Spectroscopic and electrochemical characterization of a Pr⁴⁺ imidophosphorane complex and the redox chemistry of Nd³⁺ and Dy³⁺ complexes

Abstract

The molecular tetravalent oxidation state for praseodymium is observed in solution via oxidation of the anionic trivalent precursor [K][Pr3+(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (1-Pr(NP*)) with AgI at -35 C. The Pr4+ complex is characterized...

Lanthanide Complexes Containing a Terminal Ln═O Oxo Bond: Revealing Higher Stability of Tetravalent Praseodymium versus Terbium

“…25,26 Even when measured oxidation potentials for Tb III and Pr III complexes are nominally equivalent (−0.72 V versus Fc/Fc + ), like in La Pierre and co-workers' [Ln III (NP(1,2,-bis-t Bu-diamidoethane)-(NEt 2 )) 4 ] − complexes, the Pr IV complex evades isolation and is unstable at room temperature in contrast to the Tb IV analogue. 27,31 Lucena et al previously reported on reactions of the LnO 2+ complexes studied in the present work, there with H 2 O to yield LnOH 2+ . In that work it was found that TbO 2+ reacted very inefficiently, with PrO 2+ reacting even slower, at a barely detectable rate.…”

“…Standard electrode potentials, properties of solid materials, solution electrochemistry, and isolable molecular complexes all point to a (slightly) greater stability of Tb IV versus Pr IV . ,,− ,− For example, predicted E 0 (IV/III) for Tb are 0.1–0.4 V less positive than for Pr; and under highly alkaline and concentrated solutions of weak-field complexing ligands, Tb 4+ has a reduction potential of +1.3 V compared to +1.4 V for Pr 4+ . ,, Solid PrF 4 decomposes to PrF 3 at 363 K, whereas TbF 4 is stable to at least 623 K. ,, Mazzanti and co-workers recently isolated [Ln IV (OSiPh 3 ) 4 (MeCN) 2 ] for Ln = Pr and Tb, reporting that the Pr IV complex was reduced at a substantially more positive potential (−0.38 V versus Fc/Fc + ) than the Tb IV complex (−0.96 V versus Fc/Fc + ), indicating higher stability of Tb IV versus Pr IV . , Even when measured oxidation potentials for Tb III and Pr III complexes are nominally equivalent (−0.72 V versus Fc/Fc + ), like in La Pierre and co-workers’ [Ln III (NP­(1,2,-bis- t Bu-diamidoethane)­(NEt 2 )) 4 ] − complexes, the Pr IV complex evades isolation and is unstable at room temperature in contrast to the Tb IV analogue. , …”

“…Significant progress has been made toward synthesizing complexes featuring lanthanide–ligand multiple bonds to terminal carbene, imido, and oxo groups. − Tetravalent lanthanides, Ln IV , are a suitable target for multiple bonding because this relatively high oxidation state lowers the lanthanide orbital energies and facilitates a better energy match with ligand orbitals. − While Ce IV complexes have a comparatively long history, the first reports of isolable complexes featuring Pr IV and Tb IV emerged only in 2019. − To date, no molecular complexes of Pr IV and Tb IV featuring metal–ligand multiple bonds have been isolated.…”

Elucidation of LMCT Excited States for Lanthanoid Complexes: A Theoretical and Solid-State Experimental Framework

“…However, the modeling of a transition to a LMCT state has remained a significant challenge because it requires an accurate description of both the ground state, which is usually a magnetic level and the LMCT excited state, which involves a change of (oxidation) state for the metal and one or more ligands. For this reason, while several multireference ab initio studies of 4f–4f excitations in lanthanoid complexes ,− and 4f–5d transitions in doped glasses − have been reported, ab initio studies of LMCT remain scarce in the literature due to their complexity. , This work sets a foundational framework based on both theoretical and solid-state experimental approaches to investigate LMCT excited states for lanthanoid complexes.…”

“…For this reason, while several multireference ab initio studies of 4f−4f excitations in lanthanoid complexes 25,38−45 and 4f−5d transitions in doped glasses 46−48 have been reported, ab initio studies of LMCT remain scarce in the literature due to their complexity. 49,50 This work sets a foundational framework based on both theoretical and solidstate experimental approaches to investigate LMCT excited states for lanthanoid complexes.…”