From Very Strong to Inexistent Be−Be Bonds in the Interactions of Be2 with π‐Systems. Issue 24 (24th November 2020)

• Record Type: Journal Article
• Authors: Vos, Eva; Montero‐Campillo, M. Merced; Corral, Inés; Yáñez, Manuel; Alkorta, Ibon; Elguero, José
• Is Part Of: Chemphyschem. Volume 21:Issue 24(2020)
• Page Start: 2701
• Page End: 2708
• Publication Date: 2020-11-24
• Subjects: ab initio calculations -- Be−Be bonds -- beryllium -- Lewis acids -- pi systems; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202000412
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: Isolated Be2 is a typical example of a weakly bound system, but interaction with other systems may give rise to surprising bonding features. The interactions between Be2 and a set of selected neutral Cn Hn (n=2–8) π‐systems have been analyzed through the use of G4 and G4MP2 ab initio methods, along with multireference CASPT2//CASPT2 calculations. Our results systematically show that the Cn Hn −Be2 −Cn Hn clusters formed are always very stable. However, the nature of this interaction is completely different when the π‐system involved is a closed shell species (n=2, 4, 6, 8), or a radical (n=3, 5, 7). In the first case, the interaction does not occur with the π‐system as a whole, but with specific C centers yielding rather polar but strong C−Be bonds. Nonetheless, although the Be−Be distances in these complexes are similar to the ones in compounds with ultra‐strong Be−Be bonds, a close examination of their electron density distribution reveals that no Be−Be bonds exist. The situation is totally different when the interaction involves two π‐radicals, Cn Hn −Be2 −Cn Hn (n=3, 5, 7). In these cases, a strong Be−Be bond is formed. Indeed, even though Be is electron deficient, the Be2 moiety behaves as an efficient electron donor towards the two π‐radicals, so that the different Cn Hn −Be2 −Cn Hn (n=3, 5, 7) clusters are the result of the interaction between Be2 2+ and two L − anions. The characteristics of these two scenarios do not change when dealing with bicyclic π‐compounds, such as naphthalene and pentalene, because the interaction with the Be2 moiety is localized on one of the unsaturated cycles, the other being almost a spectator. Abstract : Closed shell or radical makes the difference : The interactions between Be2 and a set of selected neutral Cn Hn (n=2–8) π‐systems have been analyzed through the use of G4 and G4MP2 ab initio methods, along with multireference CASPT2//CASPT2 calculations. Complexes between closed‐ and open‐shell π‐systems and Be2 were found to be characterized by rather short Be−Be distances, but only the latter complexes did exhibit Be−Be bonds.