The coordination chemistry of the hydro­tris­[3-(2-furyl)pyrazol-1-yl]borate (Tp^2-Fu) ligand is explored with cerium(III) and dysprosium(III). The difference in Lewis acidity of the ions reveals varying stability in the bis-Tp^2-Fu lan­tha­nide com­plexes.

Three soft scorpionate coordination complexes of alkali metals are presented together with an overview of the structural preferences of alkali metal soft scorpionate complexes. This analysis suggests that these thione-based ligands will continue to be a rich source of inter­esting alkali metal motifs worthy of isolation and characterization.

The synthesis and structure are reported of Tp^Ph,4CNNi(NO₃)(EtOH), an octa­hedral complex containing a tridentate cyano­scorpionate ligand, a bidentate nitrate ligand and a neutral ethanol ligand.

Three N atoms from the facially capping tridentate chelating tris­(4,4-di­methyl­oxazolin-2-yl)phenyl­borate ligand and a chloride ligand coordinate an Ni^II ion in a highly distorted tetra­hedral geometry. The Ni—Cl bond length [2.1851 (5) Å] is comparable to those found in a previously reported tris­(3,5-di­methyl­pyrazol-1-yl)hydro­borate derivative [2.1955 (18) and 2.150 (2) Å]. The mol­ecular structure deviates from C_3v symmetry due to the structural flexibility of the tris­(4,4-di­methyl­oxazolin-2-yl)phenyl­borate ligand.

The metal complex is composed of a central copper(I) atom, distorted tetra­hedrally coordinated by two of the three pyridazine-3-thione rings and the H atom of the scorpionate ligand and a tri­phenyl­phosphane ligand.

The silver(I) adduct [HB{3-(CF₃),5-(CH₃)Pz}₃]AgNCCH₃ was obtained by treating [HB{3-(CF₃),5-(CH₃)Pz}₃]Na with CF₃SO₃Ag in the presence of aceto­nitrile, and was isolated in 85% yield. Single-crystal X-ray diffraction analysis reveals that the Ag^I center has a pseudo-tetra­hedral all-nitro­gen coordination sphere and is supported by a tris­(pyrazol­yl)borate ligand that binds to the Ag^I center in a κ³-fashion.

Reaction of EuI₂(THF)₂ with K[HB(3,5-^iPr2pz)] (= KTp^iPr2, pz = pyrazol­yl) afforded the new europium(II) scorpionate complex (KTp^iPr2)(3,5-^iPr2pzH)₂Eu^III (1) in addition to the sterically crowded pyraza­bole derivative trans-{(3,5-^iPr2pz)HB(μ-3,5-^iPr2pz)}₂ (2) which were both structurally characterized through X-ray diffraction.

In the crystal, weak CuCl inter­actions between symmetry-related mol­ecules create a dimerization with a chloride occupying the apical position of the square-pyramidal geometry typical of many copper(II) chloride hetero-scorpionate complexes.

The metal complex is composed of a copper centre trigonal–bipyramidally surrounded by the scorpionate ligand and an acetamide ligand with a hydrogen-bonded tri­fluoro­methane­sulfonate counter-ion.

A new procedure for the synthesis of the electron-poor ligand tris­(3,4,5-tri­bromo­pyrazol-1-yl)phosphine oxide is described. The structure displays a network of halogen bonds in the solid state.