Reaction of mesityllithium with SnCl4 (2:1) gives (mesityl)2SnCl2, While the corresponding reaction using mesitylmagnesium bromide gives a mixture of halogenato-products (MeSityl)2SnCl2, (mesityl)2SnBr2 and (mesityl)2SnClBr. Reaction of this latter mixture with SnCl4 (1:1) gives the full range of (mesityl)SnXnY3-n (X = Cl, Y = Br). In contrast, the more sterically demanding carbanion source 2,4,6-iPr3C6H2Li reacts with SnCl4 or SnBr4 (1:1) to give the coupled ditin product (2,4,6-iPr3C6H2)4Sn2(hal)2. The structure of the bromide, [(2,4,6-iPr3C6H2)4Sn2Br2] (Sn-Sn) has been determined and shown to consist of molecular units in an approximately staggered conformation, with an Sn-Sn distance of 2.841(1) angstrom. The molecule is highly sterically congested, leading to non-equivalence of methyl groups in some isopropyl units owing to hindered rotation about C-C and C-Sn bonds.
Selective Preparation of Sterically Encumbered Diaryltin Dihalides from Grignard Reagents via Salt Metathesis and Halide Exchange
作者:Beate G. Steller、Roland C. Fischer
DOI:10.1002/ejic.201900180
日期:2019.6.10
A general route for the selective preparation of diaryltin dichlorides, dibromides, and diiodides from readily accessible but sterically demanding, 2,6‐disubstituted or 2,4,6‐trisubstituted aryl Grignard reagents ArylMgBr and tin tetrachloride was developed. During work‐up, the initially obtained mixture of halides is converted into a single species. The thus obtained diaryltin dichlorides were reacted