Alkaline Earth Metal Compounds of Methylpyridinato β‑Diketiminate Ligands and Their Catalytic Application in Hydroboration of Aldehydes and Ketones

Ever increasing demand
for green and sustainable chemical processes
has set up a drive to replace transition metals with earth-abundant,
nontoxic, and environmentally benign alternatives. In this regard,
the alkaline earth metal complexes have attracted significant attention.
Herein, we have used a β-diketiminato ligand with methyl-pyridine
side arm to synthesize magnesium (1) and calcium (2) compounds. The constitutions of 1 and 2 have been confirmed by single crystal X-ray studies, which
show that the magnesium and calcium atom in 1 and 2 possesses octahedral geometry. Subsequently, we have used
them as catalysts (1 mol %) for hydroboration of a wide range of aldehydes
using pinacolborane (HBpin) at room temperature. The strategy has
further been extended to ketones with 2 mol % catalyst loading. DFT
calculations have been performed to understand the mechanism.