Propene complexes of molybdenum and tungsten stabilized by intramolecular coordination of the 1-(quinol-8-yl)indenyl ligand

Abstract

We report herein a new class of mixed propene-indenyl complexes of molybdenum and tungsten stabilized by a strong N→M intramolecular coordination. The complexes [{η⁵:κN-1-(C₉H₆N)C₉H₆}(η²-C₃H₆)M(CO)₂][BF₄] (M = Mo, W) were obtained in nearly quantitative yields by the protonation of the η³-allyl ligand in compounds [(η³-C₃H₅){η⁵-1-(C₉H₆N)C₉H₆}M(CO)₂] (M = Mo, W). In contrast to known η²-alkene molybdenum and tungsten compounds, the species presented here are easily isolated in the solid state. The tungsten compound [{η⁵:κN-1-(C₉H₆N)C₉H₆}(η²-C₃H₆)W(CO)₂][BF₄] is stable at room temperature, and its structure was unambiguously confirmed by X-ray diffraction. The reactivity of both propene complexes toward several monodentate donors was examined. In the case of dimethyl sulfide, ligand exchange takes place to afford [{η⁵:κN-1-(C₉H₆N)C₉H₆}M(CO)₂(SMe₂)][BF₄] (M = Mo, W) while acetonitrile induces η⁵ → η³ haptotropic rearrangement to give [{η³:κN-1-(C₉H₆N)C₉H₆}M(CO)₂(NCMe)₂][BF₄] (M = Mo, W).