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(C ₆ F ₅ ) 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 TlPF ₆ or [Au(PPh ₃ )]OTF resulted in the production of heteronuclear complexes [Pt(ptpy) ₂ Tl]PF ₆ , 3 and {Pt(ptpy) ₂ [Au(PPh ₃ )]}OTF, 4, respectively. X-ray diffraction data showed that in solid state, complex 4 exists as a mixture of supported and unsupported Pt ^II -Au ^I -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 ¹ H, ³¹ P{ ¹ H}, and exchange spectroscopy NMR of 4 revealed two dynamic behaviors involving the rupture of the Au-C _ipso bond as well as the dissociation-association of the [Au(PPh ₃ )] ⁺ 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.