Intramolecular Dynamics of Five-coordinate iron Carbonyl Complexes with olefinic ligands as studied by variable-pressure 1H-NMR spectroscopy |
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| Authors: | Jacques Ioset Lothar Helm Andr Merbach Raymond Roulet Fabrizia Grepioni Dario Braga |
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| Institution: | Jacques Ioset,Lothar Helm,André Merbach,Raymond Roulet,Fabrizia Grepioni,Dario Braga |
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| Abstract: | Variable-pressure 1H-NMR Spectroscopy has been used to study the fluxionality of some five-coordinated Fe complexes in solution. For Fe(CO)2 1,3-cyclooctadiene (PPh3)], the CO site exchange is known (by analogy with Fe(CO)3(1,3-cyclooctadiene)]) to be a non-dissociative process, and an activation volume of ca. 0 cm3.mol?1 was indeed obtained. However, for Fe(CO2){2,3-η:O-σ-(7,7-dimethoxybicyclo2.2.1]hept-2-ene)}(PPh3)], the activation volume of +5 cm3 mol?1 suggests that an unprecedented dissociation process is responsible for the CO site exchange. The molecular structure of Fe(CO)2(1,3-cyclooctadiene)(PPh3)] was ascertained by single-crystal X-ray diffractometry. The crystals are triclinic, space group P1 , a = 9.606(3), b = 16.795(2), c = 7.743(8) Å, α = 97.83(4), β = 109.63(4), γ = 83.37(2)°. The structure determination has shown that the complex possesses a tetragonal pyramidal coordination, with the endocyclic C?C bond and PPh3 occupying basal sites. |
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