CARBENE FORMATION IN THE REACTIONS OF LFE((CH2)3BR)(CO)2 (L = CP, CP-STAR) WITH I- - X-RAY CRYSTAL-STRUCTURES OF CPFEI(CO)(=C(CH2)3O) AND CPFEI(CO)(=CCME2(CH2)2O) - ANALYSIS OF THE CARBENE ORIENTATIONS

The reaction of LFe{(CH2)3Br|(CO)2 (L = Cp, Cp*) with Lil affords the new carbene complexes LFeI(C0){=C(CH2)3O}, both of which have been characterized spectroscopically; the Cp species has been characterized by X-ray crystallography as well. The unusual feature of the structure of CpFel(CO){=C(CH2)3O} is the presence of two conformers within the unit cell. To a first approximation these are related by a rotation about the Fe=C axis. The reasons for the presence of the two conformers are examined by molecular mechanics and Fenske-Hall type calculations. Treatment of CpFeI(CO){=C(CH2)3O} with LDA followed by Mel results in CpFeI(C0){=CCMe2(CH2)20), whose crystal structure has just the single conformer in the unit cell. © 1990, American Chemical Society. All rights reserved.