Syntheses of chromium tricarbonyl organometals of 1-methyl-naphthalene and different polycyclic aromatic hydrocarbons, characterisation of the (C11H10)Cr(CO)3 isomers and the crystal structure of the [(η6-5,6,7,8,9,10-C11H10)Cr(CO)3] complex

The synthesis of organometal complexes from chromium hexacarbonyl with 1-methyl-naphthalene ligand is reported. Two arene-chromium-tricarbonyl isomers are formed at competitive yields, featured with the metal fragment coordinated to both the methylated and the benzenic aromatic ring. A single-crystal X-ray diffraction measurement has been performed on the [(η6-5,6,7,8,9,10-C11H10)Cr(CO)3] isomer, which presents the metal carbonyl moiety attached to the benzenic arene ligand. The products of reaction have been studied by UV–VIS–NIR, fluorescence and 1H NMR spectroscopies. A detailed vibrational characterisation by mean of experimental FT-IR and Raman spectroscopy and DFT calculations is reported. The electron ligand donation to the metal carbonyl system, determined by FT-IR spectroscopy, has been related to the actual decrease of resonance energy of the aromatic hydrocarbon in the complex and compared with other chromium tricarbonyl complexes of different polycyclic aromatic hydrocarbons provided with the naphthalenic moiety.

Graphical abstractThe structural study of 1-methyl-naphthalene chromium tricarbonyl combined with a vibrational and quantum chemical analysis of differing PAH permits an interpretation of metal-PAH bond in term of ligand aromaticity’s perturbation. Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and characterisation of arene Cr(CO)3 complexes. ► Structure of a regioisomer of CH3-naphthalene compound. ► A simple model of ligand covalent resonance structures is proposed to classify the ligand donor ability