Beryllium (II) Chloride Complexes with Phosphoryl Ligands: A DFT Study
K. Essalah
Université Tunis El Manar, Unité de Recherche Modélisation en Sciences Fondamentales et en Didactique, Equipe de Chimie Théorique et Réactivité (UR14ES10), Institut Préparatoire aux Etudes d’Ingénieur d’El Manar B.P 244, Tunis 2092, Tunisia.
M. A. K. Sanhoury *
Laboratory of Coordination Chemistry, Department of Chemistry, Faculty of Sciences of Tunis, University of Tunis El Manar, 1060 Tunis, Tunisia. and Research Unit of Materials Chemistry, Faculty of Sciences and Techniques, UNA, Nouakchott, Mauritania.
M. T. Ben Dhia
Laboratory of Coordination Chemistry, Department of Chemistry, Faculty of Sciences of Tunis, University of Tunis El Manar, 1060 Tunis, Tunisia.
M. R. Khaddar
Laboratory of Coordination Chemistry, Department of Chemistry, Faculty of Sciences of Tunis, University of Tunis El Manar, 1060 Tunis, Tunisia.
*Author to whom correspondence should be addressed.
Abstract
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].
Keywords: Phosphoryl ligand, beryllium (II) chloride, HMPA, shielding constant, 9Be NMR, DFT/B3LYP.