The reaction between [Fe3(CO)12] and P(OR)3 (R = Me, Et, or Ph) in the presence of the bimetallic catalyst [{Fe(CO)2(PPh3)(SEt)}2] affords 2 1,2,3-trisubstituted isomers which rapidly interconvert at room temp. on the NMR time-scale. The soln. structures and dynamics were elucidated for both isomers by variable-temp. 31P and 13C NMR studies. In polar solvents the major isomer shows a [Fe3(CO)12]-like structure whereas the minor 1 contains only terminally bonded CO groups. The observation of 3 equally intense carbonyl resonances in the low-temp.-limiting spectra (R = Me or Et) supports a D3 structure for this isomer. The equilibration of axial CO ligands occurs readily as the temp. is increased; this rearrangement may be ascribed to the motion of the Fe3 triangle inside the polyhedral cloud of ligands or alternatively to an interconversion between a left-hand screw with a right-hand screw.
Solution structure and dynamic behavior of two isomers of [Fe3(CO)9{P(OR3)}3] (R = Me, Et, or Ph) derivatives.
AIME, Silvio;BOTTA, Mauro;GAMBINO, Olimpia;GOBETTO, Roberto;
1989-01-01
Abstract
The reaction between [Fe3(CO)12] and P(OR)3 (R = Me, Et, or Ph) in the presence of the bimetallic catalyst [{Fe(CO)2(PPh3)(SEt)}2] affords 2 1,2,3-trisubstituted isomers which rapidly interconvert at room temp. on the NMR time-scale. The soln. structures and dynamics were elucidated for both isomers by variable-temp. 31P and 13C NMR studies. In polar solvents the major isomer shows a [Fe3(CO)12]-like structure whereas the minor 1 contains only terminally bonded CO groups. The observation of 3 equally intense carbonyl resonances in the low-temp.-limiting spectra (R = Me or Et) supports a D3 structure for this isomer. The equilibration of axial CO ligands occurs readily as the temp. is increased; this rearrangement may be ascribed to the motion of the Fe3 triangle inside the polyhedral cloud of ligands or alternatively to an interconversion between a left-hand screw with a right-hand screw.
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