Oxidative Chlorination Reactions of [Nb(CO)6]− in the Presence of N‐ and P‐Donors

The 3 : 1 molar reaction of [Na(thf)3][Nb(CO)6] with pyridinium chloride (PyHCl), in dichloromethane, afforded the niobium(I) pyridine adduct pyH[NbCl2(CO)4(py)], 1, in 75 % yield, with the release of CO and H2 confirmed by gas-chromatography. The same metal product, 1, was also isolated in less than 2 % yield from the reaction of [Na(py)3.5(thf)2.1][Nb(CO)6] with gaseous HCl. Additionally, the reaction of Na[Nb(CO)6] with phenyliodine(III)dichloride (PhICl2) in CH2Cl2 produced Na[Nb2(μ-Cl)3(CO)8] (70 % yield). When the latter reaction was conducted in the presence of phosphines, the niobium(II) adducts [NbCl2(PEt3)4], [NbCl2(κ2-dmpe)2] and [NbCl2(κ2-triMeos)2], 2, respectively, were obtained in 33–70 % yields [dmpe=1,2-bis(dimethylphosphino)ethane, triMeos=Me2PCH2{C(Me)(CH2PMe2)}CH2PMe2]. The new complexes 1 and 2 were characterized by elemental analysis, IR or 1H NMR spectroscopy, and single crystal X-ray diffraction. DFT calculations revealed the superior stability of the experimentally observed structure of 2 (exhibiting trans-Cl ligands), compared to a series of hypothetical isomers.