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

Abstract

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.