Synthesis and absolute stereochemistry of an organo-palladium complex containing a P-chiral diphosphine ligand

Abstract

The cationic palladium(II) complex containing ortho-metallated (R)-1-[1-(dimethylamino)ethyl]benzene and (1α, 4α, 5α(S), 7R)-[5-(diphenylphosphino)-2,3-dimethy-7-phenyl-7-phosphabicyclo[2.2.1]]-hept-2-ene was prepared by both the coordination of the diphosphine to the organopalladium unit and by the asymmetric Diels-Alder reaction between 1-phenyl-3,4-dimethylphosphole and diphenylvinylphosphine using the organopalladium unit as the reaction promoter. Compound C36H40CINO4P2Pd (-)-2, with [α]D -39.0 (c = 1.0, CHCl3), crystallizes in the monoclinic space group P21, with a = 10.538(4), b = 16.031(5), c = 10.709(4) Å, β = 100.20(3)°, V = 1781(1) Å3, Z = 2, Dc = 1.41 g cm-3, μ(Cu Kα) = 60.5 cm-1, F(000) = 776. The structure refinement converged to R1 = 0.033, wR2 = 0.081 for 2905 independent observed reflections [|F0| > 4σ(|F0|), 2θ ≤ 126°] and 387 parameters. The absolute stereochemistry of the phosphorus and the three carbon stereogenic centres in the diphosphine ligand were assigned unambiguously by both an R-factor test [R+ = 0.033, R- = 0.054] and the Flack parameter [x+ = -0.02(2), x- = +1.02(2)]. © 1997 Elsevier Science S.A.