Scorpionate chemistry at the 50th anniversary

The Guest Editors of the special issue entitled `Scorpionates: a golden anniversary', Glenn Yap and Kiyoshi Fujisawa, introduce the collection of invited papers celebrating the 50th anniversary of the discovery of scorpionate chemistry and highlight the current productive state of the subject.

Mono- and binuclear tris­(3-tert-butyl-2-sulfanyl­idene-1H-imidazol-1-yl)hydro­borate bis­muth(III) dichloride complexes: a soft scorpionate ligand can coordinate to p-block elements

The structure of a new mononuclear bis­muth(III) complex with the soft scorpionate ­(3-tert-butyl-2-sulfanyl­idene-1H-imidazol-1-yl)hydro­borate ligand is compared with that of the binuclear derivative.

New homodinuclear tris­(3-alkyl­pyrazol­yl)borate complexes of Co^II and Ni^II with a tetra­acetyl­ethane dianion as a bridging ligand

Two new homodinuclear tris­(3-alkyl­pyrazol­yl)borate complexes of Co^II and Ni^II with a tetra­acetyl­ethane dianion as the bridging ligand were synthesized and characterized by mass spectrometry and X-ray crystallography. A significant deviation from orthogonality between the acetyl­acetonate planes was observed in the two complexes.

Comparison of thallium(I) complexes with mesityl-substituted tris­(pyrazolyl)hydroborate ligands, [Tl{HB(3-Ms-5-Mepz)₃}] and [Tl{HB(3-Ms-5-Mepz)₂(3-Me-5-Mspz)}]

The structures of thallium(I) complexes with two different mesityl-substituted ligands, i.e. tris(3-mesityl-5-methylpyrazol-1-yl)hydroborate and bis(3-mesityl-5-methylpyrazol-1-yl)(5-mesityl-3-methylpyrazol-1-yl)hydroborate, are compared. The shape of the former thallium(I) complex can be considered as a vase and the latter as a baseball glove.

Steric and electronic factor comparisons in hydro­tris­(3-phenyl­pyrazol­yl)borate nickel(II) aryl­oxides

Although [hydro­tris­(3-phenyl­pyrazol­yl)borato]nickel(II) (denoted Tp^PhNi^II) complexes can have biological significance as metalloenzyme models, none have been reported. To provide insight into the coordination environment afforded by this ligand, three Tp^PhNi^II complexes with aryl­oxides of varying steric and electronic effects are compared.

An iron(II) complex tripodally chelated with 1,1,1-tris­(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour

In the novel iron(II) complex salt tetra­phenyl­phospho­nium tris­(thio­cyanato)[1,1,1-tris­(pyridin-2-yl)ethane]­ferrate(II), the Fe—N bond lengths indicate that the specimen consists of comparable molar fractions of the low- and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place around 290 K.

An unusual bis-heteroscorpionate complex with anomalous ligands: [tris­(3,4-di­bromo-5-phenyl­pyrazol­yl)hydro­borato][hydro­tris­(3-neo­pentyl­pyrazol­yl)borato]nickel(II)

Two atypical tris­pyrazolylborate ligands were selected to make a heteroscorpionate complex in order to showcase the flexibility of steric and electronic effects easily afforded by this class of facial tridentate ligands.

Mol­ecular structures of tris­(1-tert-butyl-2-mercapto­imidazol­yl)hydro­borate complexes of titanium, zirconium and hafnium

The structural characterization of the tris(1-tert-butyl-2-mercaptoimidazol­yl)hydro­borate, [Tm], complexes Cp[κ³S₂,H-Tm]MCl₂ (M = Zr and Ti) by X-ray diffraction demonstrates that the [Tm] ligand coordinates in a κ³S₂,H mode, while the benzyl compounds [Tm]M(CH₂Ph)₃ (M = Zr and Hf) exhibit κ³S₃ coordination.

FcTp(R) (R = ⁱPr or ^tBu): third-generation ferrocenyl scorpionates

Thallium(I) and cobalt(II) halide complexes of the ferrocenyltris(3-R-pyrazol­yl)borate ligand (FcTp^R, with R = ⁱPr or ^tBu) have been synthesized and their structural characteristics determined to expand the range of redox-active third-generation scorpionates.

The structures of two scorpionates: thallium tetra­kis­(3-phenyl-1H-pyrazol-1-yl)borate and potassium tetra­kis­(3-cyclo­propyl-1H-pyrazol-1-yl)borate

The different motifs present in the Cambridge Structural Database concerning tetra­kis­pyrazolylborates have been analyzed and two new structures, a Tl⁺ and a K⁺ salt, resolved. Compared with the previously reported motifs, one of them is new.

Silver(I) and rhenium(I) metal complexes of a 2,2′-bi­pyridine-functionalized third-generation tris­(pyrazol­yl)methane ligand

The heteroditopic Bipy–CH₂–O–CH₂–C(pz)₃ ligand (Bipy-L; Bipy is 2,2′-bi­pyridine and pz is pyrazol­yl) reacts with Ag^I and Re^I metallic centers to yield the {[Ag(μ-Bipy-L)]BF₄·0.5Et₂O}_n coordination polymer and the [ReBr(Bipy-L)(CO)₃] monometallic compound.

A cadmium(II) coordination polymer formed from a third generation tetra­topic tris­(pyrazol­yl)methane ligand

The cadmium(II) complex of the tetra­topic ligand 1,2,4,5-C₆H₂[CH₂OCH₂C(pz)₃]₄ (pz is pyrazolyl) consists of a one-dimensional coordination polymer, {1,2,4,5-C₆H₂[(CH₂OCH₂C(pz)₃]₄Cd₂(BF₄)₄}_n, showing infinite chains of 32-atom metallomacrocycles.

Side-on coordination mode of a pyrazolyl group in the structure of a divalent [Sm{B(3-Mepz)₄}₂] complex (3-Mepz is 3-methyl­pyrazol-1-yl)

Bis[tetra­kis­(3-methyl-1H-pyrazol-1-yl)borato]samarium(II) was synthesized by the reaction of SmI₂ with potassium tetra­kis­(3-methyl­pyrazol­yl)borate in tetrahydrofuran. The X-ray structure analysis revealed an unusual side-on coordination mode of a 3-methyl­pyrazolyl group through an N=N group in the B(3-Mepz)₄ ligand. The distortion is defined by the B—N—N—Sm torsion angle [85.5 (4)°].

A pseudo­tetra­hedral nickel(II) complex with a tridentate oxazoline-based scorpionate ligand: chlorido­[tris­(4,4-di­methyl­oxazolin-2-yl)phenyl­borato]nickel(II)

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.

A new synthetic route to the electron-deficient ligand tris­(3,4,5-tri­bromo­pyrazol-1-yl)phosphine oxide

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.

Nitrile coordination to rhodium does not lead to C—H activation

Tris(pyrazol­yl)borate complexes of rhodium are well known to activate C—H bonds. The reactive [Tp′Rh(PMe₃)] fragment [Tp′ is tris­(3,5-di­methyl­pyrazol-1-yl)hydro­borate] is found to react with valero­nitrile to give a κ¹N-bound complex. In contrast to the widespread evidence for the reaction of this fragment with C—H bonds via oxidative addition, no evidence for such a complex is observed.

The silver(I) complex [HB{3-(CF₃),5-(CH₃)Pz}₃]AgNCCH₃ supported by a partially fluorinated scorpionate 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.

The non-isomorphous crystal structures of NHC—Au—Cl and NHC—Au—Br (NHC is 1,3-di­benzyl-4,5-di­phenyl­imidazol-2-yl­idene)

The chemically analogous chloride and bromide complexes NHC–Au–Cl and NHC–Au–Br (NHC is an N-heterocyclic carbene) have significantly different crystal structures, and the bromide compound displays variability in its metal–ligand distances.

A synchrotron study of [5,10,15,20-tetra­kis­(3-cyano­phen­yl)porphyrinato-κ⁴N⁵,N¹⁰,N¹⁵,N²⁰]copper(II) nitro­benzene tris­olvate at 80 K

[5,10,15,20-Tetra­kis(3-cyano­phen­yl)porphyrinato]copper(II) exhibits a C_2h-symmetric ααββ conformation, despite an unsymmetrical crystal environment, and is situated on a crystallographic centre of symmetry. The Cu^II ion adopts a genuine square-planar coordination by the four pyrrole N atoms.

Conformational differences and inter­molecular C—H⋯N inter­actions in three polymorphs of a bis­(pyridin­yl)-substituted benzimidazole

The C—H⋯N inter­actions in three polymorphs of 5,6-dimethyl-2-(pyridin-2-yl)-1-[(pyridin-2-yl)meth­yl]-1H-benzimidazole are compared. Inter­action energies for pairs of mol­ecules are calculated using density functional theory.

Engineering crystals that facilitate the acyl-transfer reaction: insight from a comparison of the crystal structures of myo-inositol-1,3,5-orthoformate-derived benzoates and carbonates

The crystal structures of the benzoate, carbonate and thio­carbonate derivatives of myo-inositol 1,3,5-orthoformate are compared and correlated with their inter­molecular acyl-transfer reactivity. Compounds that showed facile inter­molecular acyl-transfer reactivity showed a favourable orientation of the reactive groups, i.e. electrophile (C=O) to nucleophile (–OH), with the requisite geometry in their crystal structures. In contrast, compounds that did not exhibit inter­molecular acyl-transfer reactions are devoid of reactive geometry.

Synthesis and characterization of four organic–inorganic salts: sulfates of 2-amino­pyridinium derivatives

The synthesis, crystal structures and Hirshfeld surface analysis of four new organic–inorganic salts are reported. Extensive three-dimensional hydrogen-bonding patterns are formed.

Structure and third-order nonlinear optical properties of the two-dimensional Co^II coordination polymer [Co(1,2-BIB)(PA)]_n {1,2-BIB is 1,2-bis­[(1H-imidazol-1-yl)meth­yl]benzene and H₂PA is phthalic acid}

A two-dimensional Co^II coordination polymer exhibits excellent third-order nonlinear absorption and self-focusing effects. The third-order nonlinear optical susceptibility χ⁽³⁾ is 1.07 × 10⁻⁸ esu.

A new three-dimensional manganese(II) coordination polymer based on the 1,3,5-tris­[(1H-imidazol-1-yl)meth­yl]benzene ligand

In the crystal structure of a new Mn^II complex, obtained using flexible imidazole-containing 1,3,5-tris­[(1H-imidazol-1-yl)meth­yl]benzene (timb) ligands with manganese sulfate through solvothermal reaction, the Mn^II atom adopts an octa­hedral geometry and adjacent Mn^II centres are linked by timb ligands to generate a two-dimensional layered structure. The two-dimensional sheets are further connected into a three-dimensional porous network by bridging anionic sulfate ligands.

Ethyl 4-(9H-carbazol-9-yl)benzoate: fivefold superstructure with ten crystallographically independent mol­ecules refined from a twinned crystal

The crystal structure of ethyl 4-(9H-carbazol-9-yl)benzoate revealed a surprisingly large number of independent mol­ecules per unit cell and an intricate packing motif.

Hydrogen-bonding synthons in lamotrigine salts: 3,5-di­amino-6-(2,3-di­chloro­phen­yl)-1,2,4-triazin-2-ium 2-[(2-carb­oxy­phen­yl)disulfan­yl]benzoate in its monohydrate and anhydrous forms

Two forms of lamotrigine di­thio­benzoate (i.e. the hydrate and the anhydrous form) have as the main structural motif a hydrogen-bonded tetra­mer made up of three concatenated (8) elemental synthons.

Syntheses, structures and properties of two new isostructural zinc(II) complexes based on 1-[(benzotriazol-1-yl)meth­yl]-1H-imidazole

Two new isostructural zinc(II) complexes based on the 1-[(benzotriazol-1-yl)meth­yl]-1H-imidazole (bmi) ligand exhibit mononuclear structures, in which the bmi ligands coordinate to the central metal ions in a monodentate mode.