Toward an Understanding of the Anion Effect in CpRu-Based Diels−Alder Catalysts via PGSE-NMR Measurements
作者:P. G. Anil Kumar、P. S. Pregosin、M. Vallet、G. Bernardinelli、R. F. Jazzar、F. Viton、E. P. Kündig
DOI:10.1021/om049559o
日期:2004.11.1
The rate dependence of the [Ru(eta(5)-C5H5)(BIPHOP-F)(acetone)][Y]-catalyzed Diels-Alder reaction of cyclopentadiene with methacrolein on the anion, Y, is shown to be due to selective ion pairing. Pulsed gradient spin-echo (PGSE) diffusion measurements on the model Cp and indenyl complexes [Ru(eta(5)-C5H5)(CH2=CH-CN)(BIPHOP-F)][Y], Y = BF4 and BArF, and [Ru(eta(5)-C9H7)(CH2=CH-CN)(BIPHOP-F)][Y], Y = BF4 and BArF, respectively, combined with H-1-F-19 HOESY NMR data can be used to understand how the ion pairing for the BF4 anion differs relative to that of the BArF anion. Solid-state structures for [Ru(eta(5)-C5H5)(CH2=CH-CN)(BIPHOP-F)][BF4] and [Ru(eta(5)=C5H5)(CH2=CH-CN)(BIPHOP-F)][BArF] are reported and support the NMR solution data. The model carbonyl complexes [Ru(eta(5)=C5H5)(BIPHOP-F)-(CO)][Y], 8 (Y = BF4, SbF6, and BArF) have been synthesized. The IR CO stretching frequencies for 8 showed little variation with anion, thereby proving that the anions do not affect the Lewis acidity of the salts.