Comparison of zinc and magnesium clusters in their reaction with organochlorides: Toward a molecular picture of grignard reagent formation

• Published in: International journal of quantum chemistry 2012-09, Vol.112 (18), p.3002-3007
• Main Authors: Barsukov, Yu. V., Porsev, V. V., Tulub, A. V.
• Format: Article
• Language: English
• Subjects: B3PW91; Grignard reagent formation; magnesium cluster; radicals; zinc cluster
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/qua.24187

The reaction channels of Znn and Mgn clusters (n = 4, 10) with RCl organochlorides are compared to the investigation of relative activity of metals in the reaction of Grignard reagent formation within a framework of quantum chemical modeling of a reaction path. R radicals are chosen from a list of alkyl (CH3, C2H5, i‐C3H7, and t‐C4H9) and residues with π‐bond (C2H3 and C6H5). Quantum chemistry calculations are made using the density function theory (DFT) approach at the B3PW91/6‐311+G(d) level. The reaction channels for both zinc and magnesium can be classified as radical and nonradical according to the nature of reaction products. The calculation of activation energies shows much similarity in their dependence on the nature of R radical but in the case of zinc, barriers are significantly higher. Both for zinc and magnesium clusters, the radical channels are more preferable in the case of alkyl residues, for vinyl and phenyl residues barriers of radical and nonradical channels are comparable. © 2012 Wiley Periodicals, Inc. Vertical attack of zinc and magnesium clusters by RCl leads to formation of free radicals though the lowest barriers compared to other found reaction channels. High activation energy and high heat of reaction in the case of zinc clusters explain known low activity of zinc metal compared to magnesium metal in their interaction with RCl organohalides.