Selective dynamics of [Rh(1,5-COD)(bidentate)]BF4 complexes via NMR exchange spectroscopy

NMR exchange measurements on [Rh(1,5-COD)(bidentate)]BF4 complexes (bidenta te = chiral bis-phosphine, a P,N-phosphinooxazoline, a P,S-phosphito-thioet her and a bis-pyrazolylborate) show selective 1,5-COD dynamics which can be superficially attributed to olefin rotation. It is suggested that the mech anism actually involves: (1) M-L-1 band breaking (L-1 = N or S-donor); (ii) isomerization of the T-shaped species; (iii) rotation around the remaining M-L-2 bond and (iv) recomplexation. The solid state structures of the two compounds [M(1,5-COD)(10)]BF4, M = Rh, Ir and 10 = (S,R)-2-[4-(isopropyl)ox azol-2-yl]-2'-diphenylphosphino-1,1'-binaphthyl, were determined by X-ray d iffraction methods. (C) 1999 Elsevier Science S.A. All rights reserved.