Density-Functional Study on the Structures, Stabilities, and Dissociation Pathways of Sc3+(DMSO)n Complexes (n = 1−6)

Abstract

A comprehensive theoretical study is performed on Sc 3 + (DMSO) n complexes up to n = 6 at the B3LYP/6-311+G(d, p) level to understand their structures and stabilities with respect to various dissociation channels, including the evaporation of neutral DMSO, the dissociative electron and proton transfer, the cleavage of a methyl radical (CH 3 ) and methane (CH 4 ) as well as their combined loss (2CH 3 , 2CH 4 , and CH 3 + CH 4 ). The most stable structures of Sc 3 + (DMSO) n correspond to highly symmetric and quasi-spherical configurations. The calculated dissociation energies indicate that the Sc 3 + (DMSO) n species are thermodynamically stable with respect to all considered dissociation processes without charge separation for any size and to the charge-separating processes (dissociative electron transfer and loss of CH 3 +) for n ≥ 4 but are thermodynamically unstable with respect to these charge-separating processes for n = 1-3. The transition states for the charge-separating processes of Sc 3 + (DMSO) n with n = 1-3 are determined, and the calculated energy barriers are found to be high enough to stabilize the respective complex. Therefore, these small species are kinetically metastable with long lifetimes and should be observable. The minimum number (n m i n ) of DMSO ligands required to stabilize the Sc 3 + ion against dissociative electron or proton transfer emerges from our calculations as n m i n = 1, and the critical size (n c r i t ), above which the evaporation of a neutral ligand becomes more favorable than the dissociative electron or proton transfer, is estimated to be n c r i t = 5-6.