Oxidative Addition of Halogens to Homoleptic Perfluoromethyl or Perfluorophenyl Derivatives of ACHTUNGTRENUNGPlatinum(II): A Comparative Study

摘要

The equilibrium geometries of the homoleptic perfluorinated organoplatinate( II) anions [PtACHTUNGTRENUNG(CF3)4]2 and [PtACHTUNGTRENUNG(C6F5)4]2 have been computed at the B3P86/LANL2DZ level of theory. Remarkably good agreement with the experimentally determined structures has been obtained by X-ray diffraction methods. The reactivity of [NBu4]2[Pt- ACHTUNGTRENUNG(CF3)4] (1) towards halogens (Cl2, Br2 , and I2) has been investigated by using a combined experimental and theoretical approach. The perfluoromethyl derivative 1 has been found to undergo clean oxidative addition of the three halogens under investigation, giving rise to [NBu4]2ACHTUNGTRENUNG[trans-PtACHTUNGTRENUNG(CF3)4X2] (X=Cl (7), Br (10), I (13)) in a quantitative and stereoselective way. In the lowtemperature reaction of the perfluorophenyl derivative [NBu4]2[PtACHTUNGTRENUNG(C6F5)4] (3) with Cl2 or Br2, the corresponding oxidative-addition products [NBu4]2- ACHTUNGTRENUNG[trans-PtACHTUNGTRENUNG(C6F5)4X2] (X= Cl (14), Br (15)) can also be obtained. In the case in which X=Br and working in CHCl3 at 55 8C, it has been possible to detect the formation of an intermediate species to which we assign the formula [trans-PtACHTUNGTRENUNG(C6F5)4BrACHTUNGTRENUNG(ClCHCl2)] (16). The solvento complex 16 is thermally unstable and prone to undergo reductive elimination of C6F5C6F5. In the presence of PhCN, complex [NBu4]- ACHTUNGTRENUNG[trans-PtACHTUNGTRENUNG(C6F5)4BrACHTUNGTRENUNG(NCPh)] (17) was isolated and structurally characterized. The reaction of 3 with I2 gave no organoplatinum( IV) compound. Our comparative study reveals that the CF3 group is especially suited to stabilize organometallic compounds in high oxidation states. This ability can be attributed to a combination of factors: its hardness, its high group electronegativity, its small size, and its reluctance to undergo reductive elimination processes.