Synthesis, characterisation and structures of thio-, seleno- and telluro-ether complexes of gallium(iii)

Abstract

The reactions of GaX3 (X = Cl, Br or I) with SMe2, SeMe2 and TeMe2 (L) in non-coordinating solvents produces only the pseudo-tetrahedral [GaX3L], which have been characterised by IR, Raman and multinuclear NMR (1H, 71Ga, 77Se or 125Te) spectroscopy, and by the crystal structure of [GaCl3(SeMe2)]. The 71Ga NMR resonances show small low frequency shifts for fixed halides as the neutral donors change from S --> Se --> Te. Bidentate ligands including MeS(CH2)2SMe, PhS(CH2)2SPh, MeSe(CH2)2SeMe, nBuSe(CH2)2Se(n)Bu and MeTe(CH2)3TeMe (L-L) also produce complexes with 4-coordinate gallium centres, [(GaX3)2(mu-L-L)], confirmed by the crystal structures of [(GaI3)2(mu-MeS(CH2)2SMe)], [(GaCl3)2(mu-PhS(CH2)2SPh)] and [(GaCl3)2(mu-nBuSe(CH2)2Se(n)Bu)]. The structural data are consistent with the weaker Lewis acidity of the gallium as the halide co-ligands become heavier. Multinuclear NMR studies suggest that in chlorocarbon solutions partial dissociation of the ligands occur, which increases with the halide co-ligand Cl < Br < I. The o-xylyl dithioether, o-C6H4(CH2SMe)2, despite being pre-organised for chelation, also forms [(GaCl3)2(mu-L-L)]. The corresponding diselenoether complex decomposes in solution with C-Se bond cleavage to form the selenonium salt [o-C6H4CH2Se(Me)CH2][GaCl4], which was structurally characterised. The ditelluroether o-C6H4(CH2TeMe)2 undergoes rapid C-Te bond fission and rearrangement upon reaction with GaCl3, and the telluronium species [o-C6H4CH2Te(Me)CH2]+ and [MeTe(CH2(o-C6H4)CH2TeMe)2]+ have been identified by ES+ mass spectrometry from their characteristic isotope patterns.

Telluroether and Selenoether Complexes as Single Source Reagents for Low Pressure Chemical Vapor Deposition of Crystalline Ga2Te3 and Ga2Se3 Thin Films

“…The compounds were stored and manipulated in an N 2 purged, dry (<1 ppm H 2 O) glovebox and were characterized by IR, Raman, 1 H, 71 Ga, and 125 Te{ 1 H} NMR spectroscopy, and microanalysis as appropriate, with the data in very good agreement with related complexes, and the multinuclear NMR spectra indicate the complexes remain associated in solution. 20 The crystal structure of 6 shows ( Figure 1 20 This is less than expected based simply upon the difference in covalent radii of Te versus Se (0.25 Å), suggesting that the Ga−Te bonds are stronger than the Ga−Se bonds in these systems; this is in accord with the decreased electronegativity of Te over Se.…”

“…20 All of the complexes containing mono-or simple acyclic dichalcogenoethers adopt distorted tetrahedral coordination environments, with a single chalcogen donor ligand, whereas using macrocyclic tetrathioethers or tetraselenoethers leads to higher chalcogen coordination at Ga, leading to five-or six-coordinate species. 24 While the thioether and selenoether complexes are stable under a dry N 2 -atmosphere, the telluroether complexes are more sensitive.…”

Synthesis and complexation of dichalcogenoethers with cyclopropyl backbones, (CH2EMe)2 (E=Se or Te)

“…In this case the major products were the selenonium species [o-C 6 H 4 (CH 2 ) 2 Se Me]I and [Me 3 Se]I. The cation in the former species has been obtained previously from reaction of the diselenoether with GaCl 3 or InCl 3 [20,21], where it was isolated as [o-C 6 H 4 (CH 2 ) 2 Se Me][MCl 4 ] (M = Ga or In) and characterised by an X-ray structure (Ga salt), its characteristic 77 Se chemical shift and by ES + mass spectrometry. In the present iodide salt the structure (Fig.…”

Trialkylstibine Complexes of Boron, Aluminum, Gallium, and Indium Trihalides: Synthesis, Properties, and Bonding

“…In contrast, thallium(III) halides TlX 3 (X = Cl, Br) are easily reduced, with halogenation of the donor atom; hence, no examples with neutral soft donor ligands have been isolated. 5,19,20 The Lewis acidity of the group 13 halides varies with both M and X. For boron, the Lewis acidity usually increases with X in the order F < Cl < Br < I; 5,21−25 recent computational effort has shown this to be due to the energies of the boron σ-bonding interactions, and hence the long-held view that B−X π-back-bonding is responsible has been discounted.…”