Theoretical Studies of Boron−Water Cluster Ions B⁺(H₂O)n and Aluminum−Water Cluster Ions Al⁺(H₂O)n:  Isomers and Intracluster Reactions

With ab initio molecular orbital calculations, structures of the singly positive charged boron−water clusters B + (H 2 O) n and aluminum−water clusters Al + (H 2 O) n are determined. The insertion reaction products HBOH + (H 2 O) n -1 and HAlOH + (H 2 O) n -1 are also investigated. Structures of the dimer-core clusters [M + (H 2 O) 2 ](H 2 O) n -2 are similar to each other for M = B and Al. In contrast, the stability and structures of [B + (H 2 O)](H 2 O) n -1 and [Al + (H 2 O)](H 2 O) n -1 are quite different. The monomer-core boron clusters [B + (H 2 O)](H 2 O) n -1 do not have stable local minima; the spontaneous proton transfer reaction takes place to form BOH(H 3 O) + (H 2 O) n -2 . In other words, the acid−base reaction takes place in such small clusters. In the larger clusters, the reaction further proceeds and the clusters isomerize to the linear type HBOH + (H 2 O) n -1 . On the other hand, in the clusters [Al + (H 2 O)](H 2 O) n -1, no such reaction takes place. The cis-form hydrated products of the insertion reaction HMOH + (H 2 O) n -1 are more reactive, and the acid−base reaction is seen for both M = B and Al.