22943-66-4Relevant articles and documents
Trimethylphosphine Complexes of Niobium(IV) and Tantalum(IV). Crystal, Molecular, and Electronic Structures of (M = Nb or Ta)
Boyd, Peter D. W.,Nielsen, Alastair J.,Rickard, Clifton E. F.
, p. 307 - 314 (1987)
Reaction of or (thf = tetrahydrofuran) with three equivalents of PMe3 gives the seven-co-ordinate complex .In refluxing benzene this complex converts to which is obtained in good yield by reacting with two equivalents of PMe3. reacts with one equivalent of PMe3 in acetonitrile to give n>. was obtained by reacting dilithium t-butyl-phosphide and PMe3 with TaCl5.Reduction of TaCl5 with Na-Hg amalgam in the presence of Cl gave 2.X-ray structure determinations show the complexes (M = Ta or Nb) are isostructural (space group Im3), containing four symmetrical chlorine bridges across two metal centres each of which have co-ordinated two terminal chlorines and two terminal phosphine ligands .Scattered wave Xα calculations on the electronic structure of the dinuclear complexes (M = Nb or Ta) indicate the formation of a metal-metal single ? bond between the metal atom dz2 orbitals.THe ?-?* energy separation suggests greater metal-metal interaction for the tantalum complex.
A study of the stereochemistry and magnetic and spectral properties of coordination compounds of the niobium(IV) and tantalum(IV) chlorides and bromides and of the complex anions NbCl62- and NbBr62-
Fowles,Tidmarsh,Walton
, p. 631 - 638 (2008/10/08)
Coordination complexes of the types NbX4·2L and MX4·B, where M = Nb or Ta; X = Cl or Br; L = acetonitrile, tetrahydrofuran, tetrahydropyran, or 1,4-dioxane; and B = 2,2′-bipyridyl or 1,10-phenanthroline have been prepared from the tetrahalides. The acetonitrile complexes NbX4·2CH3CN are useful starting materials for the preparation of the hexahalo salts [(C2H5)4N]2NbX6. The far-infrared spectra (500-200 cm-1) of the solid complexes NbX4·2L and MX4·B have been recorded and the metal-halogen stretching frequencies assigned. Interpretation of the latter indicates that these complexes have a cis-octahedral structure; for MX4·B, the chelating nature of the ligand molecules would in any case make this the most likely structure. The diffuse-reflectance spectra and temperature range magnetic properties of all of the niobium(IV) complexes are compared with related measurements on the model octahedral species NbX62-. These spectral measurements allow a fairly straightforward assignment of the halogen(π) → Nb(d) and d ? d transitions whereas the behavior of the magnetic properties of the complexes over the temperature range 300-80°K is not generally well understood.
