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The yttrium gallabenzene complex [(1‐Me‐3,5‐tBu2−C5H3Ga)(μ‐Me)Y(2,4‐dtbp)] is accessible from Y(GaMe4)3 and K(2,4‐dtbp) via a tandem salt metathesis/methane elimination (2,4‐dtbp=2,4‐di‐tert‐butyl‐pentadienyl). The pentadienyl ligand in [(1‐Me‐3,5‐tBu2−C5H3E)(μ‐Me)Y(2,4‐dtbp)] (E=Al, Ga) is easily displaced by salt metathesis with KC5Me5 and KTpMe,Me (TpMe,Me=tris(pyrazolyl‐Me2‐3,5)borato) affording [(1‐Me‐3,5‐tBu2−C5H3E)(μ‐Me)Y(TpMe,Me)] and [(1‐Me‐3,5‐tBu2−C5H3E)(μ‐Me)Y(C5Me5)]. The yttrium center in [(1‐Me‐3,5‐tBu2−C5H3E)(μ‐Me)Y(2,4‐dtbp)] readily forms adducts with neutral Lewis bases like 4‐DMAP (4‐dimethylaminopyridine), PMe3, DMPE (1,2‐bis(dimethylphosphino)ethane), and DME (1,2‐dimethoxyethane). In stark contrast, addition of TMEDA (N,N,N',N'‐tetramethylethylenediamine) results in methyl/pentadienyl exchange between aluminum and yttrium resulting in [(1‐(2,4‐dtbp)‐1‐Me‐3,5‐tBu2−C5H3Al)Y(Me)(tmeda)]. The bonding features of the newly synthesized complexes are analyzed by single‐crystal X‐ray diffraction (SCXRD) and heteronuclear (89Y, 31P) NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Commercially available stock solutions of organolithium reagents are well‐implemented tools in organic and organometallic chemistry. However, such solutions are inherently contaminated with lithium halide salts, which can complicate certain synthesis protocols and purification processes. Here, we report the isolation of chloride‐free methyllithium employing K[N(SiMe3)2] as a halide‐trapping reagent. The influence of distinct LiCl contaminations on the 7Li‐NMR chemical shift is examined and their quantification demonstrated. The structural parameters of new chloride‐free monomeric methyllithium complex [(Me3TACN)LiCH3], ligated by an azacrown ether, are assessed by comparison with a halide‐contaminated variant and monomeric lithium chloride [(Me3TACN)LiCl], further emphasizing the effect of halide impurities. [ABSTRACT FROM AUTHOR]

Kommerziell erhältliche Stammlösungen von Organolithiumverbindungen sind vielfach eingesetzte Reagenzien in der Organischen und Metallorganischen Chemie. Solche Lösungen sind jedoch von "Natur aus" mit Lithiumhalogenidsalzen verunreinigt, die viele Syntheseprotokolle und Aufreinigungsprozesse erheblich einschränken. In dieser Arbeit beschreiben wir die Isolierung von chloridfreiem Methyllithium mithilfe von K[N(SiMe3)2] als Halogenidfällungsreagenz. Der Einfluss von definierten LiCl‐Verunreinigungen auf die 7Li‐NMR chemische Verschiebung wurde systematisch untersucht und quantifiziert. Die strukturellen Parameter des neuen chloridfreien Methyllithiumkomplexes [(Me3TACN)LiCH3] wurden mit der halogenidverunreinigten Variante und monomerem Lithiumchlorid [(Me3TACN)LiCl] verglichen. [ABSTRACT FROM AUTHOR]

CeCl3(thf) reacts at low temperatures with MeLi, t‐BuLi, and n‐BuLi to isolable organocerium complexes. Solvent‐dependent extensive n‐BuLi dissociation is revealed by 7Li NMR spectroscopy, suggesting "Ce(n‐Bu)3(thf)x" or solvent‐separated ion pairs like "[Li(thf)4][Ce(n‐Bu)4(thf)y]" as the dominant species of the Imamoto reagent. The stability of complexes Li3Ln(n‐Bu)6(thf)4 increases markedly with decreasing LnIII size. Closer inspection of the solution behavior of crystalline Li3Lu(n‐Bu)6(thf)4 and mixtures of LuCl3(thf)2/n‐BuLi in THF indicates occurring n‐BuLi dissociation only at molar ratios of <1:3. n‐BuLi‐depleted complex LiLu(n‐Bu)3Cl(tmeda)2 was obtained by treatment of Li2Lu(n‐Bu)5(tmeda)2 with ClSiMe3, at the expense of LiCl incorporation. Imamoto's ketone/tertiary alcohol transformation was examined with 1,3‐diphenylpropan‐2‐one, affording 99 % of alcohol. [ABSTRACT FROM AUTHOR]

CeCl3(thf) reagiert bei niedrigen Temperaturen mit MeLi, t‐BuLi und n‐BuLi zu isolierbaren Organocer‐Komplexen. Eine lösemittelabhängige, z. T. stark ausgeprägte Dissoziation von n‐BuLi konnte durch 7Li‐NMR‐Spektroskopie aufgeklärt werden. Dieses Verhalten deutet darauf hin, dass "Ce(n‐Bu)3(thf)x" oder Solvens‐separierte Ionenpaare wie "[Li(thf)4][Ce(n‐Bu)4(thf)y]" die dominanten Spezies des Imamoto‐Reagenzes sind. Die Stabilität der Komplexe Li3Ln(n‐Bu)6(thf)4 steigt mit der Abnahme der LnIII‐Größe deutlich. Untersuchungen zum Lösungsverhalten von kristallinem Li3Lu(n‐Bu)6(thf)4 und Mischungen von LuCl3(thf)2/n‐BuLi in THF deuten darauf hin, dass eine merkliche Dissoziation von n‐BuLi nur bei Molverhältnissen von <1:3 erfolgt. Der an n‐BuLi abgereicherte Komplex LiLu(n‐Bu)3Cl(tmeda)2 wurde durch Behandlung von Li2Lu(n‐Bu)5(tmeda)2 mit ClSiMe3 gewonnen, jedoch auf Kosten einer Einlagerung von LiCl. Imamotos Transformation von Ketonen zu tertiären Alkoholen wurde mit 1,3‐Diphenylpropan‐2‐on untersucht und lieferte 99 % des Alkohols. [ABSTRACT FROM AUTHOR]

Abstract: The recently reported luminescent chromium(III) complex 13+ ([Cr(ddpd)2]3+; ddpd=N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) shows exceptionally strong near‐IR emission at 775 nm in water under ambient conditions (Φ=11 %) with a microsecond lifetime as the ligand design in 13+ effectively eliminates non‐radiative decay pathways, such as photosubstitution, back‐intersystem crossing, and trigonal twists. In the absence of energy acceptors, such as dioxygen, the remaining decay pathways are energy transfer to high energy solvent and ligand oscillators, namely OH and CH stretching vibrations. Selective deuteration of the solvents and the ddpd ligands probes the efficiency of these oscillators in the excited state deactivation. Addressing these energy‐transfer pathways in the first and second coordination sphere furnishes a record 30 % quantum yield and a 2.3 millisecond lifetime for a metal complex with an earth‐abundant metal ion in solution at room temperature. [ABSTRACT FROM AUTHOR]

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