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 η 2 -fashion to give η 2 -arylaldehydenickel complexes, which react with Me 3 SiOTf or Me 3 SiCl to give η 1 :η 1 -siloxybenzylnickel or η 3 -siloxybenzyl complex. In the presence of PCy 3 or CO, η 1 :η 1 -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, η 3 -siloxybenzylnickel complex regenerated benzaldehyde and Me 3 SiOTf under a carbon monoxide pressure.