Systematics of boron halide complexes with dichalcogenoether ligands - Synthesis, structures and reaction chemistry

The complexes [BX3(m-L L)BX3] (X 1⁄4 Cl, Br, I; L L 1⁄4 EtS(CH2)2SEt, MeSe(CH2)2SeMe), [BX03{oC6H4(SMe)2}] (X’ 1⁄4 Cl, I), [(BBr3)2{o-C6H4(SMe)2}], [(BBr3)2{o-C6H4(SeMe)2}] and [BI3{o-C6H4(SeMe)2}] have been prepared as moisture-sensitive pale solids by reaction of the appropriate BX3 with the dichalcogenoether in anhydrous n-hexane solution, and characterised by microanalysis, IR and multinuclear (1H, 11B, 77Se{1H}) NMR spectroscopy. In contrast, the [BF3(m-L L)BF3], [(BF3)2{o-C6H4(SMe)2}] and [(BF3)2{o-C6H4(SeMe)2}], made from BF3 and the neat ligands, are viscous oils which have a significant vapour pressure of BF3 at ambient temperatures. X-ray crystal structures are reported for [BX3{mEtS(CH2)2SEt}BX3] (X 1⁄4 Cl, Br, I), [BBr3{m-MeSe(CH2)2SeMe}BBr3], [BCl3{o-C6H4(SMe)2}] and [(BBr3)2{m-oC6H4(SeMe)2}]. The complexes [(BX3)2{MeTe(CH2)3TeMe}] (X 1⁄4 F, Cl, Br) have been identified in solution by multinuclear NMR spectroscopy, but decompose rapidly, whilst o-C6H4(TeMe)2 decomposes immediately on contact with BBr3 or BCl3. Dealkylation of some of the chalcogenoether ligands at room temperature by BI3, to yield complexes including [BI2{o-C6H4S(SMe)] and [BI2{o-C6H4Se(SeMe)], has been identified and the X-ray structure of [BI2{o-C6H4Se(SeMe)] determined. The trends in behaviour along the series of boron halides and with the various chalcogenoethers are described and compared with the behaviour of BX3 with neutral phosphorus and arsenic donor ligands (Burt et al., Inorg. Chem., 2016, 55, 8852) and with [BX3(EMe2)] (E 1⁄4 S, Se, Te) (Okio et al., J. Organometal. Chem., 2017, 848, 232). © 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).