Dange Deepak, Gair Andrew R, Jones Dafydd D L, Juckel Martin, Aldridge Simon, Jones Cameron
School of Chemistry , Monash University , PO Box 23 , VIC , 3800 , Australia.
Inorganic Chemistry Laboratory , Department of Chemistry , University of Oxford , South Parks Road , Oxford , OX1 3QR , UK . Email:
Chem Sci. 2019 Feb 4;10(11):3208-3216. doi: 10.1039/c9sc00200f. eCollection 2019 Mar 21.
Reactions of three magnesium(i) dimers, [{(Nacnac)Mg-}] (Nacnac = [(ArNCMe)CH]; Ar = xylyl (Xyl), mesityl (Mes) or 2,6-diethylphenyl (Dep)), with either 1,1-diphenylethylene (DPE), α-methylstyrene (MS), -stilbene (TS) or diphenylacetylene (DPA) led to the 1,2-addition of the Mg-Mg bond across the substrate, giving rise to the 1,2-dimagnesioethanes, [{(Nacnac)Mg}(μ-DPE)], [{(Nacnac)Mg}(μ-MS)], [{(Nacnac)Mg}(μ-TS)] (Ar = Mes or Dep); and a 1,2-dimagnesioethene, [{(Nacnac)Mg}(μ-DPA)]. The reactions involving the 1,1-substituted alkenes are shown to be readily redox reversible, in that the reaction products are in equilibrium with a significant proportion of the starting materials at room temperature. Variable temperature NMR spectroscopy and a van't Hoff analysis point to low kinetic barriers to these weakly exergonic reactions. [{(Nacnac)Mg}(μ-DPE)] and [{(Nacnac)Mg}(μ-DPA)] behave as 1,2-di-Grignard reagents in their reactions with very bulky amido-zinc bromides, yielding the first examples of a 1,2-dizincioethane, [(LZn)(μ-DPE)] (L = -N(Ar*)(SiPr ); Ar* = CHMe{C(H)Ph}-4,2,6), and a 1,2-dizincioethene, [(LZn)(μ-DPA)] (L = -N(SiMe){B(DipNCH)}, Dip = 2,6-diisopropylphenyl), respectively. Divergent reactivity is shown for [{(Nacnac)Mg}(μ-DPE)], which behaves as a two-electron reducing agent when treated with amido-cadmium and amido-magnesium halide precursors, yielding the cadmium(i) and magnesium(i) dimers, [LCdCdL] (L = -N(SiPh){B(DipNCH)}) and [LMgMgL] (L = -N(Ar)(SiMe); Ar = CHPr{C(H)Ph}-4,2,6), respectively. A further class of reactivity for [{(Nacnac)Mg}(μ-DPE)] derives from its reaction with the bulky amido-germanium chloride, LGeCl, which gives a magnesio-germane, presumably intramolecular C-H activation of a highly reactive magnesiogermylene intermediate, [:Ge(L){Mg(Nacnac)}]. [{(Nacnac)Mg}(μ-DPE)] can be considered as acting as a two-electron reducing, magnesium transfer reagent in this reaction.
三种二价镁配合物[{(Nacnac)Mg-}]（Nacnac = [(ArNCMe)CH]；Ar = 二甲苯基（Xyl）、均三甲苯基（Mes）或2,6 - 二乙苯基（Dep））与1,1 - 二苯乙烯（DPE）、α - 甲基苯乙烯（MS）、反式 - stilbene（TS）或二苯乙炔（DPA）反应，使Mg - Mg键在底物上进行1,2 - 加成，生成1,2 - 二镁乙烷[{(Nacnac)Mg}(μ - DPE)]、[{(Nacnac)Mg}(μ - MS)]、[{(Nacnac)Mg}(μ - TS)]（Ar = Mes或Dep）；以及1,2 - 二镁乙烯[{(Nacnac)Mg}(μ - DPA)]。涉及1,1 - 取代烯烃的反应显示出易于氧化还原可逆，因为反应产物在室温下与相当比例的起始原料处于平衡状态。变温核磁共振光谱和范特霍夫分析表明这些弱放能反应的动力学障碍较低。[{(Nacnac)Mg}(μ - DPE)]和[{(Nacnac)Mg}(μ - DPA)]在与非常庞大的酰胺基溴化锌反应时表现为1,2 - 二格氏试剂，分别生成1,2 - 二锌乙烷[(LZn)(μ - DPE)]（L = -N(Ar*)(SiPr)；Ar* = CHMe{C(H)Ph}-4,2,6）和1,2 - 二锌乙烯[(LZn)(μ - DPA)]（L = -N(SiMe){B(DipNCH)}，Dip = 2,6 - 二异丙基苯基）的首例。[{(Nacnac)Mg}(μ - DPE)]表现出不同的反应性，当用酰胺基镉和酰胺基卤化镁前体处理时，它作为双电子还原剂，分别生成镉（I）和镁（I）二聚体[LCdCdL]（L = -N(SiPh){B(DipNCH)}）和[LMgMgL]（L = -N(Ar)(SiMe)；Ar = CHPr{C(H)Ph}-4,2,6）。[{(Nacnac)Mg}(μ - DPE)]的另一类反应性源于其与庞大的酰胺基锗氯化物LGeCl的反应，生成镁锗烷，可能是通过高活性镁锗烯中间体[:Ge(L){Mg(Nacnac)}]的分子内C - H活化。在该反应中，[{(Nacnac)Mg}(μ - DPE)]可被视为一种双电子还原、镁转移试剂。
