Crystal structures of azine derivatives of (η5-acylcyclopentadienyl)dicarbonylnitrosylchromium and unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of azine derivatives of (η5-acylcyclopentadienyl)dicarbonylnitrosylchromium, (η5-a

Azine derivatives—(4), (5), (12), (13)—of (η5-C5H4CHO)Cr(CO)2(NO) (2), (η5-C5H4COCH3)Cr(CO)2(NO) (3), (η5-C5H4CHO)W(CO)3(CH3) (10), and (η5-C5H4COCH3)W(CO)3(CH3) (11) were obtained from condensation reaction of hydrazine with each corresponding carbonyl group. The structures of 4 and 5 were determined by X-ray diffraction studies. The chemical shifts of the C(2)–C(5) carbon atoms of 4, 5, 12, and 13 have been assigned using two-dimensional HETCOR NMR spectroscopy. We observed that C(2,5) resonate at a lower field than C(3,4) in [(CO)2(NO)Cr(η5-C5H4CRN–)]2 (R = H, 4; R = CH3, 5), whereas C(3,4) resonate at a lower field than C(2,5) in [(CO)3(CH3)W(η5-C5H4CRN–)]2 (R = H, 12; R = CH3, 13). The correlation between the magnitudes of nonplanarity of Cp-exocyclic carbon to π-acceptor substituents and the twist angle of NO to Cp-exocyclic carbon are discussed. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of 13C NMR data and those of 4 and 5 are compared with calculations using the density functional B3LYP exchange–correlation method.

Graphical abstractAzine derivatives of CpCr(CO)2(NO), CpMo(CO)3(CH3), and CpW(CO)3(CH3) have been synthesized. Based on 2D HETCOR–NMR, C(3,4) resonates at lower field than C(2,5) on the Cp(Mo,W) azine derivatives, opposite to those of Cp(Cr) analogs. The X-ray structure revealed that E,E-[(CO)2(NO)Cr(η5-C5H4CHN)]2 has a cisoid NO orientation to the exocyclic carbon.Figure optionsDownload full-size imageDownload as PowerPoint slide