Reductions of tetravalent group 4 metal β-diketiminates, [MIVCl3(nacnac)(thf)
n
] (2a, M = Ti; 3b, M
= Zr; 3c, M = Hf; nacnac = {N(Tbt)C(Me)CHC(Me)N(Mes)}-, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl, n = 0, 1), with 2 equiv of KC8 in the presence of LiCl and
tmeda afforded the metal-imido complexes [MNTbt{C(Me)CHC(Me)N(Mes)}(μ-Cl)2Li(tmeda)] (4a,
M = Ti; 4b, M = Zr; 4c, M = Hf; tmeda = Me2NCH2CH2NMe2). The formation of imido complexes
4a−c can be explained in terms of the generation of the corresponding divalent complexes [MIICl(nacnac)(L)
n
] (6a, M = Ti; 6b, M = Zr; 6c, M = Hf; L = thf or Li(tmeda), etc.), followed by the
reductive, regioselective cleavage of the CN bond tethered to the Tbt group. The intermediacy of the
divalent titanium complex 6a was supported by the alternative formation of 4a in the reaction of [Li(nacnac)] (1) with [TiIICl2(tmeda)2]. Interestingly, 4a−c reacted with H2O to give the free ligand nacnacH
(8).
Multidecker organoeuropium sandwich complexes were synthesized with the organic ligands 1,3,5,7-cyclooctatetraene (COT) and 1,4-and 1,6bis(trimethylsilyl)cyclooctatetraenes (COT″) in a liquid ammonia solution of europium (Eu) metal. Infrared (IR) absorption and Raman spectroscopies and magnetic measurements were used to identify local structures and charge distributions. It was found that the organoeuropium complexes have Eu 2+ −COT 2− (Eu 2+ −COT″ 2− ) charge distributions, including a local structure of ligand−Eu− ligand sandwiches. Together with elemental analysis by inductively coupled plasma atomic emission spectroscopy, it is shown that the organoeuropium complexes form a multidecker sandwich structure that is insouble in many solvents. In addition to their paramagnetic behaviors at 150−300 K, the organoeuropium complexes of Eu−COT and Eu−COT″ showed red and orange−red emissions, respectively, under UV irradiation. The introdution of bulky trimethylsilyl groups onto COT prominently enhanced the emission intensity by more than a factor of 10 compared to that of Eu−COT, and similar emission enhancement was observed when ethylenediamine vapor was contacted with Eu−COT solid. The intensity enhancement and the shifts in the emission wavelength are discussed from the viewpoint of orbital interactions between Eu 2+ and COT 2− (COT″ 2− ).
Unique (1-aza-2-butenyl)titanium complexes bearing a phosphonium ylide moiety [Ti=NTbt{C(Me)(PR3)CH=C(Me)N(Mes)}Cl] (3-5, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl) were formed by the nucleophilic attack of PMe3, P(n-Bu)3, and 1,2-bis(dimethylphosphino)ethane (dmpe) toward the corresponding (1-aza-1,3-butadienyl)titanium complex, [Ti=NTbt{C(Me)CHC(Me)N(Mes)}(mu-Cl)2Li(tmeda)] (2a). The reaction of a lithium beta-diketiminate, [Li{N(Tbt)C(Me)CHC(Me)N(Mes)}] (1) with [TiIICl2(dmpe)2] also resulted in the formation of the same complex 5. Density functional theory calculation indicated that the negative charge of the model molecule of 3 was slightly delocalized to the C3N plane. In addition, the calculation of the model molecule of 2a suggested the electrophilicity of 2a at the carbon atom connecting to the titanium atom. Interestingly, the reaction of zirconium and hafnium analogues (2b and 2c) with PMe3 and dmpe did not proceed. In contrast to the cases of phosphine reagents, pyridine which was found to undergo the nucleophilic attack toward the titanium center of 2a gave the pyridine-coordinated titanium-imide [Ti=NTbt{C(Me)CHC(Me)N(Mes)}Cl(py)] (7).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.