Group 13 Heavier Carbene Analogues Stabilized by the Bulky Bis(4-benzhydryl-benzoxazol-2-yl)methanide Ligand

On the basis of the bulky bis(4-benzhydryl-benzoxazyl-2-yl)methane ligand ((4-BzhH2)Box(2)CH(2)), neutral monovalent group 13 complexes [M-13((4-BzhH2)Box(2)CH)] [M-13 = Tl (1), In (2), or Ga (3)] have been synthesized by salt metathesis reaction of the corresponding potassium or sodium precursor and TlOTf, InOTf, or GaI. The diiodido gallium species [GaI2((4-BzhH2)Box(2)CH)] (3a) was realized as a byproduct once the synthesis of 3 was carried out at higher temperatures. The synthesis of [AlI2((4-BzhH2)Box(2)CH)] (6) as a potential precursor for an aluminum(I) congener was accomplished by two alternative synthetic routes. During one of those procedures, [AlMe2((4-BzhH2)Box(2)CH)] (4) was synthesized in good yields by deprotonation with an AlMe3 solution (method A). Subsequently, 4 was converted to the monoiodinated species [AlMeI((4-BzhH2)Box(2)CH(2))] (5) using 1 equiv of I-2 or to 6 by iodination with 2 equiv of I-2 at 70 degrees C for 4 days. As an alternative, complex 6 could be prepared by iodination of 1 equiv of I-2 and [AlH2((4-BzhH2)Box(2)CH)] (7), which was previously obtained by facile reaction of (4-BzhH2)Box(2)CH(2) and AlH3NMe2Et. All main products 1-7 were completely characterized by nuclear magnetic resonance spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray structure determination. Alane 7 was additionally analyzed by solid-state fluorescence spectroscopy. Density functional theory calculations on [M-13((4-BzhH2)Box(2)CH)] [M-13 = Tl (1), In (2), Ga (3), or Al] revealed that the complexes consist of monovalent group 13 cations coordinated by an anionic ((4-BzhH2)Box(2)CH) ligand similar to metallacycles incorporating a NacNac ligand.

Automated summary

In this study, neutral monovalent group 13 complexes were synthesized using a bulky bis(4-benzhydryl-benzoxazyl-2-yl)methane ligand, with compounds including Tl, In, and Ga. Additionally, a potential precursor for an aluminum(I) congener was successfully synthesized through two alternative synthetic routes. All main products were thoroughly characterized by various analytical techniques, such as nuclear magnetic resonance spectroscopy and single-crystal X-ray structure determination.