Multiply Borylated Arenes: X‐ray Crystal Structure Analyses and Quantum Chemical Calculations

Abstract

Optimised synthesis procedures and results of X-ray single crystal structure analyses for 4-(dibromoboryl)toluene, 1,3bis(dibromoboryl)benzene, 1,4-bis(dibromoboryl)benzene, and 1,3,5-tris(dibromoboryl)benzene are reported. These compounds have also been studied by Hartree-Fock (HF), density functional theory (DFT), and Møller-Plesset second-order perturbation (MP2) methods in combination with the polarized double-ζ valence (SVP) and polarized triple-ζ valence (TZVP) basis sets of Ahlrichs and coworkers. A comparison of the quantum chemical results for optimised geometries and computed NMR chemical shifts with experiment is presented to test the quality of the various methods Mehrfach borylierte Arene: Kristallstrukturanalysen and quantenchemische RechnungenInhaltsübersicht. Wir berichten über optimierte Synthesevorschriften und die Ergebnisse der Kristallstrukturanalysen von 4-(Dibromoboryl)toluol, 1,3-Bis(dibromoboryl)benzol, 1,4-Bis(dibromoboryl)benzol und 1,3,5-Tris(dibromoboryl)benzol. Diese Verbindungen wurden weiterhin mittels Hartree-Fock (HF), Dichtefunktionaltheorie (DFT) und Møller-Plesset-Störungstheorie (MP2) in Kombination mit dem polarisierten Double-ζ Valenz-(SVP) und dem polarisierten Triple-ζ Valenzbasissatz (TZVP) von Ahlrichs et al. untersucht. Ein Vergleich der optimierten Geometrien und berechneten NMR-Verschiebungen mit den entsprechenden experimentellen Daten dient als Test für die Qualität der unterschiedli-

A Quest for Ligand‐Unsupported Li+–π Interactions in Mono‐, Di‐, and Tritopic Lithium Arylborates

“…Reagents purchased from commercial sources were used as received unless otherwise noted. 1,3,5-Tris(dibromoboryl)benzene (9) [37] and 1,3,5-tris(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-benzene (11) [47,48] were prepared according to previously reported procedures.…”

“…The dilithium salt Li 2 [2] is readily accessible from p-bis(dibromoboryl)benzene (1) [37] and six equivalents of MeLi in Et 2 O/toluene at -78°C. Despite numerous efforts to grow X-ray quality crystals of Li 2 [2] in the absence of strongly coordinating chelators, we were only able to obtain the 12-crown-4 (12-c-4) adduct [Li (12- [2] and Li 2 [5].…”

“…Li 3 [10] was obtained from 1,3,5-tris(dibromoboryl)benzene [37] and nine equivalents of MeLi in Et 2 O/toluene at low temperature. The 11 B{ 1 H} NMR spectrum of Li 3 [10] is characterized by a resonance at -17.3 ppm, typical of four-coordinate boron centers.…”

Copper Complexes of Mono‐ and Ditopic [(Methylthio)methyl]borates: Missing Links and Linked Systems En Route to Copper Enzyme Models

“…SMe 2 and BBr 3 are commercially available. PhBBr 2, [42,45] p-Me 3 Si-C 6 H 4 -BBr 2, [44,45] and LiCH 2 SMe [43] were synthesized following literature procedures.…”

“…For the synthesis of the heteroditopic scorpionates Li 2 [10] and K 2 [10] , the p-silylated borylbenzene 6 [44,45] was chosen as starting material (Scheme 2). Introduction of the thio-A C H T U N G T R E N N U N G ether substituent by using donor-free LiCH 2 SMe gave the silylated analog (7) of 2.…”