Preparation, properties, and crystal and molecular structures of the cyanomethane adducts of niobium(IV) chloride and di-µ-sulphido-bis[dichloroniobium(IV)]

Abstract

The cyanomethane adduct of NbCl₄ analyses for NbCl₄·3CH₃CN (1). A crystal-structure determination of this species shows that it contains cis octahedral [NbCl₄(NCMe)₂] and a solvent CH₃CN molecule. The unique bond lengths are Nb–N 2.220(13)Å and Nb–Cl 2.328(2), 2.343(6), and 2.349(4)Å. The crystals of (1) are orthorhombic with unit-cell dimensions a= 10.437(11), b= 13.883(12), c= 9.828(9)Å, Z= 4, and space group Pnma. A total of 729 reflections above background have been collected on a diffractometer and refined to R 0.051.

When the cyanomethane adducts of NbX₄(X = Cl or Br) are treated with Sb₂S₃ in cyanomethane, adducts of NbX₂S (X = Cl or Br) are formed. The products contain [{NbX₂S(NCMe)₂}₂] in which there is a [graphic omitted] ring. The crystal structures of two compounds, (2) and (3), containing the [{NbCl₂S(NCMe)₂}₂] dimeric unit have been determined. In (2) there are two molecules of occluded CH₃CN for each dimer while (3) has one. Both (2) and (3) are triclinic with space group P, with (2) having a= 9.031 (7), b= 9.367(6), c= 8.360(8)Å, α= 108.72(9), β= 94.93(7), γ= 105.70(8)°, Z= 1 and (3) having a= 14.965(18), b= 8.838(17), c= 9.543(23)Å, α= 112.42(18), β= 84.39(28), γ= 103.65(21)°, Z= 2. For (2), 1 434, and for (3), 1 530, independent reflections above background have been collected on a diffractometer and refined to R 0.056 and 0.050 respectively.

The dimer configurations in (2) and (3) are identical. The niobium atoms are in a pseudo-octahedral environment consisting of two cis sulphur [Nb–S 2.338(8)–2.349(7)Å], two trans chlorine [Nb–Cl 2.383(6)–2.403(5)Å], and two cis nitrogen atoms [Nb–N 2.286(26)–2.334(22)Å]. In addition, in each dimer there is a Nb–Nb single bond [2.862(2)–2.872(3)Å].