Crystal structures of [η5-C5H4CR(SCH2)2]Cr(NO)2X (R = H, X = Cl or I; R = CH3, X = Cl) and unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of dicarbonyl(η5-cyclopentadienyl)nitrosylchromium, chloro(η5-cyclopentadienyl)dinitrosylchromium, (η5-cyclopentadienyl)iododinitrosylchromium, and (η5-cyclopentadienyl)methyldinitrosylchromium, bearing an electron-donating substituent via induction in 13C NMR spectra

Abstract

After thioacetalization with 1,2-ethanedithiol complexes (η5-C5H4COR)Cr(CO)2(NO) (R=H, CH3) were converted to [η5-C5H4CR(SCH2)2]Cr(CO)2(NO). Chlorination/nitrosylation of the latter with hydrogen chloride/isoamyl nitrite gave [η5-C5H4CR(SCH2)2]Cr(NO)2Cl (R=H 2f, CH32g). Those complexes were converted to iodide analog, [η5-C5H4CR(SCH2)2]Cr(NO)2I (R=H 3f, CH33g) with potassium iodide. The diastereotopism of the two sets of methylene hydrogens on the dithiolanyl substituent was observed in 1H NMR spectra of 2f and 3f, but not in those of 2g and 3g. The environmental disparity revealed by X-ray structures may account for it. Based on the 2D HETCOR, the H(2,5) resonates at a lower field than H(3,4) on the Cp(Cr) ring in 3g, as ferrocene analog (η5-C5H4CH2CH3)FeCp, opposite to CpCr(CO)2(NO) analog (η5-C5H4CH2CH3)Cr(CO)2(NO). The electron density distribution in the cyclopentadienyl ring was discussed on the basis of 13C NMR data and was compared with calculations using the density functional B3LYP exchange–correlation method for those with X-ray diffraction studies.