Solution thermochemical study of ligand substitution reactions of hybrid alkyl/fluoroalkoxy phosphorus ligands in the L2Fe(CO)(3) system

The enthalpies of reaction of (BDA)Fe(CO), BDA = (C6H5CH=CHC(O)CH3 benzylideneacetone) with a series of novel fluorinated phosphine ligands, PR,OR, (R = Ph, Pr-1, Cy; R-r = (CH2)(2)(CF2)(5)CF3) and (R1O)(2)PCH2CH2P(ORf)(2) (dOR(f)pe), leading to the formation of L2Fe(CO)(3) complexes (L=PR2ORf) have been measured by solution calorimetry in THF at 50 degrees C. Remarkably, reaction enthalpies are essentially invariant over this series of ligands, despite the differing steric and electronic properties of the phosphorus ligands. Carbonyl stretching frequencies help in the estimation of useful electronic parameters associated with the novel phosphorus ligand series. (C) 1999 Elsevier Science S.A. All rights reserved.