Easy oxidative addition of the carbon–halogen bond by dimethylplatinum(II) complexes containing a related series of diimine ligands: Synthesis, spectral characterization and crystal structure

Dimethylplatinum(II) complexes [PtMe2(NN)] {NN = 4,4′-Me2bpy (4,4′-dimethyl-2,2′-bipyridine); 5,5′-Me2bpy (5,5′-dimethyl-2,2′-bipyridine)} were reacted with alkyl halides (RX = EtI, EtBr) to yield the organoplatinum(IV) complexes [PtMe2RX(NN)]. On the basis of NMR data, the platinum(IV) product of each reaction contains almost exclusively the trans isomer but small traces of the cis isomers are also observed. On the other hand, the reaction of [PtMe2(NN)] {NN = bu2bpy (4,4′-di-tert-butyl-2,2′-bipyridine); 4,4′-Me2bpy; 5,5′-Me2bpy} with CH2Br2 gave a mixture of cis and trans-[PtMe2(CH2Br)Br(NN)] formed by the oxidative addition of one of the C–Br bonds. The formation of the cis isomer increases in the order of 5,5′-Me2bpy > bu2bpy > 4,4′-Me2bpy. The reaction of [PtMe2(NN)] {NN = bpy (2,2′-bipyridine), phen (1,10-phenanthroline)} with 1,8-dibromooctane or 1,9-dibromononane afforded the mononuclear complexes [PtMe2{(CH2)nBr}Br(NN)] (n = 8–9). The products were fully characterized by elemental analysis, 1H, 13C, HH COSY, HMQC, DEPT and DEPTQ-135 NMR spectroscopy. The crystal structure of [PtMe2EtI(4,4′-Me2bpy)] reveals that Pt(IV) atom is six-coordinated in a slightly distorted octahedral geometry with the ethyl group trans to iodide.