Unequivocal assignments of C(2,5) and C(3,4) on the Cp ring of scynichrodene derivatives bearing an electron-donating substituent in 13C NMR spectra and X-ray structures of (CO)2(NO)Cr[(η5-C5H4)-C(O)-(η5-C5H4)]Ru(η5-C5H5) and (CO)2(NO)Cr[(η5-C5H4)–CH2–(η5

Friedel–Crafts acylation of ruthenocene with (η5-chloroformylcyclopentadienyl)dicarbonylnitrosylchromium 15 has afforded cynichrodenyl ruthenocenyl ketone 6 in 39% yield. Reduction of 6 and acetylcynichrodene 11 with lithium aluminum hydride/aluminum chloride leads to cynichrodenylruthenocenylmethane 8 and ethylcynichrodene 2 in 45% and 63% yield, respectively. Structures of compound 6 and 8 have been solved by X-ray diffraction studies. Both cisoid and transoid conformations at the organic carbonyl carbon were observed in 6. The twist angle is 177.2°, 105.8°, 72.3°, and 24.4° for NO ligand of Cp(CO)2(NO) moiety in 5, transoid 6, cisoid 6, and 8, respectively. Compared the HetCOR NMR data of 6–8 with those of their ferrocene analogues, the opposite correlation was observed on the chemical shift assignments of C(2)–C(5) of Cp(Cr) in compound 5 and 6, while the correlation in compound 7 and 8 is the same. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of 13C NMR data and those of 5, 8, and 9 are compared with the calculations via density functional B3LYP correlation-exchange method.

Compounds (CO)2(NO)Cr[(η5-C5H4)–C(O)–(η5-C5H4)]M(η5-C5H5) and (CO)2(NO)Cr[(η5-C5H4)–CH2–(η5-C5H4)]–M(η5-C5H5) (M = Fe, Ru) have been prepared. The qualitative relationship of the NO group orientation and the nonplanarity of Cp-exocylic carbon has been addressed. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of 13C NMR data and compared with calculations via density functional B3LYP correlation-exchange method.Figure optionsDownload as PowerPoint slide