Low-Coordinate Bismuth Cations

Chloride
abstraction from the diamido-bismuth compound Bi­(Me2Si­{NAr}2)Cl (1, Ar = 2,6-i-Pr2C6H3) using MCl3 (M
= Al, Ga) is a facile route to cationic species. Stoichiometric reactions
afford the tetrachlorometallate salts [Bi­(Me2Si­{NAr}2)]­[MCl4] (2a, M = Al; 3a, M = Ga), whereas reaction with 0.5 equiv of the group
13 reagent gives the μ-chlorido bridged cations [{Bi­(Me2Si­{NAr}2)}2(μ-Cl)]­[MCl4] (2b, M = Al; 3b, M = Ga). The
crystal structure of 2a shows a formally two-coordinate
bismuth cation, with a Bi···Cl contact to the [AlCl4]− anion, whereas the structure of 3b shows a total of three Bi···Cl contacts
to [GaCl4]−. Both species associate as
{1:1}2 dimers in the solid state through additional Bi···Cl
interactions. Attempted preparation of cationic complexes using either
NaBR4 (R = Ph, Et) or [HNEt3]­[BPh4] were unsuccessful. Instead of forming the borate salts, the neutral
compounds Bi­(Me2Si­{NAr}2)­R (4,
R = Et; 5, R = Ph) were isolated as a result of aryl/alkyl
transfer from boron to bismuth.

以三氯化物MCl₃（M=Al、Ga）对二酰胺基铋化合物Bi(Me₂Si{NAr}₂)Cl（1，Ar=2,6-二异丙基苯基）进行氯抽取反应，是制备阳离子物种的简便合成路径。化学计量比反应可得到四氯金属酸盐[Bi(Me₂Si{NAr}₂)][MCl₄]（2a，M=Al；3a，M=Ga）；当使用0.5当量的第13族试剂进行反应时，则生成μ-氯桥联阳离子[{Bi(Me₂Si{NAr}₂)}₂(μ-Cl)][MCl₄]（2b，M=Al；3b，M=Ga）。2a的晶体结构显示其为形式上的双配位铋阳离子，且存在Bi···Cl与[AlCl₄]⁻阴离子的相互作用；而3b的晶体结构则存在总计三个Bi···Cl与[GaCl₄]⁻阴离子的相互作用。两种物种在固态中均通过额外的Bi···Cl相互作用以{1:1}₂二聚体形式缔合。尝试使用NaBR₄（R=Ph、Et）或[HNEt₃][BPh₄]制备阳离子配合物均未成功，最终并未得到硼酸盐类盐，而是通过芳基/烷基从硼向铋的转移反应，分离得到了中性化合物Bi(Me₂Si{NAr}₂)R（4，R=Et；5，R=Ph）。