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

Gurnani, Chitra, Levason, William, Ratnani, Raju, Reid, Gillian and Webster, Michael (2008) Synthesis, characterisation and structures of thio-, seleno- and telluro-ether complexes of gallium(III). Dalton Transactions, 44, 6274. (doi:10.1039/b810005e).

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)2SenBu and MeTe(CH2)3TeMe (L–L) also produce complexes with 4-coordinate gallium centres, [(GaX3)2(-L–L)], confirmed by the crystal structures of [(GaI3)2{-MeS(CH2)2SMe}], [(GaCl3)2{-PhS(CH2)2SPh}] and [(GaCl3)2{-nBuSe(CH2)2SenBu}]. 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(-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.

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Contributors

Author: William Levason

Author: Gillian Reid

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