Synthesis and reactivity of palladium and nickel β-diimine complexes:: Application as catalysts for Heck, Suzuki, and Hiyama coupling reactions

The synthesis of a range of sterically hindered beta-diimine ligands and their complexes with palladium(II) and nickel(II) of the formula Pd(kappa N-2,N-RN=CHC(CH2)(n)-CH=NR)(Cl-2) (R = 2,6-i-Pr2Ph, 2,6-Me2Ph, Cy, t-Bu, n = 4, 5) and Ni(kappa N-2,N-RN=CHC(CH2)(4)-CH=NR)(Br-2) (R = 2,6-i-Pr2Ph, 2,6-Me2Ph) has been investigated. Representative X-ray structures of both ligands and complexes have been determined. The use of the palladium complexes as catalysts for Suzuki coupling of aryl halides and arylboronic acids has been examined. In addition, it has been shown that the palladium complexes are also active in the Heck reaction of aryl bromides and methyl acrylate as well as in the Hiyama coupling of aryl halides and phenyltrimethoxysilane.