Abstract
A conformational analysis for the complex [(ν5-C5H5)Fe(CO)(PPh3)COC H3] based on extended Huckel and ab initio SCF MO calculations is described which indicates that the conformational preference for the acyl oxygen is approximately anti periplanar to CO due to steric interactions between the acyl llgand and two of the phenyl groups of the triphenylphosphine.
| Original language | English |
|---|---|
| Pages (from-to) | 619-622 |
| Number of pages | 4 |
| Journal | Tetrahedron Letters |
| Volume | 27 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 1 Jan 1986 |
Funding
of these phenyl rings in l_,a djacent to the acyl ligand, were modelled by a pair of ethylene molecules with geometries based upon the crystallographics tructural data.' The anti-conformer is calculated to be 8.3 kcal mol-' more stable than the -syn-conformer for this model, in accord with the experimentally observed preference. The above conformational analysis for the acetyl complex 1 allows the following conclusions to be made: (1) it is the steric interaction between the acetyl ligand and one of the phenyl groups of PPh, that is responsible for the acetyl group preferring to be in the plane containing the iron atom, carbon monoxide and the acetyl-carbonyl-carbon,a nd (2) it is the steric interaction between the acetyl ligand and a second phenyl group that is responsible for the anti carbonyl-oxygen to CO conformation being preferred. This conformational analysis is also applicable to the general acyl complexes [(n5-C,H,)Fe(CO)(PPh,)CORw]h ere the anti conformational preference will be more pronounced the larger the group; it is equally applicable to alkoxycarbene and alkoxyvinyl complexes of [(n5-C,H,)Fe(CO)(PPh~)]w here a conformational preference for alkoxy-oxygen anti to CO is also observed." Consideration of this second phenyl group is expected to influence considerably the conformational analysis of the alkyl complexes [(n5-C,H,)Fe(CO)(PPh,)Alw hich we have previously based on PPhH, as a model for PPh,. More detailed --ab initio calculations for both acyl and alkyl complexes are presently being undertaken. Acknowledgement: JIS thanks Philip Morris for providing sabbatical leave and IHW thanks the Royal Society for a Pickering Research Fellowship.
ASJC Scopus subject areas
- Biochemistry
- Drug Discovery
- Organic Chemistry
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