Ion pair symmetrization in metallocenium cations partnered with diborane derived borate counteranions
摘要:
The thermodynamics of ion pair symmetrization in a series of metallocenium species generated from Cp-2"ZZrMe(2) (Cp" = 1, 2-Me2C5H3) were studied using a variety of solution dynamic techniques including line broadening, 2D-EXSY, and 1D-DPFGSE-NOE. Ion pairs were generated by methide abstraction using the corresponding trityl salts [1-A] to yield [Cp"2ZrMe](+)[A](-) (A = {C6F4-1,2-[B(C6F5)(2)](2)(mu-O(C6F5))}, 2-O(C6F5); {C6F4-1,2-[B(C6F5)(2)](2)(mu-OPh)}-, 2-OPh; {C6F4-1,2-[B(C6F5)(2)](2)(mu-OMe)}(-), 2-OMe; and [B(C6F5)(4)](-), 2-B(C6F5)(4)). The observed activation parameters were interpreted on the basis of a solvent-assisted mechanism of ion pair symmetrization. (C) 2007 Elsevier B.V. All rights reserved.