An Approach to Pin Down the Solid-State Structure of the “Turbo Grignard”

Single crystals of [iPrMgCl­(THF)]2[MgCl2(THF)2]2 were obtained
by layering a
THF solution of the “turbo Grignard” iPrMgCl·LiCl with Et2O at ambient temperature. The
isolated 1:1 Grignard–MgCl2 adduct is isostructural
with crystalline compounds which were obtained from pure RMgCl solutions
(R = Me, tBu, Ph, Bn). The structure of [iPrMgCl­(THF)]2[MgCl2(THF)2]2 reveals an open-cube motif (monoclinic, P21/c). When dioxane was added to a THF
solution of iPrMgCl·LiCl, single crystals of
[LiCl­(THF)2]2 and [iPr2Mg­(dioxane)]∞ (monoclinic, C2/c) were isolated. From 1:1 mixtures of (Me3Si)2CHMgCl (DisylMgCl) and LiCl (prepared analogously
to iPrMgCl·LiCl) two different Grignard compounds,
the monomer [DisylMgCl­(THF)2] (monoclinic, P21) and the dimer [DisylMgCl­(THF)]2 (monoclinic, P21/c), were isolated as single
crystals. During our studies, two oxidation products of iPrMgCl and DisylMgCl, respectively, resulting from oxygen insertion,
were obtained and structurally characterized. Colorless plates of
[iPrMg­(OiPr)]4 (monoclinic, P21/m) grew from a THF/benzene
solution. The dimeric alkoxide {[DisylOMgCl]­[LiCl­(THF)2]}2 (monoclinic, C2/c), which was obtained from DisylMgCl·LiCl by oxidation through
residual oxygen, displays the only structure in which incorporation
of LiCl in the molecular framework of a Mg alkoxide was observed.

在室温条件下，将“涡轮增压型格氏试剂（turbo Grignard）”iPrMgCl·LiCl的四氢呋喃（THF）溶液与乙醚（Et₂O）分层，得到了[iPrMgCl(THF)]₂[MgCl₂(THF)₂]₂的单晶。所分离得到的1:1型格氏试剂-氯化镁加合物，与从纯RMgCl溶液（R=Me、tBu、Ph、Bn）中得到的结晶化合物具有同构性。[iPrMgCl(THF)]₂[MgCl₂(THF)₂]₂的晶体结构呈现开放立方骨架基元，所属晶系为单斜晶系，空间群为P2₁/c。向iPrMgCl·LiCl的四氢呋喃溶液中加入二氧六环（dioxane）后，分离得到了[LiCl(THF)₂]₂和聚合型[iPr₂Mg(dioxane)]_∞的单晶，所属晶系为单斜晶系，空间群为C2/c。将(Me₃Si)₂CHMgCl（DisylMgCl）与氯化锂（LiCl）按1:1比例混合（制备方法与iPrMgCl·LiCl类似），可分离得到两种不同的格氏试剂单晶：单体形态的[DisylMgCl(THF)₂]（单斜晶系，空间群P2₁），以及二聚体形态的[DisylMgCl(THF)]₂（单斜晶系，空间群P2₁/c）。在本研究中，分别通过氧插入反应得到了iPrMgCl与DisylMgCl的两种氧化产物，并对其结构进行了表征。从四氢呋喃/苯（benzene）混合溶液中培养得到了无色片状的[iPrMg(OiPr)]₄单晶，所属晶系为单斜晶系，空间群为P2₁/m。通过残留氧气氧化DisylMgCl·LiCl得到的二聚型醇盐{[DisylOMgCl][LiCl(THF)₂]}₂，所属晶系为单斜晶系，空间群为C2/c，是目前唯一被观测到的氯化锂掺入镁醇盐分子骨架中的晶体结构。