Binding motifs for lanthanide hydrides: a combined experimental and theoretical study of the MH(x)(H2)(y) species (M = La-Gd; x = 1-4; y = 0-6).

The results of a combined spectroscopic and computational study of lanthanide hydrides with the general formula MH(x)(H(2))(y), where M = La, Ce, Pr, Nd, Sm, Eu, and Gd, x = 1-4, and y = 0-6 are reported. To understand the nature of the dihydrogen complexes formed with lanthanide metal hydride molecules, we have first identified the binary MH(x) species formed in the ablation/deposition process and then analyzed the dihydrogen supercomplexes, MH(x)(H(2))(y). Our investigation shows that the trihydrides bind dihydrogen more weakly than the dihydrides and that the interaction between the central lanthanide and the H(2) molecules occurs via a 6s electron transfer from the lanthanide to the H(2) molecules. Evidence is also presented for the SmH and EuH diatomic molecules and the tetrahydride anions in solid hydrogen.