QUANTITATIVE-ANALYSIS OF LIGAND EFFECTS (QALE) - SYSTEMATIC STUDY OF IRON-PHOSPHORUS BOND LENGTHS AND THEIR RELATIONSHIP TO STERIC THRESHOLDS

Systematic determination of Fe-P bond lengths for the set of complexes (77-Cp)(CO)(L)FeCOMe containing “sterically unencumbered” σ-donor phosphorus(III) ligands shows that the Fe-P bond lengths vary over a narrow range (2.195 ± 0.015 Â) and are only slightly dependent on the σ-donicity and size of the ligand. τ-Acid ligands (i.e. P(OR)3) exhibit significantly shorter Fe-P bond lengths around 2.10 Â. In light of this virtual constancy of σ bond length for a family of complexes, it is reasonable to expect steric thresholds to be manifest. We report on five systems that can be analyzed in terms of sharp thresholds. © 1990, American Chemical Society. All rights reserved.