ENTHALPIES OF REACTION OF (BENZYLIDENEACETONE)IRON TRICARBONYL, (BDA)FE(CO)3, WITH PHOSPHINE-LIGANDS - THERMODYNAMIC INSIGHTS INTO IRON CHEMISTRY

The enthalpies of reaction of (BDA)Fe(CO)3 (BDA = benzylideneacetone) with a series of monodentate phosphine ligands (PR3) leading to the formation of trans-(PR3)2Fe(CO)3 complexes have been measured by solution calorimetry in THF at 50-degrees-C. These enthalpy data help establish the following relative order of stability: PEt3 > P(n)Bu3 > PMe3 > PPhMe2 > PPh2Me > PPh3. The data span a range of 15 kcal/mol. This stability scale sheds light on the relative donating ability of phosphines. These data also allow comparison with other organometallic systems and give insight into factors influencing the Fe-PR3 bond disruption enthalpies in the (PR3)2Fe-(CO)3 system.