SYNTHESES, CHARACTERIZATION, AND NUCLEOPHILIC SUBSTITUTION-ADDITION REACTIONS OF MANGANESE-OXAPENTADIENYL COMPOUNDS - STRUCTURAL CHARACTERIZATION OF (ETA-5-CH2CHCHCOCH3)MN(CO)2L (L = CO, PPH3) AND THE 1ST ISOLATION OF NOVEL ETA-5-1-AZAPENTADIENYL COMPLEXES

Manganese-Œƞ5-oxapentadienyl compounds (Œƞ5-CH2CHCHCOR)Mn(CO)3 (R = OCH3 (3a), CH3 (3b)) are produced from a refluxing cyclohexane solution of Mn(CO)5(Œƞ1-CH2CH=CHCOR) (R = OCH3 (1a), CH3(1b)). In a heated cyclohexane solution, 3a and 3b react with 1 equiv of tertiary phosphine to afford (Œƞ5-CH2CHCHCOR)Mn(CO)2(PR3) (PR3 = PMe3, PPh3; R = OMe, Me). This phosphine substitution reaction proceeds via an ƞ3-allyl species, and the intermediates (Œƞ3-CH2CHCHCOOCH3)Mn(CO)3P (P = PMe3, PPh3) have been isolated and fully characterized. In polar solvents, 3a takes up one solvent molecule to form (η3-CH2CHCHCOOCH3) Mn(CO)3L (L = CH3CN (6a), acetone (6b), THF (6c)). In CHC13 or CH2C12, 6b and 6c readily lose the ligating solvent and rearrange to 3a. In the presence of BF3-(C2H5)20,3b reacts with the primary amine RNH2 at -78 °C to yield the first isolable 1-azapentadienyl complexes (ηδ-CH2CHCHC(CH3)NR)Mn(CO)3 (R = (CH3)2CH (7a), (CH3)3C (7b)). For 7a and 7b, spectroscopic data in support of η5metal-ligand bonding are presented. For the manganese 1-oxa- and 1-azapentadienyl complexes above, oscillation of the metal-ligand bond has been observed by variable-temperature1H, 13C, and 31PNMR spectra. The molecular structures of 3b and its PPh3-substitution derivative (4d) have been determined by X-ray diffraction to have the following parameters: for 3b, space group P21/c, α = 9.378 (6) k,b = 6.060 (4) A, c = 16.244 (9) λ,β = 91.08 (5)°, Ζ= 4, R= 0.0326, and Äw = 0.0369; for 4d, space group P2!/c, α = 10.0814 (11) k,b = 10.0560 (11) Å, c = 43.892 (5) Å,β = 93.182 (9)°, Ζ= 8, R= 0.045, and Äw = 0.031. © 1990, American Chemical Society. All rights reserved.