Supporting Information
Assembly of Cyclometalated Platinum(II) Complexes via 1,1′-Bis(diphenylphosphino)ferrocene Ligand: Kinetics and Mechanisms
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Crystallographic Information File
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The kinetics and mechanism of the reaction of the cyclometalated complexes [PtAr(C−N)(SMe2)], 1, in which Ar is Ph, p-MeC6H4, or p-MeOC6H4, and C−N is either ppy (deprotonated 2-phenylpyridine) or bhq (deprotonated benzo[h]quinoline), with 1,1′-bis(diphenylphosphino)ferrocene, dppf, were studied using UV−visible and 31P NMR spectroscopies. When 0.5 equiv of dppf was added, the binuclear Pt(II) complex [Pt2Ar2(C−N)2(μ-dppf)], 2, was formed in a good yield. The complexes were fully characterized using multinuclear (1H, 31P, and 195Pt) NMR spectroscopy, and the structure of complex [Pt2(p-MeOC6H4)2(bhq)2(μ-dppf)], 2c′·CH2Cl2, was further identified by X-ray crystallography. On the basis of low-temperature 31P NMR studies involving the starting complex [Pt(p-MeC6H4)(ppy)(SMe2)], 1b, we suggest that dppf displaces the labile ligand SMe2 to give an uncommon complex, [Pt(p-MeC6H4)(ppy)(dppf-κ1P)], A, in which dppf-κ1P is a monodentate dppf ligand, which rapidly forms an equilibrium with the chelating dppf isomer complex [Pt(p-MeC6H4)(dppf)(ppy-κ1C)], B, in which ppy-κ1C is the deprotonated ppy ligand that is C-ligated with the dangling N atom. In the second step, A is reacted with the remaining second half of starting complex 1b to give the final Pt(II)−Pt(II) binuclear complex [Pt2(p-MeC6H4)2(ppy)2(μ-dppf)], 2b. A competitive-consecutive second-order reaction mechanism was suggested for the reaction using chemometric studies, and the rate constants at 5 °C for first and second steps were estimated as k2 = 10.7 ± 0.2 L mol−1 s−1 and k2′ = 0.68 ± 0.05 L mol−1 s−1, respectively. When the starting complex [Pt(p-MeC6H4)(ppy)(SMe2)], 1b, was reacted with 1 equiv of dppf, similarly the complex A, in equilibrium with B, was formed first, with the rate constant at 5 °C being k2 = 10.5 ± 0.5 L mol−1 s−1, estimated using UV−visible spectroscopy. Subsequently, however, A and B would slowly and reversibly react with each other to form a new species, C, the structure of which, on the basis of 31P and 195Pt NMR spectra, was proposed to be [(p-MeC6H4)(ppy)Pt(μ-dppf)Pt(p-MeC6H4)(ppy-κ1C)(dppf-κ1P)]; the same results were obtained when more than 1, e.g., 2, equiv of dppf was used, with a similar rate constant of k2 = 10.6 ± 0.6 L mol−1 s−1. The complexes 1b and 2b were shown to have some interesting photophysical properties as investigated by absorption and electroluminescence spectroscopies.
Crystallographic data in CIF format and details of the chemometric method used for the kinetic study. These materials are available free of charge via the Internet at http://pubs.acs.org.