Tantalum(iv) pyrazolate: new wine in the old wineskin

Homoleptic binuclear Ta(iv) pyrazolate [Ta₂(pz)₈] with Ta–Ta distance of 3.1895(7) Å was obtained in a reaction of Ta(NMe₂)₅ with unsubstituted pyrazole Hpz.

A Sterically Hindered Derivative of 2,1,3-Benzotelluradiazole: A Way to the First Structurally Characterised Monomeric Tellurium-Nitrogen Radical Anion

Interaction of the tetradentate redox-active 6,6'-[1,2-phenylenebis(azanediyl)]bis(2,4-di-tert-butylphenol) (H₄ L) with TeCl₄ leads to neutral diamagnetic compound TeL (1) in high yield. The molecule of 1 has a nearly planar TeN₂ O₂ fragment, which suggests the formulation of 1 as Te^II L^2- , in agreement with the results of DFT calculations and QTAIM and NBO analyses. Reduction of 1 with one equivalent of [CoCp₂ ] leads to quantitative formation of the paramagnetic salt [CoCp₂ ]⁺ [1]^.- , which was characterised by single-crystal XRD. The solution EPR spectrum of [CoCp₂ ]⁺ [1]^.- at room temperature features a quintet due to splitting on two equivalent ¹⁴ N nuclei. Below 150 K it turns into a broad singlet line with two weak satellites due to the splitting on the ¹²⁵ Te nucleus. Two-component relativistic DFT calculations perfectly reproduce the a(¹⁴ N) HFI constants and A_∥ (¹²⁵ Te) value responsible for the low-temperature satellite splitting. Calculations predict that the additional electron in 1^.- is localised mainly on L, while the spin density is delocalised over the whole molecule with significant localisation on the Te atom (≥30 %). All these data suggest that 1^.- can be regarded as the first example of a structurally characterised monomeric tellurium-nitrogen radical anion.

The first heterocubane cluster with a [W3GaS4] core

The paramagnetic cuboidal clusters [Mo₃(GaCl)(μ₃-S)₄(dppe)₃Cl₃] and [W₃(GaBr)_0.81(μ₃-S)₄(dppe)₃Br₃] were synthesized by treatment of the corresponding triangular clusters [M₃S₄(dppe)₃X₃]X with [Ga(η⁵-C₅Me₅)]₆.