Orthometallated primary amines. Part 1. Facile preparation of the first optically active cyclopalladated primary amines

Abstract

Reaction of [PdCl₂{NH₂CH(Me)Ph}₂]1 with AgCIO₄(1 : 2) gave a solution containing an orthopalladated complex 2. Addition to this solution of neutral ligands or NaBr led to isolation of the complexes [Pd{C₆H₄[CH(Me)NH₂-2]}(L₂)]CIO₄[L = pyridine 3a, L₂= cycloocta-1,5-diene(cod)3b or 2,2′-bipyridine 3c] or [{Pd{C₆H₄[CH(Me)NH₂-2]}(µ-Br)}₂]4, respectively. Reaction of 4 with PPh₃ or Tl(acac)(Hacac = acetylacetone) gave [Pd{C₆H₄[CH(Me)NH₂-2]}Br(PPh₃)]5 or [Pd{C₆H₄[CH(Me)NH₂-2]}(acac)]6, respectively. Complexes 1, 4 and 5 can be obtained optically pure by using (R)-(+)- or (S)-(–)-α-methylbenzylamine as starting material. The solid-state crystal structures of 3b and R-5 were determined at low temperatures. In both complexes the palladium atom adopts the usual square-planar co-ordination. The major angular distortion is associated with the small bite of the chelating ligand (80.8 and 81.2°, respectively). The weaker trans influence of the cod ligand in 3b accounts for ca. 0.02 Å longer Pd–N and Pd–C bonds in R-5 than in 3b. Short contacts between the perchlorate anion or bromo ligand in 3b or R-5 with the amino group (N ⋯ O 3.06 or N ⋯ Br 3.41 Å, respectively) probably represent hydrogen bonds.