Crystal structure of (CO)_3(CH_3)Mo[(η~5-C_5H_4)C(CH_3)=N-N=C(CH_3)(η~5-C_5H_4)]Mo(CO)_3(CH_3) and unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of cynichrodene, tricarbonyl(η~5-cyclopentadienyl)methylmolybdenum, tricarbonyl(η~5-cyclopentadienyl)methyltungsten, ferrocene, and dicarbonyl(η~5-cyclopentadienyl)cobalt derivatives bearing an electron-withdrawing carbonyl substituent in ~(13)C NMR spectra

摘要

Schiff's bases (η~5-formylcyclopentadienyl)tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone (6), (η~5-acetylcyclopentadienyl)tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone (7), and (η~5-acetylcyclopentadienyl)tricarbonylmethylmolybdenum azine (8) were obtained from condensation reaction of (CO)_3(CH_3)Mo(C_5H_4CHO) (3) or (CO)_3(CH_3)Mo(C_5H_4COCH_3) (4) with each corresponding primary amine. The structures of 7 and 8 were determined by X-ray diffraction studies. The chemical shifts of C(2)-C(5) carbon atoms of the series of substituted-cyclopentadienyl Cp(M) derivatives-(CO)_2(NO)M[η~5-(C_5H_4COOCH_3)] (1 M = Cr, 2 M = Mo), (CO)_3(CH_3)Mo[η~5-(C_5H_4-sub)] (3-5, 6, 7, 8)-have been assigned using two-dimensional HetCOR NMR spectroscopy. The assigned chemical shifts were compared with the NMR data of other organometallic Cp(M) analogs, (CO)_2(NO)CrCp, (CO)_3(CH_3)WCp, Cp_2Fe, and (CO)_2CoCp. We observed that C(3,4) resonate at a lower field than C(2,5) in (CO)_3(CH_3)Mo[η~5-(C_5H_4CHO)] 3 and 4, whereas C(2,5) resonate at a lower field than C(3,4) in (CO)_3(CH_3) Mo[η~5-(C_5H_4COOCH_3)] 5. The correlation between the magnitudes of nonplanarity of Cp-exocyclic carbon to π-acceptor substituents and the extent of deshielding on the C(3,4) of the Cp ring was discussed. The electron density distribution in the cyclopentadienyl ring was discussed on the basis of ~(13)C NMR data and those of 4, 7, and 8 were compared with calculations using the density functional B3LYP exchangecorrelation method.