Cyclometallated derivatives of platinum( II ) derived from 6-(tert-butyl)-2,2′-bipyridine (HL). Crystal and molecular structure of [Pt(L)CI]

The reaction of K2[PtCI4] with 6-(tert-butyl)-2,2′-bipyridine (HL) gave [Pt(L)CI]1a a cyclometallated species resulting from direct activation of a methyl C–H bond. The structure has been determined by X-ray diffraction. The crystals contain two independent molecules: average values for the principal parameters are Pt–CI 2.300, Pt–C 2.003, Pt–N (trans to C) 2.114 and Pt–N (trans to CI) 1.948 Å. The chlorine atom in 1a can easily be displaced by neutral ligands (L′); in the presence of NaBF4 the cationic species [Pt(L)(L′)][BF4](L′= PPh32, CO 3 or 3,5-dimethylpyridine 4) were isolated in good yields. With potentially bidentate neutral ligands, L″–L″[Ph2P(CH2)2PPh2(dppe), Ph2P(CH2)2AsPh2(dadpe) or Ph2PCCPPh2(dppa)], [LPt(µ–L″–L″)PtL]2+(L″–L″= dppe 5, dadpe 6 or dppa 7) or [PtL(L″–L″)]+ species (L″–L″= dppe 8 or dadpe 9) can be obtained by adequate choice of the L″–L″ : Pt molar ratio (1 : 2 or 1 : 1, respectively). The new complexes 1–9 were characterized in solution by 1H, 13C-{1H} NMR spectra.