Synthesis of a Boronic Acid Anhydride Based Ligand and Its Application in Beryllium Coordination

The synthesis of a boronic acid anhydride-based ligand containing one three- and one four-coordinated boron atom is presented. This ligand was successfully employed as a tridentate κ¹N,κ²O-ligand in the coordination of beryllium chloride and both the ligand and the resulting complex have been structurally characterized. While the boron-element separations are within the typical range of related homo-nuclear compounds, the corresponding beryllium-element distances are rather long, suggesting unexpectedly high electron density at the beryllium center. Incorporation of a beryllium atom in a six-membered ring causes no more distortion than the corresponding boron atom, suggesting that analogous ligand systems could be used in boron and beryllium coordination chemistry. The generated hetero-tri-nuclear complex enables the direct comparison of bond lengths and angles at beryllium and boron atoms in similar coordination environments and can act as a monomolecular model for beryllium borates.