Studies on the enantioselective addition of enol silyl ethers to imines catalyzed by optically active palladium diaquo complexes 3 or binuclear palladium mu-hydroxo complex 4 are described, with particular focus on the mechanistic aspects. Asymmetric induction in the reaction using [Pd((R)-binap)(H2O)(2)](2+)(BF4-)(2) (3a) was quite sensitive to the reaction conditions, suggesting unfavorable effects of HBF4 generated from 3a in situ. Novel optically active binuclear mu-hydroxo complexes [{Pd((R)-binap)Cu-OH)}(2)](2+)(BF4-)(2) (4a), [{Pd((R)-tol-binap)(mu-OH)}(2)](2+)(BF4-)(2) (4b), [{Pd((R)-binap)Cu-OH)}(2)](2+)(TfO-)(2) (4c), and [{Pd((R)-tol-binap)(mu-OH)}(2)](2+)(TfO-)(2) (4d) were prepared and were found to be better catalysts for the asymmetric Mannich-type reaction. Benzoylalanine derivatives 5 were obtained in excellent chemical and optical yields (up to 90% eel. Mechanistic studies using H-1 NMR and electrospray ionization mass spectrometry indicated that a unique binuclear palladium-sandwiched enolate 12 was involved in the reaction of enol silyl ether 1 with imine 2 catalyzed by 4.