Static and Dynamic Structures of InBr_x (x = 1.4, 1.5, 1.75, and 2) Studied by ⁸¹Br NQR and ¹¹⁵In NMR

Abstract

Structure and bonding properties of InBr x (In 5 Br 7 , In 2 Br 3 , In 4 Br 7 and InBr 2 )were studied by 81Br and 115 In NQR, and 115 In NMR. The ethane-like [Br 3 In II -In II Br 3 ] 2 anion was confirmed in In 5 Br 7 or In 2 Br 3 by 81 Br NQR and the anion was characterized by the high quadrupole coupling constant at the 115 In site (e 2 Qq/h ≈ 350 MHz). On the other hand, In 4 Br 7 showed successive phase transitions and was characterized as [In I ] 5 [In III Br 4 ] 2 [In III Br 6 ] by means of 81 Br NQR and 115 In NMR below 370 K. A disordered structure at the cationic sublattice was supposed at Phase I above 370 K. NMR signals assigned to the In I could not be detected for the powdered sample, however, all quadrupole coupling constants ( e 2 Qq/h) and chemical shifts (δ iso ) could be determined using a single crystal. The In I sites show relatively large e 2 Qq/h and also show larger distribution of the chemical shift suggesting a diversity of the In I coordination similar to the isoelectronic main group elements such as Sn II or Sb III .