Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
J Am Chem Soc. 2019 Apr 17;141(15):6375-6384. doi: 10.1021/jacs.9b01475. Epub 2019 Apr 8.
Reduction of phosphoric acid (HPO) or tetra- n-butylammonium bisulfate ([TBA][HSO]) with trichlorosilane leads to the formation of the bis(trichlorosilyl)phosphide ([P(SiCl)], 1) and trichlorosilylsulfide ([ClSiS], 2) anions, respectively. Balanced equations for the formation of the TBA salts of anions 1 and 2 were formulated based on the identification of hexachlorodisiloxane and hydrogen gas as byproducts arising from these reductive processes: i) [HPO] + 10HSiCl → 1 + 4O(SiCl) + 6H for P and ii) [HSO] + 9HSiCl → 2 + 4O(SiCl) + 5H for S. Hydrogen gas was identified by its subsequent use to hydrogenate an alkene ((-)-terpinen-4-ol) using Crabtree's catalyst ([(COD)Ir(py)(PCy)][PF], COD = 1,5-cyclooctadiene, py = pyridine, Cy = cyclohexyl). Phosphide 1 was generated in situ by the reaction of phosphoric acid and trichlorosilane and used to convert an alkyl chloride (1-chlorooctane) to the corresponding primary phosphine, which was isolated in 41% yield. Anion 1 was also prepared from [TBA][HPO] and isolated in 62% yield on a gram scale. Treatment of [TBA]1 with an excess of benzyl chloride leads to the formation of tetrabenzylphosphonium chloride, which was isolated in 61% yield. Sulfide 2 was used as a thionation reagent, converting benzophenone to thiobenzophenone in 62% yield. It also converted benzyl bromide to benzyl mercaptan in 55% yield. The TBA salt of trimetaphosphate ([TBA][PO]·2HO), also a precursor to anion 1, was found to react with either trichlorosilane or silicon(IV) chloride to provide bis(trimetaphosphate)silicate, [TBA][Si(PO)], characterized by NMR spectroscopy, X-ray crystallography, and elemental analysis. Trichlorosilane reduction of [TBA][Si(PO)] also provided anion 1. The electronic structures of 1 and 2 were investigated using a suite of theoretical methods; the computational studies suggest that the trichlorosilyl ligand is a good π-acceptor and forms σ-bonds with a high degree of s character.
三氯硅烷将磷酸（HPO）或四丁基鏻硫酸氢酯（[TBA][HSO]）还原，分别生成双（三氯硅基）磷化物([P(SiCl)]，1)和三氯硅基硫醚([ClSiS]，2)阴离子。基于六氯二硅氧烷和氢气作为这些还原过程中产生的副产物的鉴定，提出了形成阴离子 1 和 2 的 TBA 盐的平衡方程式：i）[HPO]+10HSiCl→1+4O(SiCl)+6H 用于 P 和 ii）[HSO]+9HSiCl→2+4O(SiCl)+5H 用于 S。氢气通过其随后用于使用 Crabtree 催化剂([(COD)Ir(py)(PCy)][PF]，COD=1,5-环辛二烯，py=吡啶，Cy=环己基)氢化烯烃((-)-松油醇-4-醇)而被识别。磷化物 1 通过磷酸和三氯硅烷的反应原位生成，并用于将烷基氯（1-氯辛烷）转化为相应的伯膦，该伯膦以 41%的产率分离得到。阴离子 1 也可由[TBA][HPO]制备，并在克级规模下以 62%的产率分离得到。用过量的氯化苄处理[TBA]1 会形成四苄基氯化磷，该产物以 61%的产率分离得到。硫醚 2 用作硫代试剂，将二苯甲酮转化为 62%产率的硫代二苯甲酮。它还将苄基溴转化为 55%产率的苄基硫醇。三偏磷酸盐([TBA][PO]·2HO)的 TBA 盐，也是阴离子 1 的前体，被发现与三氯硅烷或四氯化硅反应，提供双(三偏磷酸盐)硅酸盐，[TBA][Si(PO)]，通过 NMR 光谱、X 射线晶体学和元素分析进行了表征。三氯硅烷还原[TBA][Si(PO)]也提供了阴离子 1。使用一系列理论方法研究了 1 和 2 的电子结构；计算研究表明，三氯硅基配体是良好的π-受体，并与高 s 特征形成σ键。
