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A detailed study on modifications in the ligand sphere of molybdenum alkylidynes with tripodal ligand frameworks is presented. The project was based on the “canopy catalysts” recently introduced by HILLENBRAND et al. and intended to further explore different aspects of the design.[1-3]
Well-defined molybdenum alkylidynes were prepared through protolysis of precursor complexes of type [Mo(≡CAr)(OtBu)3] with various tripodal ligands (Scheme 1). These complexes were evaluated with respect to their catalytic activity in alkyne metathesis and their stability towards water.
A catalyst endowed with a n-butyl substituted silanolate ligand was found to exhibit a moderate tolerance towards water and air, while retaining excellent catalytic activity. Varying the aryl alkylidyne unit revealed its electronic influence to be negligible with regard to the catalytic performance. However, the 2,6-di(methyl) benzylidyne unit was found to increase the stability significantly. The first molybdenum alkylidyne complex with a tripodal carbinolate ligand is presented. Additionally, a new tripodal scaffold for potential future catalyst design is introduced and its viability proven by the preparation of a prototype complex of excellent catalytic activity.
