Pt–M (M = Au and Tl) Dative Bonds Using Bis(cyclometalated)platinum(II) Complexes

Symmetrical and unsymmetrical biscyclometalated platinum­(II) complexes [Pt­(ptpy)2], 1, and [Pt­(ptpy)­(bppy)], 2, in which ptpy = deprotonated 2-(p-tolyl)­pyridine and bppy = deprotonated 2-(3-bromophenyl)­pyridine, have been prepared from the reaction between tris­(pentafluorophenyl)­borane, B­(C6F5)3 and 1 equiv of monocyclometalated complexes [PtMe­(ptpy)­(ptpyH)], B, and [PtMe­(ptpy)­(bppyH)], C, respectively. The solid-state structures of 1 and 2 have been determined by X-ray crystallography. The reaction of 1 with 1 equiv of TlPF6 or [Au­(PPh3)]­OTF resulted in the production of heteronuclear complexes [Pt­(ptpy)2Tl]­PF6, 3 and {Pt­(ptpy)2[Au­(PPh3)]}­OTF, 4, respectively. X-ray diffraction data showed that in solid state, complex 4 exists as a mixture of supported and unsupported PtII–AuI-bonded structures, whereas complex 3 consists of an infinite helical chain structure built up by unsupported Pt–Tl dative bonds. Absorption, emission, and NMR spectroscopy data showed that both Pt–Tl and Pt–Au bonds in 3 and 4 have dynamic behavior. The low-temperature 1H, 31P­{1H}, and exchange spectroscopy NMR of 4 revealed two dynamic behaviors involving the rupture of the Au–Cipso bond as well as the dissociation–association of the [Au­(PPh3)]+ and Pt­(ptpy)2 fragments. All complexes displayed bright emission in the solid state, and their absorption and emission properties have been investigated both experimentally and by time-dependent density functional theory calculations.