Unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of dicarbonyl(η5-cyclopentadienyl)nitrosylchromium, dicarbonyl(η5-cyclopentadienyl)cobalt, and tricarbonyl(η5-cyclopentadienyl)methyltungsten derivatives bearing an electron-withdra

The chemical shifts of C(2)–C(5) carbon atoms of the series of substituted-cyclopentadienyl Cp(M) derivatives—(CO)2Co[η5-(C5H4-sub)] (1–5), (C4Ph4)Co[η5-(C5H4COOCH3)] (6), (CO)3(CH3)W[η5-(C5H4-sub)](7–9), (CO)3(Cl)W[η5-(C5H4COOCH3)] (10), (CO)2(NO)Cr[η5-(C5H4-sub)] (11–23), and (NO)2(Cl)Cr[η5-(C5H4COOCH3)] (24)—have been assigned using two-dimensional HETCOR NMR spectroscopy. The assigned chemical shifts were compared with the NMR data of their ferrocene analogs. We observed that H(3,4) resonate at a lower field than H(2,5) resonate in (CO)2Co(η5-C5H4CHO) 1. The structure of (CO)3(CH3)W[η5-(C5H4COCH3)] 8 has been determined by X-ray diffraction studies. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of 13C NMR data and that of 10 and (CO)2Co[η5-(C5H4COONS)] (NS = N-succinimidyl) (25) is compared with calculations using the density functional B3LYP exchange-correlation method.

Graphical abstractThe chemical shifts of C(2)–C(5) carbon atoms of the series of substituted-cyclopentadienyl Cp(M) derivatives—(CO)2Co[η5-(C5H4-sub)], (CO)3(CH3)W[η5-(C5H4-sub)], and (CO)2(NO)Cr[η5-(C5H4-sub)]—have been assigned using 2D HETCOR NMR. We observed that H(3,4) resonate at a lower field than H(2,5) resonate in (CO)2Co[η5-(C5H4CHO)] 1.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► H(3,4) resonate at lower field than H(2,5) resonate in (CO)2Co(η5-C5H4CHO)]. ► Some new (CO)2(NO)CrCp (1) derivatives were prepared and characterized. ► Spectral comparisons between 1, FcH, and (CO)2CoCp derivatives are presented. ► Comparisons between 1 and (CO)3(CH3)WCp derivatives are also presented. ► 13C assignments correlated well with the data obtained from ab initio calculations.