Isolation and X-ray Structure of a Dialkylbismuth(III) Iodo “Nanosquare”: Breaking the Polymeric Mold of R₂BiX

Abstract

We report the synthesis, X-ray structure, and solution behavior of a "nanosquare" formed by four repeating ( i Pr 2 BiI) units. The title complex [ i Pr 2 BiI] 4 (1) formed spontaneously as the major product from the reaction of i Pr 3 Bi with MI 2 (M = Mn, Co, Fe). Complex 1 was then more directly synthesized via bromination of i Pr 3 Bi to form ( i Pr 2 BiBr), followed by iodide substitution. The X-ray structure of 1 exhibited acute Bi−I−Bi bonds (∼85−95°) that enabled formation of the hollow square motif. Synthetic control experiments with R 2 BiX (R = i Pr, Bn; X = I, Br) revealed that the identities of both the halide and bismuth R group are determinants for square formation: the bromo-substituted [ i Pr 2 BiBr] n (2) and benzyl-substituted [Bn 2 BiI] n (3) variants formed only polymers as determined by X-ray crystallography. Density functional theory calculations revealed nearly pure porbital-based bonding molecular orbitals on both iodide and bismuth, facilitating the ∼90°/180°bonding motifs.

2,6‐Diisopropylphenyl‐Substituted Bismuth Compounds: Synthesis, Structure, and Reactivity

“…Repeating the reaction on a milligram scale using BiBr 3 , gives a better yield of 67 %. Halide exchange reactions are well known in aryl and alkyl bismuth chemistry and often applied to obtain iodo bismuthanes [1,11,12,21,32] . Consequently, the (2,6‐di iso propylphenyl)iodobismuthane ( 1‐I ) was prepared by the reaction of 1‐Br with CaI 2 in THF at 20 °C and obtained as deep red crystals from pentane solution in 65 % yield.…”

“…Diaryl halido bismuthanes can be prepared via salt metathesis, [1–4] or redistribution reactions of two equivalents of a triaryl bismuthane and a bismuth trihalides [1,5–10] . Moreover, diaryl bismuth halides of the heavier halogens can be prepared via halogen exchange reactions with alkaline or earth alkaline metal halides and diaryl bismuth halides of lighter halogens [1,11,12] . It is common for bismuth halides to show secondary bonding interactions between bismuth and halogen atoms of neighboring molecules in the solid state [8–10,12–14] .…”

“…[1,[5][6][7][8][9][10] Moreover, diaryl bismuth halides of the heavier halogens can be prepared via halogen exchange reactions with alkaline or earth alkaline metal halides and diaryl bismuth halides of lighter halogens. [1,11,12] It is common for bismuth halides to show secondary bonding interactions between bismuth and halogen atoms of neighboring molecules in the solid state. [8][9][10][12][13][14] The tendency for intermolecular interactions lowers when sterically more demanding substituents are employed.…”

“…[1,11,12] It is common for bismuth halides to show secondary bonding interactions between bismuth and halogen atoms of neighboring molecules in the solid state. [8][9][10][12][13][14] The tendency for intermolecular interactions lowers when sterically more demanding substituents are employed. [2,4] Consequently, steric demand greatly influences the solid state structure of substituted halido bismuthanes.…”

“…Most dialkyl and diaryl halido bismuthanes with low steric bulk around the bismuth center form one dimensional polymeric chains with alternating bismuth and halide atoms. [9,10,[12][13][14] Sterically shielded dialkyl and diaryl halido bismuthanes form monomers, [2,4] dimers [8] or oligomers. [12] The monomeric, 2,6-dimesitylphenyl (Ter) substituted, chloro bismuthane (Ter 2 BiCl) and the polymeric, mesityl (Mes) substituted, bromo bismuthane (Mes 2 BiBr) are shown in Figure 1 as examples.…”