Synthesis of Cyclopalladated Derivatives of ( E )‐ N ‐Benzylidene‐2‐(2,6‐dichlorophenyl)ethanamine and Their Reactivity towards Monodentate and Symmetric Bidentate Lewis Bases

Treatment of the monoimine ( E )‐ N ‐benzylidene‐2‐(2,6‐dichlorophenyl)ethanamine ( 1 ) with a stoichiometric amount of Pd(OAc) 2 in acetic acid at 60 °C under nitrogen produced the corresponding acetato‐bridged endo five‐membered ortho ‐cyclopalladated dimer [Pd{C 6 H 4 CH=N(CH 2 ) 2 (2,6‐Cl 2 C 6 H 3 )}(μ‐OAc)] 2 ( 2 ), which was isolated in pure form in 80 % yield. Reaction of 2 with an excess of LiCl in acetone gave rise to the corresponding chlorido‐bridged cyclopalladated dimer [Pd{C 6 H 4 CH=N(CH 2 ) 2 (2,6‐Cl 2 C 6 H 3 )}(μ‐Cl)] 2 ( 3 ) in 88 % yield. Compounds 2 and 3 reacted with an excess of [D 5 ]pyridine or a stoichiometric amount of PPh 3 to give the mononuclear compounds trans ‐ N , L ‐[Pd{C 6 H 4 CH=N(CH 2 ) 2 (2,6‐Cl 2 C 6 H 3 )}(X)(L)] ( 4 : X = OAc, L = [D 5 ]py; 5 : X = Cl, L = [D 5 ]py; 6 : X = OAc, L = PPh 3 ; 7 : X = Cl, L = PPh 3 ). Compounds 4 and 5 were prepared in a CDCl 3 /[D 5 ]py solution and studied by 1 H and 13 C{ 1 H} NMR spectroscopy, but they were not isolated. Compound 3 was treated with different types of symmetric bidentate Lewis bases in a 1:1 molar ratio to give high yields of the dinuclear compounds trans ‐ N , L ‐[(Pd{C 6 H 4 CH=N(CH 2 ) 2 (2,6‐Cl 2 C 6 H 3 )}Cl) 2 {μ‐L 2 }] [ 8 : L 2 = Ph 2 PCH 2 CH 2 PPh 2 ; 9 : L 2 = trans ‐Ph 2 PCH=CHPPh 2 ; 10 : L 2 = 4,4′‐bipyridine; 11 : L 2 = NH 2 CH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 NH 2 ; 12 : L 2 = NH 2 CH 2 (CHOH)CH 2 NH 2 )] in which the symmetric bidentate Lewis base bridged two identical cyclopalladated units. Compounds 1 – 3 and 6 – 12 were fully characterized by elemental analysis, mass spectrometry, IR and 1 H and 13 C{ 1 H} NMR spectroscopy. In addition, the crystal structures of 2 , 8· 2CH 2 Cl 2 , 10· 4CHCl 3 and 11· 2CH 2 Cl 2 were determined by single‐crystal X‐ray diffraction analysis. Also reported is the theoretical study of the differences in the absolute Gibbs free energies in acetone or CHCl 3 solution between the cis ‐ and trans ‐ N , L stereoisomers of compounds [Pd(C‐N)(X)(L)] in which Pd(C‐N) is a model of an endo five‐membered ortho ‐cyclopalladated imine, X is OAc, Cl, Br or I and L is py, NH 3 or PH 3 .