Greenacre, Victoria, Levason, William and Reid, Gillian (2018) Trialkylstibine complexes of boron, aluminum, gallium, and indium trihalides: synthesis, properties, and bonding. Organometallics, 37 (13), 2123-2135. (doi:10.1021/acs.organomet.8b00265).
Abstract
The reaction of BX3 (X = Cl, Br, I) with SbR3 (R = Et,iPr) in anhydrous hexane or toluene produced moisture-sensitive [BX3(SbR3)], whose stability increases with halide: Cl < Br < I. Unstable [BF3(SbR3)] species were also characterized spectroscopically but lose BF3 very readily. The [MX3(SbR3)] (M = Al, Ga, In) complexes were isolated from hexane solution; the Ga and In complexes can be recrystallized unchanged from CH2Cl2, but [AlX′3(SbR3)] (X′ = Br, I) undergoes X′/Cl exchange with the solvent. The new complexes were characterized by IR and multinuclear NMR spectroscopy (1H, 13C{1H}, 11B, 27Al, 71Ga, 115In, as appropriate). X-ray crystal structures are reported for [BX3(SbR3)] (X = Br, I; R = Et, iPr; X = Cl, R = iPr), [AlI3(SbiPr3)], [GaX3(SbR3)] (X = Cl, I; R = iPr), [GaBr3(SbEt3)], and [InX3(SbR3)] (X = Cl, I; R = Et, iPr); all contain pseudotetrahedral geometries at both the group 13 and antimony atoms, and comparisons with phosphine and arsine analogues are discussed. The donor–acceptor bond lengths are unexceptional, but coordination of the stibine is accompanied by a significant widening of the C–Sb–C angles and a small reduction in C–Sb distances. DFT calculations confirm these results from significant changes in the antimony 5s and 5p contributions to the Sb–C bonds, with corresponding increases in the 5p character of the antimony-based “lone pair” on coordination. Intermolecular hypervalent Cl···Sb interactions are present in the two [InCl3(SbR3)] complexes but absent in the others.
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