatives of 2-benzylpyrrole and 2-phenylpyrrole [Ar.C₄H₃NHₓM(CO)₃, Ar = C₆H₅CH₂-, C₆H₅; M = Mn(x=o), Cr (x = 1)] and the bimetallic derivative [C₆H₅CH₂.C₄H₃NCr(CO)₃Mn(CO)₃] have been isolated and characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance and mass spectrometry. The bimetallic derivative [C₆H₅.C₄H₃NCr(CO)₃Mn(CO)₃] has also been prepared but not fully characterized. All complexes are diamagnetic consistent with the Sidgwick 18-electron rule, the chromium and manganese atoms being π-bonded to the arene and pyrrolyl ring systems respectively. Spectroscopic studies were pursued to investigate electronic effects as a consequence of the formation of π-bonded metallocarbonyl derivatives of the 2-substituted pyrrole ligands. -- Novel pyrrole complexes of chromium(III) [(RC₄H₃N)₃Cr(III), R = -CHO; -COCH₃; -COC₆H₅] have also been prepared in which the 2-acylpyrrolato anion behaves as a bidentate chelating ligand. Characterization and structure assignments were made on the basis of elemental analyses, infrared and electronic spectral data and magnetic susceptibility measurements.