Assembly of Cyclometalated Platinum(II) Complexes via 1,1 '-Bis(diphenylphosphino)ferrocene Ligand: Kinetics and Mechanisms

作者：Nabavizadeh S Masoud^*; Amini Hashem; Shahsavari Hamid R; Namdar Masoud; Rashidi Mehdi; Kia Reza; Hemmateenejad Bahram; Nekoeinia Mohsen; Ariafard Alireza; Hosseini Fatemeh Niroomand; Gharavi Alireza; Khalafi Nezhad Ali; Sharbati Mohammad Taghi; Panahi Farhad

来源：Organometallics, 2011, 30(6): 1466-1477.

DOI：10.1021/om101055n

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 P-31 NMR spectroscopies. When 0.5 equiv of dppf was added, the binuclear Pt(II) complex [Pt2Ar2(C-N)(2)(mu-dppf)], 2, was formed in a good yield. The complexes were fully characterized using multinuclear (H-1, P-31, and Pt-195) NMR spectroscopy, and the structure of complex [Pt-2(p-MeOC6H4)(2)(bhq)2(mu-dppf)], 2c'center dot CH2Cl2, was further identified by X-ray crystallography. On the basis of low-temperature P-31 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-kappa P-1)], A, in which dppf-kappa P-1 is a monodentate dppf ligand, which rapidly forms an equilibrium with the chelating dppf isomer complex [Pt(p-MeC6H4)(dppf)(ppy-kappa C-1)], B, in which ppy-kappa C-1 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 [Pt-2(p-MeC6H4)(2)(ppy)(2)(mu-dppf)], 2b. A competitive-consecutive second-order reaction mechanism was suggested for the reaction using chemometric studies, and the rate constants at 5 degrees C for first and second steps were estimated as k(2) = 10.7 +/- 0.2 L mol(-1)s(-1) and k(2)' = 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 degrees C being k(2) = 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 P-31 and Pt-195 NMR spectra, was proposed to be [(p-MeC6H4)(Ppy)Pt-(mu-dppf)Pt(p-MeC6H4)(ppy-kappa C-1)(dppf-kappa P-1)]; the same results were obtained when more than 1, e.g., 2, equiv of dppf was used, with a similar rate constant of k(2) = 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.

• 出版日期2011-3-28