Abstract
The dihydrogen hydrido complex [FeH(H2)(PP3)] + 1 (PP3 = P(CH2CH2PMe 2)3 2) was formed by the protonation of the dihydrido complex FeH2(PP3) 3 with methanol or ethanol. The observation of H-D coupling in partially deuterated isotopomers of 1 and measurement of T1 relaxation times for the hydrido and dihydrogen resonances of 1 confirmed the presence of the η2-dihydrogen ligand. Complex 1 shows dynamic NMR behaviour in both the 31P and H NMR spectra with facile exchange between the protons in the η2- dihydrogen ligand and the η1-hydrido ligand. The dihydrogen ligand of 1 is easily displaced by both anionic and neutral ligands to afford the corresponding hydrido complexes [FeHX(PP3)]+ (X = CO 11, X = PPh3 12) or FeHX(PP3) (X = Cl 13, X = Br 14, X = 115, X = N3 116). Small quantities of the alkoxy hydrido complexes FeH(OR)(PP3) (R = Me 4; R = Et 5) are observed in methanol and ethanol solutions containing 1. In methanol solution, FeH(OMe)(PP3) 4 reacts to form the carbonyl hydrido complex [FeH(CO)(PP3)] - 11 and isotopic labelling confirms that the carbonyl ligand of 11 is derived from the methanol solvent. The mechanism of methanol oxidation presumably proceeds through β-hydride elimination from FeH(OMe)(PP 3) to produce formaldehyde as an intermediate which is further dehydrogenated to form the carbonyl ligand. [FeH(H2)(PP 3)]+ 1 and FeHC1(PP3) 13 react rapidly with paraformaldehyde to also form [FeMe(CO)(PP3)]+ 11. Complex 11 also decarbonylates acetaldehyde to afford the methyl carbonyl complex [FeMe(CO)(PP3)]+ 17. The structure of 17 was confirmed by X-ray crystallography.
Original language | English |
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Pages (from-to) | 1418-1423 |
Number of pages | 6 |
Journal | Dalton Transactions |
Issue number | 9 |
DOIs | |
Publication status | Published - 23 Apr 2004 |
Externally published | Yes |
Keywords
- Hydrides
- Iron
- Molecular hydrogen complexes
- Nmr spectroscopy
- P-containing ligands