Abstract
The X-ray crystal structure and absolute configuration of (−) 436-(η 5-C 5H 5)Fe(CO)(CH 3CO)[Ph 2PNHCH(Me)(Ph)] have been determined from single crystal diffraction data. The compound crystallizes in the monoclinic space group P2 1 with two molecules in a unit cell of dimensions a = 10.676(4), b = 8.913(7), c = 13.275(9) Å, and β = 91.36°. The structure was solved by the Patterson method and refined to a final R value of 4.7% using 2299 independent data. The iron atom has distorted octahedral coordination, and the configuration at the iron is found to be ( S) for the (−) 436 diastereoisomer. The FeCp distances average 2.131 Å, with an Fe-(ring centroid)distance of 1.76 Å. The Fe-acetyl distance is virtually identical to that found in another iron/acetyl complex, but shows substantial variation from other compounds where the nature of the C(O)R group is changed. Comparison to the Mo-alkyl/Mo-acetyl series is made, and the argument for back-donation in transition metal acyls is strengthened. The orientation of the acetyl group is determined by a strong NH⋯O intra-molecular hydrogen bond having an N⋯O separation of only 2.86 ». The phosphine ligand has a very short FeP bond which could be in part caused by the role of the adjacent nitrogen in hydrogen bonding. The remaining ligand geometry is the same as that found in a recently reported ruthenium structure, although the absolute configurations at the chiral carbons are reversed, with the current compound being designated ( S) at this site.
Published Version
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