Cyclometallation of 2-phenylaniline and (R)-α-methylbenzylamine by palladium(II) acetate. X-ray molecular structure of [Pd{2-(2′-NH2C6H4)C6H4}Br(PPh3)]

Article abstract of DOI:10.1016/0022-328X(96)06188-8

The action of palladium(II) acetate on the primary amines 2-phenylaniline and (R)-α-methylbenzylamine and subsequent treatment with LiBr allows the preparation of the corresponding cyclopalladated dimers [Pd(C-N)Br]₂ (1a and 1b respectively). Mononuclear compounds [Pd(C-N)Br(L)], 3 (L = py-d₅) and 2 (L = PPh₃), have been obtained by reaction of 1 with py-d₅ and PPh₃. Addition of PPh₃ to chloroform solutions of 2 produces a rapid exchange between coordinated and free PPh₃. ³¹P{¹H} NMR at variable temperature suggests that this exchange proceeds for 2a through the fast equilibrium [Pd(C-N)Br(PPh₃)₂] ? [Pd(C-N)Br(PPh₃)] + PPh₃, while the usual mechanism in substitution reactions in d⁸ planar square complexes is involved in the case of 2b. The X-ray crystal structure of 2a has been determined. 2a crystallizes in the triclinic space group P1 with a = 12.182(3), b = 10.502(2), c = 9.998(2) A, α = 99.24(2), β = 94.69(2) and γ = 99.13(2)°.