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

Abstract 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[NbCl 2 (CO) 4 (py)], 1 , in 75 % yield, with the release of CO and H 2 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 (PhICl 2 ) in CH 2 Cl 2 produced Na[Nb 2 (μ‐Cl) 3 (CO) 8 ] (70 % yield). When the latter reaction was conducted in the presence of phosphines, the niobium(II) adducts [NbCl 2 (PEt 3 ) 4 ], [NbCl 2 (κ 2 ‐dmpe) 2 ] and [NbCl 2 (κ 2 ‐triMeos) 2 ], 2 , respectively, were obtained in 33–70 % yields [dmpe=1,2‐bis(dimethylphosphino)ethane, triMeos=Me 2 PCH 2 {C(Me)(CH 2 PMe 2 )}CH 2 PMe 2 ]. The new complexes 1 and 2 were characterized by elemental analysis, IR or 1 H 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.