Revitalisation of group IV metal-oxo clusters: synthetic approaches, structural motifs and applications.

Group (IV) metal oxo clusters represent a unique family of molecular species that are increasingly being utilized in applications ranging from catalysis and materials chemistry to electronics, and sensors. These clusters exhibit distinctive structural features, chemical reactivity, and electronic structure. Nevertheless, their full potential has yet to be fully realized due to the lack of deeper understanding regarding their structure and formation mechanisms, inherent traits, and intricacies in their design, which could ultimately enable significant customization of their properties and overall behaviour.

Hafnium(IV) Chemistry with Imide-Dioxime and Catecholate-Oxime Ligands: Unique {Hf} and Metalloaromatic {Hf}-Oxo Clusters Exhibiting Fluorescence.

Hafnium(IV) molecular species have gained increasing attention due to their numerous applications ranging from high-resolution nanolithography, heterogeneous catalysis, and electronics to the design of molecule-based building blocks in metal-organic frameworks (MOFs), with applications in gas separation, sorption, luminescence sensing, and interim storage of radioactive waste. Despite great potential, their chemistry is relatively underdeveloped. Here, we use strong chelators (2-6)-piperidine-2,6-dione (Hpidiox) and 2,3-dihydroxybenzaldehyde oxime (Hdihybo) to synthesize the first ever reported pentanuclear {Hf/Hpidiox} and hexanuclear {Hf/Hdihybo} clusters (HfOCs).

Acid/base responsive assembly/dis-assembly of a family of zirconium(IV) clusters with a cyclic imide-dioxime ligand.

The hydrolytically stable dioxime ligand (2-6)-piperidine-2,6-dione (Hpidiox) acts as a strong chelator mainly with hard metals in high oxidation states, a pre-requisite for potential applications in metal sequestering processes from aqueous solutions. Reaction of ZrCl with Hpidiox in methanol gives the mononuclear compound [Zr(η,η,η-Hpidiox-,,')(OH)]Cl·HO·CHOH (1), while the same reaction mixture in the presence of KOH gave the pentanuclear ZrOC [ZrIV5(μ-OH)(OH)(μ-η,η,η-Hpidiox-,,')(η,η,η-Hpidiox,,')]·5KCl·3CHOH·8HO (2). Compound 1 is formed at very acidic pH = 0, and the pentanuclear ZrOC 2 at higher pH values (pH = 2).

Synthesis, Structural and Physicochemical Characterization of a Titanium(IV) Compound with the Hydroxamate Ligand ,2-Dihydroxybenzamide.

The siderophore organic ligand ,2-dihydroxybenzamide (Hdihybe) incorporates the hydroxamate group, in addition to the phenoxy group in the ortho-position and reveals a very rich coordination chemistry with potential applications in medicine, materials, and physical sciences. The reaction of Hdihybe with TiCl in methyl alcohol and KOH yielded the tetranuclear titanium oxo-cluster (TOC) [Ti(μ-O)(HOCH)(-Hdihybe)(Hdihybe)]Cl∙10HO∙12CHOH (). The titanium compound was characterized by single-crystal X-ray structure analysis, ESI-MS, C, and H NMR spectroscopy, solid-state and solution UV-Vis, IR vibrational, and luminescence spectroscopies and molecular orbital calculations.

Synthesis, Structural, and Physicochemical Characterization of a Ti and a Unique Type of Zr Oxo Clusters Bearing an Electron-Rich Unsymmetrical {OON} Catecholate/Oxime Ligand and Exhibiting Metalloaromaticity.

The chelating catechol/oxime ligand 2,3-dihydroxybenzaldehyde oxime (Hdihybo) has been used to synthesize one titanium(IV) and two zirconium(IV) compounds that have been characterized by single-crystal X-ray diffraction and H and C NMR, solid-state UV-vis, and ESI-MS spectroscopy. The reaction of TiCl with Hdihybo and KOH in methanol, at ambient temperature, yielded the hexanuclear titanium(IV) compound K[Ti(μ-O)(μ-O)(OCH)(CHOH)(μ-Hdihybo)]·CHOH (), while the reaction of ZrCl with Hdihybo and either BuNOH or KOH also gave the hexanuclear zirconium(IV) compounds and , respectively. Compounds - have the same structural motif [M(μ-Ο)(μ-Ο)] (M = Ti, Zr), which constitutes a unique example with a trigonal-prismatic arrangement of the six zirconium atoms, in marked contrast to the octahedral arrangement of the six zirconium atoms in all the Zr clusters reported thus far, and a unique Zr core structure.

Synthesis, structural and physicochemical characterization of a new type Ti-oxo cluster protected by a cyclic imide dioxime ligand.

Reaction of the cyclic ligand (2Z,6Z)-piperidine-2,6-dione dioxime with TiCl4 and KOH yielded the hexanuclear cluster K6[TiIV6(μ3-O)2(μ2-O)3(CH3O)6(μ2-η1,η1,η2-Hpidiox-O,N,O')4(μ2-η1,η1,η2-pidiox-O,N,O')2]·7.5CH3OH possessing a new {Ti6O5} structural motif. The cluster core {Ti6O5} is wrapped by external tripodal imide dioxime ligands, showing good solubility and stability and thus, allowing its solution to be studied by means of electrospray ionization mass spectrometry, electrochemistry and 2D NMR, c.

Synthesis, Bonding, and Reactivity of Vanadium(IV) Oxido-Fluorido Compounds with Neutral Chelate Ligands of the General Formula cis-[V(IV)(═O)(F)(L(N-N))2](+).

Reaction of the oxidovanadium(IV)-L(N-N) species (L(N-N) is bipy = 2,2'-bipyridine or bipy-like molecules) with either BF4(-) or HF and/or KF results in the formation of compounds of the general formula cis-[V(IV)(═O)(F)(L(N-N))2](+). Structural and spectroscopic (electron paramagnetic resonance) characterization shows that these compounds are in the tetravalent oxidation state containing a terminal fluorido ligand. Density functional theory calculations reveal that the V(IV)-F bond is mainly electrostatic, which is reinforced by reactivity studies that demonstrate the nucleophilicity of the fluoride ligand in a halogen exchange reaction and in fluorination of various organic substrates.