Cyclopentadienyl chromium complexes with halide, methyl, isothiocyanate and isoselenocyanate ligands: Structures of [η5-(C5H4-COOCH3)]Cr(NO)2(Br) and [η5-(C5H4-COOCH3)]Cr(NO)2(NCS)

Novel compounds, [η5-(C5H4-COOCH3)]Cr(NO)2(X) (X = Br, NCS, NCSe), have been prepared. The qualitative relationship of the NO group orientation and the nonplanarity of Cp-exocylic carbon has been addressed. The chemical shifts of C(2) and C(5) of Cp rings were unequivocally assigned using two-dimensional HetCOR-NMR spectroscopy. 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.