201. The reaction between ammonia and transition-metal halides. Part V. The reaction of ammonia with titanium (IV) bromide and titanium (IV) iodide

Abstract

Fowles and Nicholls : The Reaction between 201. The Reaction between Ammonia and Transition-metal Halides.The Reaction of Ammonia with Titanium(rv) Bromide and Part V.* Titanium(1v) Iodide.By G. W. A. FOWLES and D. NICHOLLS. Titanium(1v) bromide and iodide have been shown to form di-and hexaammoniates when ammonia is passed through their solutions in organic solvents. In liquid ammonia the halides are ammonolysed, titanium(1v) iodide being completely soluble. Ion-exchange studies indicate the formation of complex anionic species of the type [TiX,(NH,),-J2-.A t -36" the compounds TiBr4,8NH, and Ti14,8NH, are formed, and tensimetry indicates that these are mixtures containing mainly TiBr(NH,) , and Ti1 (NH,), respectively.On thermal decomposition, TiBr4,8NH, gives the simple adduct TiBr4,2NH, as a red sublimate, and a residue of TiNBr. TiN is the final product formed by the decomposition of TiI4,8NH,.THE reactions of liquid ammonia with metal halides have recently been studied in some detail. It has, for instance, been shown that titanium(1v) chloride,l vanadium@) chloride,2 and tin(1v) chloride are ammonolysed, and that when the ammonium chloride is removed by washing with liquid ammonia ammonobasic halides of formula MCl(NH,), are produced. Much less is known of the ammonolysis of the corresponding bromides and iodides, however, and nothing of the reaction of ammonia with titanium(1v) iodide. Work on the titanium(1v) bromide-ammonia reaction has been limited to an early investigation by Ruff and his co-workers 495 who obtained a compound TiBr,,8NH3, which when washed with liquid ammonia left a solid of variable composition ; . thermal decomposition of this product at 270" 212 vacuo gave a substance of formula TiNBr.In view of the limitations of Ruff's study we have re-investigated the reaction of ammonia with titanium(1v) bromide, and also examined the analogous titanium(1v) iodide-ammonia reaction. EXPERIMENTALMaterials.-Titanium(1v) bromide was prepared by heating titanium metal sponge with bromine under reflux; excess of bromine was distilled off, and the titanmm(1v) bromide purified by distillation in vacuo (Found: Ti, 13.2; Br, 86-7. Calc. for TiBr,: Ti, 13.0; Br, 87.0%). Titanium(1v) iodide was prepared by heating titanium sponge and excess of iodine under reflux in carbon tetrachloride. After the removal of the excess of iodine and carbon tetrachloride, the titanium(1v) iodide was distilled in vacuo, the final traces of iodine being pumped off a t 100" (Found: Ti, 8.85; I, 91.1. Calc. for Ti14: Ti, 8.62; I, 91.4%). Liquid ammonia was dried over sodium. 2 : 2 : 4-Trimethylpentane was dried (P,OJ; carbon disulphide was shaken with aqueous potassium permanganate to remove hydrogen sulphide and dried (P,O,) . Other reagents, of " AnalaR " grade, were freed from traces of moisture by placing them in a vacuum for several hours immediately before use.Bromine was determined gravimetrically as silver bromide, and iodine by titration with potassium iodate.A naZyses.-Nitrogen and titanium were determined as descr...

Superconducting nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I)

“…The superconducting transition temperature T c ¼ 12 K decreases by 0.06 AE 0.03 K in Li-doped ZrNCl, when 14 N is substituted by 15 N [164]. This small change in T c corresponds to an isotope shift coefficient a ¼ 0.07 AE 0.04, which is much smaller than the value of 0.5 obtained within the conventional BCS theory.…”

“…In both cases the by-products ammonium halides, amide halides like M(NH 2 ) 3 X (M ¼ Ti, Zr; X ¼ Cl, Br) [14,17,18], different ammonia adducts such as MX 4 Á n NH 3 (M ¼ Ti, Zr; X ¼ Cl, Br, I; n ¼ 2, 4,5,6,8) [12,13,17,19,20] and (NH 4 ) 2 [MCl 6 ] (M ¼ Ti, Zr) [21,22] necessitate a purification step, which comprises sublimation or thermal treatment in an ammonia stream at the synthesis temperature (see Table 1). Especially the ammonia adducts and amides were observed as main products at low temperatures (<400 C) [20], while at higher temperatures (>750 C) binary nitrides with several compositions (Zr 3 N 4 , Zr 3 N, ZrN, MN x with M ¼ Ti, Zr) are obtained [19,20,22].…”

Chemistry and superconductivity of intercalated metal nitride halides

“…Intercalated nitride halides of titanium, zirconium or hafnium show superconductivity with critical temperatures up to 25.5 K [1][2][3][4]. The compounds MNX (M = Ti, Zr; X = Cl, Br, I) were initially investigated by Juza et al [5] and Fowles et al [6] who studied the reaction of ammonia with the halides of titanium and zirconium among other transition metals. Zirconium and hafnium nitride halides may crystallize in two structural polymorphs designated as α and β that are isotypic to orthorhombic Pmmn FeOCl and rhombohedral R-3m types, respectively (figure 1).…”

“…If this slab is designated A according to the orientation of the halide atoms then the double slabs are ordered ABC along c (figure 2(a)). The structure of the SmSI polymorph of ZrNCl is derived by occupation of nitrogen atoms of the tetrahedral sites between the zirconium layers (figure 2(b)) with expansion of a-and c-axis to 3.6031 (6) and 27.672(2) Å, respectively, but preserving the R-3m symmetry [9][10][11]. The basal spacing d s defined as 1/3 of the c-axis is 9.235 Å [9].…”