Platinum(II), palladium(II) and gold(III) adducts and cyclometalated derivatives of 6-methoxy-2,2′-bipyridine: A comparative study

•Rollover cyclometalation.•CH bond activation.•Bipyridine complexes.•Pt(II), Pd(II) and Au(III) cyclometalated complexes.

Reaction of 6-methoxy-2,2′-bipyridine (bpy6OMe) with the electron-rich platinum(II) complex [Pt(Me)2(DMSO)2] gave the rollover cyclometalated complex [Pt(κ2-N,C-bpy6OMe-H) (Me) (DMSO)] under mild conditions. The occurrence of rollover cyclometalation was demonstrated by single crystal X-ray diffraction structure determination. In contrast, reaction of bpy6OMe with [Pt(Ph)2(DMSO)2] and [Pt(Cl)2(DMSO)2] under mild conditions gave only adduct species of the type [Pt(X)2(bpy6OMe)] (X = Ph, Cl). Under harsher conditions, activation of a CH bond in the methoxy substituent yielded the terdentate cyclometalated complex [Pt (κ3-N,N,C-bpy6OMe-H)Cl]. Finally, reaction of Pd(II) and Au(III) derivatives invariably gave adduct species, with the exception of the dimeric complex [Pd(κ2-N,C-bpy6OMe-H) (OAc)]2, which, however, was not isolated in pure form. The reactivity of bpy6OMe, as emerged from this study, was compared with that of the corresponding disubstituted ligand 6,6′-dimethoxy-2,2′-bipyridine, previously studied by us.

Graphical abstractReaction of 6-methoxy-2,2′-bipyridine (bpy6OMe) with the electron-rich complex [Pt(Me)2(DMSO)2] gave the rollover cyclometalated complex [Pt(bpy6OMe-H) (Me) (DMSO)] under mild conditions. In contrast, electron poor Pt(II) complexes gave adduct species or terdentate N,N,C complexes. Finally, Pd(II) and Au(III) derivatives gave adduct species in most of the conditions studied.Figure optionsDownload full-size imageDownload as PowerPoint slide