The structure of hyperalkaline aqueous solutions containing high concentrations of gallium – a solution X-ray diffraction and computational study

Abstract

Highly concentrated alkaline NaOH/Ga(OH) 3 solutions with 1.18 M Ga(III) T 2.32 M and 2.4 M NaOH T 4.9 M (where the subscript T denotes total or analytical concentrations) have been prepared and investigated by solution X -ray diffraction and also by ab initio quantum chemical calculations. The data obtained are consistent with the presence of only one predominant Ga(III)-bearing species in these solutions, that is the tetrahedral hydroxo complex Ga(OH) 4 -. This finding is in stark contrast to that found for Al(III)-containing solutions of similar concentrations, in which, besides the monomeric complex, an oxo-bridged dimer was also found to form. From the solution X -ray diffraction measurements, the formation of the dimeric (OH) 3 Ga-O-Ga(OH) 3 2-could not unambiguously be shown, however, from the comparison of experimental IR, Raman and 71 Ga NMR spectra with calculated ones, its formation can be safely excluded. Moreover, higher mononuclear stepwise hydroxo complexes, like Ga(OH) 6 3-, that have been claimed to exist by others in the literature, was not possible to experimentally detect in these solutions with any of the spectroscopic techniques used.

Speciation and structure of tin(ii) in hyper-alkaline aqueous solution

“…In spite of these hurdles, the number of publications dealing with this particular aspect of solution chemistry steadily increases. For obvious reasons, metal ions with reasonable solubility (e.g., amphoteric ones) are most 50 intensely studied (e.g., Al(III) [7][8][9] , Ga(III) 10,11 , Cr(III) 12, 13 , Pb(II) 14 , Tl(I) 15,16 , etc.). Beside these, data for metal ions that are hardly soluble in alkaline conditions also emerge (e.g., Cu(II) 17 , Fe(III) 18 , actinides 19 , etc.)…”

“…For obvious reasons, metal ions with reasonable solubility, e.g. amphoteric ones, are most intensely studied including aluminum(III), [7][8][9] gallium(III), 10,11 chromium(III), 12,13 lead(II) 14 and thallium(I). 15,16 Besides these, data for metal ions that are hardly soluble under alkaline conditions have also emerged e.g.…”

Synthesis, Structure, and Selected Properties of Aluminum-, Gallium-, and Indium-Based Metal-Organic Frameworks

“…In comparison to this only few results on the investigation of the aqueous Ga 3+ chemistry have been published [30]. Similar to aluminum, Ga 3+ can also form condensed polyoxogallate clusters (Ga 13 ) [31,32], and also dimers of corner-sharing tetrahedra [Ga 2 O(OH) 6 ] 2− have been observed [33]. In its complexes it is mostly found as isolated GaO 4 and GaO 6 polyhedra depending on the pH of the solution.…”

Selective etching of focused gallium ion beam implanted regions from silicon as a nanofabrication method

“…It was seen that at room-temperature 1 mol L −1 KOH solution does not readily dissolve gallium metal pieces, whereas Ga 2 O 3 powder is soluble. The difference is obviously due to the fact that the oxidation state (III) of gallium in the oxide is the same as in the most likely solvated gallium ion in the strongly basic solutions, the complex anion [Ga(OH) 4 ] − [26]. For Ga metal, an oxidizer is needed to promote dissolution.…”

“…On the other hand, the ability to make spatially well-controlled gallium implanted regions is the basis of gallium resistless lithography. In this method, gallium implantation has been used to create etch masks for KOH wet etching [22][23][24], and deep reactive-ion etching [25,26], for example, though with the issues related to the gallium segregation in the implanted mask areas.…”