Isomeric Al2R4, Mg2R2 Species and Oligomerisation Products: Investigation of Al–Al and Mg–Mg σ Bonding

✍ Scribed by Tobias Pankewitz; Wim Klopper; Patrick Henke; Hansgeorg Schnöckel

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 877 KB
• Volume: 2008
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200800626

✦ Synopsis

Abstract

Initiated by ongoing experimental work in the field of subvalent aluminium compounds and by recent results on isoelectronic Mg~2~R~2~ (s^1^ states) species, detailed theoretical work was necessary to explain the unusual bonding situation in some Al~2~R~4~ isomers (R = P__t__Bu~2~), of a dimeric Al~4~R′~8~ (R′ = O__t__Bu) as well as of subhalides Al~2~F~4~, Al~2~Cl~4~, Mg~2~Cl~2~ and some of their oligomers. These results are presented in this contribution. Especially the different isomers of the four‐membered heterocyclic RAlR~2~AlR molecule needed careful theoretical investigation, since on the way from monomeric AlR~2~ radicals to the most stable RAlR~2~AlR isomer with a butterfly shape, intermediates with different Al–Al interactions – exhibiting diradical as well as diradicaloid character – have to be considered. The presented results on the unusual bonding in these AlP~2~Al four‐membered heterocyclic systems are an important contribution to a better understanding of the bonding situations in many inorganic molecules containing, for example, B~2~P~2~, C~2~P~2~, Ge~2~N~2~, Sn~2~N~2~ and Si~4~ entities, which recently have drawn considerable interest. In analogy to the Al^II^ compounds some isoelectronic Mg^I^ species have been investigated. Regarding the obtained results, special attention is drawn to MgCl oligomers, since we found unexpectedly high oligomerisation energies in our calculations. This high stabilisation is based on direct Mg–Mg bonding as well as on Mg–Cl–Mg bridging bonds. These mixed bonding motifs may also be present in the so far unknown solid MgCl. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)