Carbonyl Bond Cleavage by Complementary Active Sites

Abstract

We have studied the size-selective reactivity of Al n − clusters with formaldehyde to determine if carbonyl bonds may be broken by complementary active sites. Gas phase experiments reveal that Al n − , where n = 8−12, react with formaldehyde to form Al n−2 CH 2 − , which demonstrates that the carbonyl bond is broken in the reaction with the cluster, while Al 13 − is found to be resistant to reaction. The most likely leaving group is determined to be Al 2 O. We also found n = 15−19 to be reactive with the products being a mix of Al n−2 CH 2 − and Al n (OCH 2 ) m − . Theoretical investigations find that the adjacent Lewis acid and Lewis base sites stabilize the resonance structure in which the carbonyl is reduced to a single bond which encourages carbonyl cleavage. A transition state analysis of the cleavage of the carbonyl bond confirms the size selective cleavage of the carbonyl bond and supports the importance of complementary Lewis acid−Lewis base active sites in governing the reactivity.

Study of the electronic structure, stability and magnetic quenching of CrGen(n = 1–17) clusters: a density functional investigation

“…To nd out the contribution from Cr in the MOs we have used a fragment analysis where clusters are divided into Cr and Ge 12 fragments. 35,43 Using this analysis we found a reasonable amount of contribution from the Cr-3d z 2 atomic orbital in the LUMO which is being pushed up from the lower level. This also could be the reason for the good amount of HOMO-LUMO gap of 0.82 eV in this cluster.…”

The effect of sulfur covalent bonding on the electronic shells of silver clusters

“…A fragmentation analysis as implemented within ADF was performed to get a deeper insight into the nature of the bonding. [58][59][60] In this analysis the system in question is considered as a sum of "fragments," each fragment yielding a basis set. The fragments are then combined to calculate the electronic structure of the full system.…”

Electronic structure, stability, and oxidation of boron-magnesium clusters and cluster solids

“…41 We are particularly interested in clusters that are energetically stable but are also resistant to oxidation. 30,[42][43][44][45] In this regard, we are looking for clusters with a large gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). This is because the ground state of an O 2 molecule is a spin triplet where the majority spin states have a pair of unpaired electrons while the minority states are unfilled.…”