The relationship between surface derivatization and the physical properties of bisarylphosphinidenetriironnonacarbonyl clusters

Abstract

A series of clusters, Fe-3(CO)(9)(mu(3)-P-p-C6H4X)(mu(3)-P-p-C6H4X') (X = X'= NMe2, OCH3, CH3, Cl, CF3, CN; X = CN, XI = NMe2) has been prepared using functionalized p-XC6H4PCl2 starting materials. The influence of changes in the X groups on the physical properties of the Fe-3(CO)(9) cluster core are examined. This cluster series displays two one-electron reductions to produce stable radical monoanions and diamagnetic dianions, allowing the behavior of all three species to be examined. Infrared, P-31 and H-1 NMR, and electron paramagnetic resonance (of the radical monoanion) spectroscopies as well as the structural characterization of two members of the series, Fe-3(CO)(9)(mu(3)-P-p-C6H4X)(mu(3)-P-p-C6H4X') (X = X' = NMe2; X = CN, X' = NMe2) by single crystal X-ray diffraction methods all indicate that the cluster structures are invariant with the nature of X. The Hammett linear free energy relationship is used to quantify the observed changes in cluster properties. Analysis of infrared, electron paramagnetic resonance and cyclic voltammetry data by the Hammett equation quantify the communication between the cluster surface and the Fe-3(CO)(9) core. Fenske-Hall molecular orbital calculations were used to assess the important orbital interactions between the substituted phenyl rings and the Fe-3(CO)(9) cluster core. (C) 1999 Elsevier Science S.A. All rights reserved.