Beryllium (II) Chloride Complexes with Phosphoryl Ligands: A DFT Study

Beryllium complexes of the types [BeCl2L2] (L = (Me2N)3P(O) (1), (Me2N)2P(O)F (2), Me2NP(O)F2 (3) and P(O)F3 (4)) have been theoretically studied by means of DFT geometry optimization and NMR chemical shift calculations (B3LYP/6-31G(d)). A good correlation was found between calculated and experimental data for complex 2. On going from complex 1 to 4, the Be-L bond underwent considerable lengthening, while that of Be-Cl was shortened (Be-O: 1.646 in 1 vs. 1.740 A° in 4; Be-Cl: 2.043 in 1 vs. 1.953 A° in 4). In the same way, the Be-O-P bond angle was found to decrease from 135° for 1 to 124° for 4. The trends are in good agreement with the calculated metal-ligand binding energies of complexes 1-4. Interestingly, the structural changes are accompanied by increased 9Be chemical shifts towards higher frequencies as the Me2N groups in the ligand are substituted by fluorine atoms. The results were compared to corresponding complexes with tin (IV) chloride, [SnCl4L2]. The theoretical data showed that the use of the 6-31G* basis set could efficiently predict the 9Be NMR chemical shifts in the complexes [BeCl2L2].

9Be nuclear magnetic resonance spectroscopy trends in discrete complexes: an update

Abstract9Be solution NMR spectroscopy is a useful tool for the characterisation of beryllium complexes. An updated comprehensive table of the 9Be NMR chemical shifts of beryllium complexes in solution is presented. The recent additions span a greater range of chemical shifts than those previously reported, and more overlap is observed between the chemical shift regions of four-coordinate complexes and those with lower coordination numbers. Four-coordinate beryllium species have smaller ω1/2 values than the two- and three-coordinate species due to their higher order symmetry. In contrast to previous studies, no clear relationship is observed between chemical shift and the size and number of chelate rings.

Coordination chemistry of Be2+ ions with chelating oxygen donor ligands: further insights using electrospray mass spectrometry

The electrospray ionisation mass spectrometric (ESI-MS) behaviour of various complexes of beryllium have been investigated in the work described in this paper. These beryllium complexes were analysed in situ on a small scale by preparing appropriate molar mixtures of the Be2+ ion with ligands in a range of solvent systems. In view of the toxicity of beryllium compounds, this combinatorial type screening, involving miniscule amounts of material in solution, proved to be a safe strategy to pursue the coordination chemistry of beryllium. A variety of beryllium complexes were generated with various ligands in solutions and subjected to detailed characterisation by ESI-MS. These ligands, containing functional groups or architecture of interest, varied from simple ligands such as the acetate ion to more common beryllium chelators including hydroxy keto ligands (maltol, tropolone), malonic acid, chromotropic acid and citric acid. Generally, there was excellent correlation between the species observed in the mass spectrum and those confirmed to exist in solution by other techniques. This lent strong credence to the ESI-MS methodology used as an efficient analytical technique for the easy screening of a diverse range of potential ligands for the divalent beryllium ion.

Tuning receptors for the encapsulation of beryllium2+

A method for evaluating second sphere H-bonding interactions as a means to tune specific characteristics in coordinating ligands has been used to evaluate the binding strength of a series of beryllium complexes.