Novel platinum(II) compounds with N-benzylidenebenzylamines:: Synthesis, crystal structures and the effect of cis or trans geometry on cycloplatination

Coordination compounds with a trans-stereochemistry were prepared for ligands (4-ClC6H4)CH=NCH2(4'-ClC6H4) (L-a), (2,4,6-Me3C6H2)CH=NCH2(4'-ClC6H4) (L-b) and (2,6-Cl2C6H3)CH=NCH2(4'-ClC6H4) (L-c) and were shown to be precursors of the corresponding cyclometallated compounds. The reactions between cis-[PtCl2(dmso)(2)] and ligands ArCH=NCH2(4'-ClC6H4) (Ar = 2-BrC6H4 (L-d); 2-ClC6H4 (L-e); C6F5 (L-f); 2,6-F2C6H3 (L-g)) under previously described conditions for cycloplatination of N-benzylidenebenzylamines gave a cyclometallated compound only for imine L-f; the other imines produced coordination compounds with a cis arrangement from which cyclometallation could not be achieved. Formation of either cis or trans coordination compounds [PtCl2(L)dmso] (L = N-benzylidenebenzylamine) can be related to steric effects and to the E/Z configuration of the C=N bond. All compounds were fully characterized including structure determinations for trans-[PtCl2{(4-ClC6H4)CH=NCH2(4'-ClC6H4)}SOMe2] (2a), trans-[PtCl2[{2,6-Cl2C6H3)CH=NCH2(4'-ClC6H4)}SOMe2] (2c) and the amine derivative trans-[PtCl2(4-ClC6H4CH2NH2)SOMe2] (2) obtained as a by-product. (C) 2008 Elsevier Ltd. All rights reserved.