Peddarao Thota, Sarkar Nabin, Nembenna Sharanappa
School of Chemical Sciences, National Institute of Science Education and Research (NISER), Homi Bhabha National Institute (HBNI), Bhubaneswar 752 050, India.
Inorg Chem. 2020 Apr 6;59(7):4693-4702. doi: 10.1021/acs.inorgchem.9b03778. Epub 2020 Mar 11.
Tetra-aryl-substituted symmetrical conjugated bis-guanidine (CBG) ligands such as L (3H) [L(3H) = {(ArHN)(ArHN)C═N-C═NAr(NHAr)}; Ar = 2,6-Me-CH (L(3H)), 2,6-Et-CH (L(3H)), and 2,6-Pr-CH (L(3H))] have been employed to synthesize a series of four- and six-membered aluminum heterocycles (-) for the first time. Generally, aluminum complexes bearing ,'- chelated guanidinate and β-diketiminate/dipyrromethene ligand systems form four- and six-membered heterocycles, respectively. However, the conjugated bis-guanidine ligand has the capability of forming both four- and six-membered heterocycles possessing multimetal centers within the same molecule; this is due to the presence of three acidic protons, which can be easily deprotonated (at least two protons) upon treatment with metal reagents. Both mono- and dinuclear aluminum alkyls and mononuclear aluminum alkoxide, halide, and hydride complexes have been structurally characterized. Further, we have demonstrated the potential of mononuclear, six-membered CBG aluminum dialkyls in catalytic hydroboration of a broad range of aldehydes and ketones with pinacolborane (HBpin).
首次使用四芳基取代的对称共轭双胍（CBG）配体，如L(3H) [L(3H) = {(ArHN)(ArHN)C═N-C═NAr(NHAr)}；Ar = 2,6-Me-CH（L(3H)）、2,6-Et-CH（L(3H)）和2,6-Pr-CH（L(3H)）] 合成了一系列四元和六元铝杂环化合物（-）。一般来说，带有,'-螯合胍基和β-二酮亚胺/二吡咯亚甲基配体体系的铝配合物分别形成四元和六元杂环。然而，共轭双胍配体能够在同一分子内形成具有多金属中心的四元和六元杂环；这是由于存在三个酸性质子，在用金属试剂处理时它们很容易去质子化（至少两个质子）。单核和双核烷基铝以及单核醇盐、卤化物和氢化物铝配合物均已通过结构表征。此外，我们已经证明了单核六元CBG二烷基铝在催化多种醛和酮与频哪醇硼烷（HBpin）的硼氢化反应中的潜力。
