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

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 [{η:κN-1-(CHN)CH}(η-CH)M(CO)][BF] (M = Mo, W) were obtained in nearly quantitative yields by the protonation of the η-allyl ligand in compounds [(η-CH){η-1-(CHN)CH}M(CO)] (M = Mo, W). In contrast to known η-alkene molybdenum and tungsten compounds, the species presented here are easily isolated in the solid state. The tungsten compound [{η:κN-1-(CHN)CH}(η-CH)W(CO)][BF] 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 [{η:κN-1-(CHN)CH}M(CO)(SMe)][BF] (M = Mo, W) while acetonitrile induces η→η haptotropic rearrangement to give [{η:κN-1-(CHN)CH}M(CO)(NCMe)][BF] (M = Mo, W).