New Rare Earth Metal Complexes with Nitrogen-Rich Ligands: 5,5′-Bitetrazolate and 1,3-Bis(tetrazol-5-yl)triazenate—On the Borderline between Coordination and the Formation of Salt-Like Compounds

Triple Inverse Sandwich versus End-On Diazenido: Bonding Motifs across a Series of Rhenium-Lanthanide and -Actinide Complexes

While synthesizing a series of rhenium-lanthanide triple inverse sandwich complexes, we unexpectedly uncovered evidence for rare examples of end-on lanthanide dinitrogen coordination for certain heavy lanthanide elements as well as for uranium. We begin our report with the synthesis and characterization of a series of trirhenium triple inverse sandwich complexes with the early lanthanides, Ln[(μ-η5:η5-Cp)Re(BDI)]3(THF) (1-Ln, Ln = La, Ce, Pr, Nd, Sm; Cp = cyclopentadienide, BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate). However, as we moved across the lanthanide series, we ran into an unexpected result for gadolinium in which we structurally characterized two products for gadolinium, namely, 1-Gd (analogous to 1-Ln) and a diazenido dirhenium double inverse sandwich complex Gd[(μ-η1:η1-N2)Re(η5-Cp)(BDI)][(μ-η5:η5-Cp)Re(BDI)]2(THF)2 (2-Gd). Evidence for analogues of 2-Gd was spectroscopically observed for other heavy lanthanides (2-Ln, Ln = Tb, Dy, Er), and, in the case of 2-Er, structurally authenticated. These complexes represent the first observed examples of heterobimetallic end-on lanthanide dinitrogen coordination. Density functional theory (DFT) calculations were utilized to probe relevant bonding interactions and reveal energetic differences between both the experimental and putative 1-Ln and 2-Ln complexes. We also present additional examples of novel end-on heterobimetallic lanthanide and actinide diazenido moieties in the erbium-rhenium complex (η8-COT)Er[(μ-η1:η1-N2)Re(η5-Cp)(BDI)](THF)(Et2O) (3-Er) and uranium-rhenium complex [Na(2.2.2-cryptand)][(η5-C5H4SiMe3)3U(μ-η1:η1-N2)Re(η5-Cp)(BDI)] (4-U). Finally, we expand the scope of rhenium inverse sandwich coordination by synthesizing divalent double inverse sandwich complex Yb[(μ-η5:η5-Cp)Re(BDI)]2(THF)2 (5-Yb), as well as base-free, homoleptic rhenium-rare earth triple inverse sandwich complex Y[(μ-η5:η5-Cp)Re(BDI)]3 (6-Y).

Lanthanide Complexes of Bis(tetrazolato)amine: A Route to Lanthanide Nitride Foams

Metal nitrides are strong refractory ceramic materials known for applications in the coatings, catalysis, and semiconductor industries. Lanthanide nitrides are difficult to prepare in high purity and often require high temperatures and sophisticated equipment. In this work, we present an approach to the synthesis of high-purity f-element nitrides through the use of simple lanthanide salts and the nitrogen-rich ligand 5,5'-bis(1H-tetrazolyl)amine (H₂BTA) to form lanthanide complexes of 5,5'-bis(tetrazolato)amine (BTA^2-). We have demonstrated that, when dehydrated, these types of complexes undergo a self-sustained combustion reaction under an inert atmosphere to yield nanostructured f-element nitride foams for lanthanum and cerium. The synthesis, characterization, and single-crystal X-ray crystallography of the BTA^2- complexes of lanthanum, cerium, praseodymium, neodymium, and europium are also discussed.

Picomolar Traces of Americium(III) Introduce Drastic Changes in the Structural Chemistry of Terbium(III): A Break in the "Gadolinium Break"

The crystallization of terbium 5,5'-azobis[1H-tetrazol-1-ide] (ZT) in the presence of trace amounts (ca. 50 Bq, ca. 1.6 pmol) of americium results in 1) the accumulation of the americium tracer in the crystalline solid and 2) a material that adopts a different crystal structure to that formed in the absence of americium. Americium-doped [Tb(Am)(H₂ O)₇ ZT]₂ ZT⋅10 H₂ O is isostructural to light lanthanide (Ce-Gd) 5,5'-azobis[1H-tetrazol-1-ide] compounds, rather than to the heavy lanthanide (Tb-Lu) 5,5'-azobis[1H-tetrazol-1-ide] (e.g., [Tb(H₂ O)₈ ]₂ ZT₃ ⋅6 H₂ O) derivatives. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter lanthanides, despite a 10⁸ -fold Tb excess. The americium-doped material was studied by single-crystal X-ray diffraction, vibrational spectroscopy, radiochemical neutron activation analysis, and scanning electron microcopy. In addition, the inclusion properties of terbium 5,5'-azobis[1H-tetrazol-1-ide] towards americium were quantified, and a model for the crystallization process is proposed.

New lithium borates with bistetrazolato2- and pyrazinediolato2- ligands - potentially interesting lithium electrolyte additives

We present a convenient synthesis of the first silylated bistetrazole via a catalyzed twin [2 + 3] cycloaddition of TMS-azide at cyanogen and its application to access bistetrazolatoborates, structurally characterized by a unique unsaturated ten-membered B₂N₄C₄ heterocyclic system. Furthermore, new borate anions with two pyrazine-2,3-diolato ligands were synthesized from tetrafluoroborate salts and structurally characterized. Their organic cation can be exchanged for Li⁺via cation exchange. The conceptual relation of these new salts to lithium ion battery bisoxalalatoborate additive LiBOB, a prominent solid electrolyte interface (SEI) generator, is discussed.

Complexes and salts of the nitrogen-rich triazole–tetrazole hybrid ligand with alkali and alkaline earth metal cations: experimental and theoretical findings

A series of the triazole–tetrazole based compounds with Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺ and Ba²⁺ was obtained and fully characterised.

Pentazadiene: a high-nitrogen linkage in energetic materials

The N₅-linear energetic moiety of pentazadiene, a new high-nitrogen linkage in energetic materials, has been constructed for the first time from a triazene precursor.

Synthesis, structure and characterization of neutral coordination polymers of 5,5′-bistetrazole with copper(ii), zinc(ii) and cadmium(ii): a new route to reconcile oxygen balance and nitrogen content of high-energy MOFs

Cu(ii)/Zn(ii)/Cd(ii) coordinated with 5,5′-bistetrazole (H₂BT) formed three novel energetic coordination polymers: [CuBT(H₂O)]_n (1), [ZnBT(H₂O)₂]_n (2) and [CdBT(H₂O)₂]_n (3).