Preparative-scale HPLC Resolution of Metallacyclic η³-Allyltricarbonyliron Complexes and Determination of the Absolute Configuration by X-Ray Crystal Structure Analysis

Abstract

Racemates of (η³-allyl)tricarbonyliron lactone complex Fe(CO)₃{η¹:η³-C(O)XCH₂CHCMeCH₂} 1a (X=O) and (η³-allyl)tricarbonyliron lactam complex 2a (X=NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (–)-2a is determined by X-ray crystal structure analysis.

References

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9. Developed by Prof. A. Werner, University of Vienna; not commercially available yet.
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12. ¹HNMR shift analysis proved to be impracticable for the determination of enantiomeric purity of 3a. Treatment of a racemic sample in CDCl₃ with Eu(hfc)₃(hfc – heptafluoropropylhydroxymethylene D-camphorate) did not lead to any signal separation.
13. 3a: mp. 121 °C; R_f(CH₂Cl₂ CH₃CN, 1∶1) 0.70; ν_max/cm¹ 3040, 2930, 2840, 2020, 1985, 1970, 1445, 1390, 1240; δ_H(CDCl₃ , Me₄Si) 2.16 (3 H, s, 4-Me), 2.83 (3 H, s, NMe), 2.93 (1 H, d, J_5en,5ex 2.1, 5-H^en), 3.63 (1 H, dd, J_2en,2ex 13.7, J_2en,3 2.1, 2-H^en), 3.89 (1 H, dd, J_2en,2ex 1.37, J_2en,3 8.2, 2-H^ex), 3.91 (1 H, d, J_5en,5ex 2.1, 5-H^ex), 4.41 (3 H, s, OMe), 4.84 (1 H, dd, J_3,2ex 8.2, J_2en,3 2.1, 3-H); δ_C(CDCl₃, Me₄Si) 26.9 (4-Me), 35.7 (NMe), 55.1 (C-5), 63.1 (C-2), 65.6 (OMe), 70.7 (C-3), 118.8 (C-4), 203.9, 206.3, 207.2 (FeCO), 222.3 (C-1).