Synthesis and reactivity towards carbon monoxide of an optically active endo five-membered ortho-cyclopalladated imine: X-ray molecular structure of trans-(μ-Cl) 2[Pd(κ 2- C, N-( R)-C 6H 4-CH [dbnd]N-CHMe-Ph)] 2

Abstract

( R)-1-Phenylethyl-benzylidene-amine ( 1) reacted with Pd(OAc) 2 in acetic acid at 60 °C under nitrogen affording the acetato-bridged dinuclear endo five-membered ortho-cyclopalladated compound (μ-OAc) 2[Pd(κ 2- C, N-( R)-C 6H 4-CH N-CHMe-Ph)] 2 ( 2) in 65% yield. Compound 2 was converted by a metathesis reaction with LiCl into the corresponding chloro-bridged dinuclear cyclopalladated compound (μ-Cl) 2[Pd(κ 2- C, N-( R)-C 6H 4-CH N-CHMe-Ph)] 2 ( 3). 1H NMR of CDCl 3 solutions of compounds 2 and 3 treated separately with py- d 5, ( R)-1-phenylethylamine and racemic 1-phenylethylamine were consistent with the endo cyclopalladated structure and the R absolute configuration of the chiral carbon atoms of compounds 2 and 3. Compounds 2 and 3 reacted with carbon monoxide in methanol affording, as major compounds, methyl 2-formylbenzoate (91% chemical yield) and the epimers of 3-methoxy-2-[( R)-1-phenylethyl]isoindolin-1-one (64% chemical yield) in ca. 20% diastereomeric excess, respectively. The trans isomer of compound 3 crystallized in the P2 1 monoclinic space group with a = 10.430(4) Å, b = 12.082(8) Å, c = 11.168(4) Å and β = 95.20(3)° and presented C–H⋯Cl intramolecular and C–H⋯Pd intermolecular non-conventional hydrogen bonds.