A comparative study of metallating agents in the synthesis of [C,N,N′]-cycloplatinated compounds derived from biphenylimines

The reactions of ligands 4-C6H5C6H4CHNCH2CH2NMe2 (1a) and 2-C6H5C6H4CHNCH2CH2NMe2 (1b) in front of cis-[PtCl2(dmso)2] or cis-[PtPh2(SMe2)2] produced compounds [PtCl2{4-C6H5C6H4CHNCH2CH2NMe2}] (2aCl) and [PtCl2{2-C6H5C6H4CHNCH2CH2NMe2}] (2bCl) or [PtPh2{4-C6H5C6H4CHNCH2CH2NMe2}] (2aPh) and [PtPh2{2-C6H5C6H4CHNCH2CH2NMe2}] (2bPh). From all these compounds, the corresponding cyclometallated [C,N,N′] platinum(II) compounds 3aCl, 3bCl, 3aPh and 3bPh were obtained although under milder conditions and with higher yields for the phenyl derivatives. The reaction of compounds 3aPh and 3bPh with methyl iodide gave cyclometallated [C,N,N′] platinum(IV) compounds 4aPh and 4bPh of formula [PtMePhI{C6H5C6H3CHNCH2CH2NMe2}]. Compounds 3aCl and 3bCl containing a chloro ligand, although unreactive towards methyl iodide, undergo oxidative addition of chlorine to produce the corresponding platinum(IV) compounds [PtCl3{4-C6H5C6H3CHNCH2CH2NMe2}] (6aCl and 6bCl). All compounds were characterised by NMR spectroscopy and crystal structures of compounds 3bCl and 6bCl are also reported.