Low Coordinate
Germanium(II) and Tin(II) Hydride Complexes:
Efficient Catalysts for the Hydroboration of Carbonyl Compounds
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Abstract
This study details the first use
of well-defined low-valent p-block
metal hydrides as catalysts in organic synthesis. That is, the bulky,
two-coordinate germanium(II) and tin(II) hydride complexes, L<sup>†</sup>(H)M: (M = Ge or Sn, L<sup>†</sup> = −N(Ar<sup>†</sup>)(SiPr<sup>i</sup><sub>3</sub>), Ar<sup>†</sup> = C<sub>6</sub>H<sub>2</sub>{C(H)Ph<sub>2</sub>}<sub>2</sub>Pr<sup><i>i</i></sup>-2,6,4), are shown to act as efficient catalysts
for the hydroboration (with HBpin, pin = pinacolato) of a variety
of unactivated, and sometimes very bulky, carbonyl compounds. Catalyst
loadings as low as 0.05 mol % are required to achieve quantitative
conversions, with turnover frequencies in excess of 13 300
h<sup>–1</sup> in some cases. This activity rivals that of
currently available catalysts used for such reactions
