1 research outputs found
Preparation and Hydrosilylation Activity of a Molybdenum Carbonyl Complex That Features a Pentadentate Bis(imino)pyridine Ligand
Attempts to prepare low-valent molybdenum
complexes that feature a pentadentate 2,6-bisÂ(imino)Âpyridine (or pyridine
diimine, PDI) chelate allowed for the isolation of two different products.
Refluxing MoÂ(CO)<sub>6</sub> with the pyridine-substituted PDI ligand, <sup>PyEt</sup>PDI, resulted in carbonyl ligand substitution and formation
of the respective bisÂ(ligand) compound (<sup>PyEt</sup>PDI)<sub>2</sub>Mo (<b>1</b>). This complex was investigated by single-crystal
X-ray diffraction, and density functional theory calculations indicated
that <b>1</b> possesses a Mo(0) center that back-bonds into
the π*-orbitals of the unreduced PDI ligands. Heating an equimolar
solution of MoÂ(CO)<sub>6</sub> and the phosphine-substituted PDI ligand, <sup>Ph2PPr</sup>PDI, to 120 °C allowed for the preparation of (<sup>Ph2PPr</sup>PDI)ÂMoÂ(CO) (<b>2</b>), which is supported by a
κ<sup>5</sup>-<i>N</i>,<i>N</i>,<i>N</i>,<i>P</i>,<i>P</i>-<sup>Ph2PPr</sup>PDI chelate. Notably, <b>1</b> and <b>2</b> have been
found to catalyze the hydrosilylation of benzaldehyde at 90 °C,
and the optimization of <b>2</b>-catalyzed aldehyde hydrosilylation
at this temperature afforded turnover frequencies of up to 330 h<sup>–1</sup>. Considering additional experimental observations,
the potential mechanism of <b>2</b>-mediated carbonyl hydrosilylation
is discussed