Reaction of (η2-arylaldehyde)nickel(0) complexes with Me3SiX (X=OTf, Cl). Application to catalytic reductive homocoupling reaction of arylaldehyde

Arylaldehydes can coordinate to nickel(0) in η2-fashion to give η2-arylaldehydenickel complexes, which react with Me3SiOTf or Me3SiCl to give η1:η1-siloxybenzylnickel or η3-siloxybenzyl complex. In the presence of PCy3 or CO, η1:η1-siloxybenzylnickel complex underwent homocoupling reaction to give a pinacol type product. In the presence of zinc dust, the reductive homocoupling reaction of arylaldehyde proceeded catalytically to form pinacol derivatives in 70-99% yield. On the other hand, η3-siloxybenzylnickel complex regenerated benzaldehyde and Me3SiOTf under a carbon monoxide pressure.

Arylaldehydes reacts with nickel(0) and Me3SiCl to give η1:η1-siloxybenzylnickel complex. In the presence of zinc dust, the reductive homocoupling reaction of arylaldehyde proceeded catalytically to form pinacol derivatives.