Properties of Lanthanide Hydroxide Molecules Produced in Reactions of Lanthanide Atoms with H₂O₂ and H₂ + O₂ Mixtures: Roles of the +I, +II, +III, and +IV Oxidation States

Abstract

The reactions of laser-ablated lanthanide metal atoms with hydrogen peroxide or hydrogen plus oxygen mixtures have been studied experimentally in a solid argon matrix and theoretically with the ab initio MP2 and CCSD(T) methods. The Ln(OH) and Ln(OH) molecules and Ln(OH) cations are the major products, and the reactions to form those hydroxides are predicted to be highly exothermic at the CCSD(T) level. Vibronic interactions are hypothesized to contribute to the abnormalities in deuterium shifts for Ln-OH(D) stretching modes for several hydroxides, consistent with CASSCF calculations. Additional new absorptions were assigned as HLnO or LnOH and OLnOH molecules. The tetrahydroxides of Ce, Pr, and Tb have also been observed. These reactive intermediates were identified from their matrix infrared spectra by using DO, HD, D, O, and O isotopic substitution, by matching observed frequencies with values calculated by electronic structure methods, and by following the trends observed in frequencies going through different lanthanide metal hydroxide series across the periodic table. The lanthanides are in the +II oxidation state for Ln(OH) and are in the +III oxidation state for Ln(OH) and Ln(OH).

Bond dissociation energies of low-valent lanthanide hydroxides: lower limits from ion–molecule reactions and comparisons with fluorides

“…Dixon and co-workers reported computed energies for reactions that produce LnF and LnOH. 28,65 Although BDEs were not the primary goal of that work, they follow from the reported energies. As all of the computations-from 2011 for fluorides 65 and 2017 for hydroxides 28 -employed a coupled cluster CCSD(T) level of theory using the same basis sets, it is reasonable to compare the results.…”

“…30 The authors of the computational work provided details about their rationale for selection of the particular methods and basis sets. 28,65 For the first half of the All six of these anomalies are in the second half of the lanthanide series, where electron correlation of multiple 4f electrons, and obtaining the correct spin localization and coupling, introduces particular computational challenges. 73,74 Computational limitations such as revealed in Fig.…”

“…Whereas molecular properties such as effective electric field can often be accurately computed, 19,20 computation of BDEs is often complicated by large disparities between electronic structures of bound LnX + versus the constituent fragments Ln + and X. 27,28 Because the formal lanthanide oxidation states are Ln (I) and Ln (II) in LnX and LnX + , respectively, the BDEs reflect relative stabilities of these low valence states towards further reduction. Formation of LnX + can occur by reaction (3), where X-atom donor RX may be an organic (C m H n X), a hydrogen halide (HX), or water in the specific case of reaction (3 0 ).…”

A Density Functional Theory Investigation of the Reaction of Water with Ce2O-

“…In addition, various experimental and theoretical studies have explored the reactivity of classes of cerium-based clusters with various gas-phase small molecules. 17,19,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] Of particular interest here are computational studies conducted by Zhou and co-workers on the reactivity of Ce n (n=1-3) with up to six water molecules. 37,38 Their results indicate high reactivity of these cerium clusters and their efficiency in decomposing multiple water molecules.…”

A Density Functional Theory Investigation of the Reaction of Water with Ce2O-

“…In addition, various experimental and theoretical studies have explored the reactivity of classes of cerium-based clusters with various gas-phase small molecules. 17,19,39,42,[44][45][46][47][48][49][50][51][52][53][54][55][56] Of particular interest here are computational studies conducted by Zhou and co-workers on the reactivity of Ce n (n=1-3) with up to six water molecules. 44,45 Their results indicate high reactivity of these cerium clusters and their efficiency in decomposing multiple water molecules.…”