Schuhknecht Danny, Spaniol Thomas P, Yang Yan, Maron Laurent, Okuda Jun
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany.
CNRS, INSA, UPS, UMR 5215, LPCNO, Université de Toulouse, 135 avenue de Rangueil, 31077 Toulouse, France.
Inorg Chem. 2020 Jul 6;59(13):9406-9415. doi: 10.1021/acs.inorgchem.0c01289. Epub 2020 Jun 16.
The hydride ligand in the cationic calcium hydride supported by a NNNN-type macrocycle, [(MeTACD)Ca(μ-H)(THF)][BAr] (; MeTACD = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane; THF = tetrahydrofuran; BAr = B(CH-3,5-Me)), shows, in addition to its Brönsted basicity toward weak acids, a pronounced nucleophilicity resulting in nucleophilic substitution or insertion (addition) at a silicon or sp carbon center. Terminal acetylenes RC≡CH (R = SiMe, cyclopropyl) as well as 1,4-diphenylbutadiene were deprotonated by to give dinuclear complexes [(MeTACD)Ca(μ-C≡CR)][BAr] (, R = SiMe; , R = cyclopropyl) and [(MeTACD)Ca(μ-η-1,4-PhCH)][BAr] () with H evolution. The addition reaction with BH(THF) gave a tetrahydridoborate complex, [(MeTACD)Ca(BH)(THF)][BAr] (), with κ-HBH coordination in the solid state, suggesting a pronounced Lewis acidic calcium center. The behavior resulting from both Lewis acidity and hydricity becomes apparent in the nucleophilic substitution of fluorobenzene by to give benzene and the dimeric fluoride complex [(MeTACD)Ca(μ-F)(THF)][BAr]·2.5THF (). Analogous nucleophilic substitution reaction is observed for heterofunctionalized organosilanes XSiR [X = I, N(SiHMe), N; R = Me or HMe], which resulted in the formation of calcium complexes [(MeTACD)Ca(X)(THF)][BAr] (-) containing an X ligand along with hydrosilane HSiR. An insertion reaction by was observed with CO and CO to give dinuclear formato complex [(MeTACD)Ca(μ-OCHO)][BAr] () and -enediolato complex [(MeTACD)Ca(μ-OCH═CHO)][BAr]·3.5THF (), respectively. The latter is believed to have been formed as a result of the dimerization of an initially generated formyl or oxymethylene complex, [(MeTACD)Ca(OCH)].
由NNNN型大环支撑的阳离子氢化钙中的氢化物配体，[(MeTACD)Ca(μ-H)(THF)][BAr]（；MeTACD = 1,4,7,10-四甲基-1,4,7,10-四氮杂环十二烷；THF = 四氢呋喃；BAr = B(CH-3,5-Me)），除了对弱酸具有布朗斯特碱性外，还表现出明显的亲核性，导致在硅或sp碳中心发生亲核取代或插入（加成）反应。末端乙炔RC≡CH（R = SiMe、环丙基）以及1,4-二苯基丁二烯被 去质子化，生成双核配合物[(MeTACD)Ca(μ-C≡CR)][BAr]（，R = SiMe；，R = 环丙基）和[(MeTACD)Ca(μ-η-1,4-PhCH)][BAr]（）并放出氢气。与BH(THF)的加成反应生成了一个四氢硼酸根配合物，[(MeTACD)Ca(BH)(THF)][BAr]（），在固态中具有κ-HBH配位，表明钙中心具有明显的路易斯酸性。路易斯酸性和氢性共同导致的行为在 对氟苯的亲核取代反应中表现明显，生成苯和二聚体氟化物配合物[(MeTACD)Ca(μ-F)(THF)][BAr]·2.5THF（）。对于杂功能化有机硅烷XSiR [X = I、N(SiHMe)、N；R = Me或HMe]也观察到了类似的亲核取代反应，反应生成了含有X配体以及硅烷HSiR的钙配合物[(MeTACD)Ca(X)(THF)][BAr]（-）。观察到 与CO和CO发生插入反应，分别生成双核甲酸盐配合物[(MeTACD)Ca(μ-OCHO)][BAr]（）和 -烯二醇盐配合物[(MeTACD)Ca(μ-OCH═CHO)][BAr]·3.5THF（）。据信后者是由最初生成的甲酰基或甲醛亚甲基配合物[(MeTACD)Ca(OCH)]二聚而成。
