Trivalent Rare-Earth-Metal Bis(trimethylsilyl)amide Halide Complexes by Targeted Oxidations

Abstract

In contrast to previously applied salt metathesis protocols the targeted rare-earth-metal compounds Ln[N(SiMe)](halogenido) were accessed by oxidation of Ln(II) silylamide precursors. Treatment of Sm[N(SiMe)](thf) with 0.5 equiv of CCl or 0.25 equiv of TeBr in thf and crystallization thereof gave [Sm{N(SiMe)}(μ-X)(thf)] (X = Cl, Br). A similar reaction/crystallization procedure performed with 0.5 equiv of 1,2-diiodoethane gave monomeric Sm[N(SiMe)]I(thf). Switching to Yb[N(SiMe)](thf), the aforementioned oxidants generated monomeric five-coordinate complexes Yb[N(SiMe)]X(thf) (X = Cl, Br, I). The reaction of Eu[N(SiMe)](thf) with 0.5 equiv of CCl in thf yielded the separated ion pair [Eu{N(SiMe)}Cl][(thf)Eu(μ-Cl)Eu(thf)]. Performing the chlorination in n-hexane led to oxidation followed by rapid disproportionation into EuCl(thf) and Eu[N(SiMe)]. The bromination reaction did not afford crystalline material, while the iodination gave crystals of divalent EuI(thf). Use of trityl chloride (PhCCl) as the oxidant in thf accomplished the Eu(III) species [Eu{N(SiMe)}(μ-Cl)(thf)]. In situ oxidation of putative [Tm{N(SiMe)}(thf) ] using 0.5 equiv of CCl in thf followed by crystallization from n-hexane led to the formation of a mixture of [Tm{N(SiMe)}(μ-Cl)(thf)] and Tm[N(SiMe)]. Switching the oxidant to 0.5 equiv of 1,2-diiodoethane and crystallizing from thf repeatedly afforded the bis-halogenated complex Tm[N(SiMe)]I(thf).

Heteroleptic samarium(iii) halide complexes probed by fluorescence-detected L3-edge X-ray absorption spectroscopy

“… 50 , 51 Anwander and co-workers have recently shown that ligand redistribution processes are less prevalent when oxidative routes are applied to such species. 9 Therefore, the increased steric bulk of N †† over N′′ allows for the preparation of three-coordinate monomeric heteroleptic complexes with no coordinated solvent, and this bulk also imparts the necessary kinetic stabilisation to circumvent ligand redistribution processes in such unsolvated complexes to allow 2-X to be fully characterised.…”

“…Similar methodologies have recently been applied by Anwander and co-workers to generate Ln( iii ) halide complexes from Ln( ii ) bis(silylamide) precursors. 9 …”

Electronic structures of bent lanthanide(III) complexes with two N-donor ligands

“…Oxidation of the Ln 2+ complexes 1-Ln with either t BuCl (Ln ¼ Sm, 36 Tm) or [FeCp 2 ][PF 6 ] (Yb) in toluene gave the heteroleptic Ln 3+ complexes 3-Ln in good yields (58-72%) following recrystallization from hexane (Scheme 1); similar oxidative procedures on Ln 2+ bis(silyl)amide complexes have recently been applied by Anwander and co-workers. 38 4 ] in benzene (Sm, Tm) or toluene (Yb) yielded the bent Ln 3+ complexes, 2-Ln, in moderate yields (46-70%) aer recrystallization from DCM layered with hexane (Scheme 1). The silylium reagent was selected for its solubility in non-coordinating solvents and for the provision of a large thermodynamic driving force for the reaction.…”

Lewis‐Acid Stabilized Organoimide Complexes of Divalent Samarium, Europium, and Ytterbium

“…The feasibility of such thermally stable divalentl anthanide imides prompted us to further investigate into their redox chemistry.I np revious studies 1e À -oxidation agents, such as halogenating agents, [40] organothallium, [47] or organolead [48,49] compounds have been used for Ln II -to-Ln III conversions. As half-sandwich Ln III imide complexeso ft he type [Cp*Ln(NR)] (Cp* = C 5 Me 5 )p ose attractive targetc ompounds, we were par-ticularlyi nterested in reagents capable of oxidative Cp* ligand transfer.Similar to organothallium(I) compounds, organolead(II) compounds can act as such oxidation and ligand transfer reagents, [47] which is also demonstrated by their redox potentials of Tl I /Tl 0 À0.34 Va nd Pb II /Pb 0 À0.13 V( PbSO 4 /Pb 0 ,S O 4 2À at À0.36 V).…”