Octakis(<i>tert</i>-butoxo)dicerium(IV) [Ce₂(O^<i>t</i>Bu)₈]: Synthesis, Characterization, Decomposition, and Reactivity

An advanced synthesis for the homometallic derivative [Ce₂(O^<i>t</i>Bu)₈] (<b>1</b>) starting from [Ce­(O^<i>t</i>Bu)₂{N­(SiMe₃)₂}₂] was developed. Structural characterization of a cerium­(IV) complex and its decomposition products confirmed the coexistence of both ether elimination and Ce–O bond cleavage processes, which lead to the formation of [Ce₃O­(O^<i>t</i>Bu)₁₀] and [Ce₃(O^<i>t</i>Bu)₁₁] (<b>2</b>) derivatives, respectively. Variable-temperature NMR spectroscopy under strict exclusion of moisture enabled insight into the decomposition processes in noncoordinating solvents and at elevated temperature. In addition, structural analysis of the heterovalent <b>2</b> and of two new complexes of the general formula [Ce₂(O^<i>t</i>Bu)₈(L)] [L = HO^<i>t</i>Bu (<b>3</b>), OCPh₂ (<b>4</b>)] is described

Heterobi- and Trimetallic Cerium(IV) <i>tert</i>-Butoxides with Mono‑, Di‑, and Trivalent Metals (<i>M</i> = K(I), Ge(II), Sn(II), Pb(II), Al(III), Fe(III))

The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO^<i>t</i>Bu produced homometallic Ce­(O^<i>t</i>Bu)₄(NC₅H₅)₂ (<b>1</b>) and the heterometallic derivative KCe₂(O^<i>t</i>Bu)₁₀ (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce₃O­(O^<i>t</i>Bu)₉ (<b>2</b>) was obtained from a solution of cerium­(IV) tetrakis­(<i>tert</i>-butoxide) in <i>n</i>-heptane under stringent precautions to avoid any adventitious hydrolysis. Lewis acid-base reactions of in situ generated Ce­(O^<i>t</i>Bu)₄(THF)₂ (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O^<i>t</i>Bu)_<i>x</i>]_<i>n</i> (<i>M</i> = Ge, Sn; <i>x</i> = 2; <i>n</i> = 2; <i>M</i> = Pb, <i>x</i> = 2; <i>n</i> = 3; <i>M</i> = Al, Fe; <i>x</i> = 3; <i>n</i> = 2) resulted in volatile products of the general formula <i>M</i>Ce­(O^<i>t</i>Bu)_4+<i>x</i> (<i>M</i> = Al (<b>4</b>), Fe (<b>5</b>); <i>x</i> = 3; <i>M</i> = Ge (<b>8</b>), Sn (<b>9</b>), Pb (<b>10</b>); <i>x</i> = 2) in high yields. By dissolving <b>4</b> and <b>5</b> in pyridine the solvent adducts <i>M</i>Ce­(O^<i>t</i>Bu)₇(NC₅H₅) (<i>M</i> = Al (<b>6</b>), Fe (<b>7</b>)) were formed, whereas <b>8</b> and <b>9</b> reacted with Mo­(CO)₆ in boiling toluene to yield the termetallic complexes (CO)₅Mo<i>M</i>(μ₂-O^<i>t</i>Bu)₃Ce­(O^<i>t</i>Bu)₃ (<i>M</i> = Ge (<b>11</b>), Sn (<b>12</b>)). The new compounds were characterized by comprehensive spectral studies, mass spectroscopy, and single crystal X-ray diffraction analysis

Heterobi- and Trimetallic Cerium(IV) <i>tert</i>-Butoxides with Mono‑, Di‑, and Trivalent Metals (<i>M</i> = K(I), Ge(II), Sn(II), Pb(II), Al(III), Fe(III))

The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO^<i>t</i>Bu produced homometallic Ce­(O^<i>t</i>Bu)₄(NC₅H₅)₂ (<b>1</b>) and the heterometallic derivative KCe₂(O^<i>t</i>Bu)₁₀ (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce₃O­(O^<i>t</i>Bu)₉ (<b>2</b>) was obtained from a solution of cerium­(IV) tetrakis­(<i>tert</i>-butoxide) in <i>n</i>-heptane under stringent precautions to avoid any adventitious hydrolysis. Lewis acid-base reactions of in situ generated Ce­(O^<i>t</i>Bu)₄(THF)₂ (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O^<i>t</i>Bu)_<i>x</i>]_<i>n</i> (<i>M</i> = Ge, Sn; <i>x</i> = 2; <i>n</i> = 2; <i>M</i> = Pb, <i>x</i> = 2; <i>n</i> = 3; <i>M</i> = Al, Fe; <i>x</i> = 3; <i>n</i> = 2) resulted in volatile products of the general formula <i>M</i>Ce­(O^<i>t</i>Bu)_4+<i>x</i> (<i>M</i> = Al (<b>4</b>), Fe (<b>5</b>); <i>x</i> = 3; <i>M</i> = Ge (<b>8</b>), Sn (<b>9</b>), Pb (<b>10</b>); <i>x</i> = 2) in high yields. By dissolving <b>4</b> and <b>5</b> in pyridine the solvent adducts <i>M</i>Ce­(O^<i>t</i>Bu)₇(NC₅H₅) (<i>M</i> = Al (<b>6</b>), Fe (<b>7</b>)) were formed, whereas <b>8</b> and <b>9</b> reacted with Mo­(CO)₆ in boiling toluene to yield the termetallic complexes (CO)₅Mo<i>M</i>(μ₂-O^<i>t</i>Bu)₃Ce­(O^<i>t</i>Bu)₃ (<i>M</i> = Ge (<b>11</b>), Sn (<b>12</b>)). The new compounds were characterized by comprehensive spectral studies, mass spectroscopy, and single crystal X-ray diffraction analysis

Single-Source Precursors for Alloyed Gold–Silver Nanocrystals - A Molecular Metallurgy Approach

Multiple silver­(I)-aurates­(I) have been prepared by salt metathesis reactions that act as efficient single-source precursors to colloidal gold silver alloys with the highest possible atom economy in the chemical synthesis of nanostructures. The CF₃ group present on the Au cation acts as an in situ reducing agent and can be converted into CO ligands by simple hydrolysis. This ligand-mediated activation and subsequent decomposition of metal–organic precursors impose a molecular control over the nucleation process, producing homogeneously alloyed (Ag–Au) nanoparticles with an atomic Au:Ag ratio of 1:1. The concept also works for the Au–Cu system and acts as a pointer to replace Au (Ag) with less expensive (Cu) metals

Interdependence of Structure, Morphology, and Phase Transitions in CVD Grown VO₂ and V₂O₃ Nanostructures

Phase selective chemical vapor deposition of nanostructured vanadium dioxide (VO₂) and sesquioxide (V₂O₃) was achieved by deploying [V­(O<i>R</i>)₄]_<i>n</i> (<i>R</i> = ^<i>t</i>Bu, <i>n</i> = 1 (<b>1</b>), <i>R</i> = Et, <i>n</i> = 3 (<b>2</b>), <i>R</i> = Me, <i>n</i> = 4 (<b>3</b>)). Use of [V­(O^<i>t</i>Bu)₄] (<b>1</b>) produced thin films of monoclinic VO₂ (M1) at 700 and 800 °C consisting of anisotropic nanostructures with high crystallinity and small hysteresis in the metal-to-semiconductor transition (MST). Film morphologies manifested strong dependence on growth temperatures and exhibited pronounced texturing effects at high temperatures (>700 °C). The microstructure of the films was found to significantly affect the MST behavior of VO₂ films. DTA measurements of VO₂ films showed MST at 63 °C (700 °C) and 65 °C (800 °C), much lower than the transition temperature observed in single crystal material (68 °C). Precursors were characterized in the solid state (XRD) and solution state (temperature dependent EPR, NMR) to reveal an association–dissociation equilibrium in solution (complexes <b>2</b> and <b>3</b>), involving monomeric, dimeric, and oligomeric species. Use of <b>2</b> and <b>3</b> as single precursors produced thin films of crystalline V₂O₃ consisting of nanosheets (5 nm) with a flower-like morphology

Single-Source Precursors for Alloyed Gold–Silver Nanocrystals - A Molecular Metallurgy Approach

Multiple silver­(I)-aurates­(I) have been prepared by salt metathesis reactions that act as efficient single-source precursors to colloidal gold silver alloys with the highest possible atom economy in the chemical synthesis of nanostructures. The CF₃ group present on the Au cation acts as an in situ reducing agent and can be converted into CO ligands by simple hydrolysis. This ligand-mediated activation and subsequent decomposition of metal–organic precursors impose a molecular control over the nucleation process, producing homogeneously alloyed (Ag–Au) nanoparticles with an atomic Au:Ag ratio of 1:1. The concept also works for the Au–Cu system and acts as a pointer to replace Au (Ag) with less expensive (Cu) metals

Air-Stable Gadolinium Precursors for the Facile Microwave-Assisted Synthesis of Gd₂O₃ Nanocontrast Agents for Magnetic Resonance Imaging

Using metal organic precursors in materials synthesis remains a challenge due to their high moisture susceptibility. In this work, we describe a facile methodology for the synthesis of Gd₂O₃-based contrast agents from two new gadolinium-based complexes. [Gd­(PyTFP)₄] (PyH) <b>1</b> (PyTFP = C₈H₅NOF₃, Py = C₅H₅N) and [Gd­(DMOTFP)₃Py] <b>2</b> (DMOTFP = C₈H₇NO₂F₃) were synthesized via a classical ligand exchange reaction of [Gd­{N­(SiMe₃)₂}₃] under inert conditions. As a result, X-ray diffraction analysis revealed a distorted square antiprismatic coordination and an augmented triangular prismatic arrangement of ligands around gadolinium atoms in <b>1</b> and <b>2</b>, respectively. It also showed that <b>1</b> is an anionic complex of formula [Gd­(PyTFP)₄]­(PyH), while a neutral tris-compound, [Gd­(DMOTFP)₃Py], was obtained as a pyridine adduct in <b>2</b>. Fast and reproducible microwave-assisted decomposition of <b>1</b> and <b>2</b> provided homogeneous Gd­(OH)₃ nanorods at mild temperature without using any surfactant or capping reagent. As-synthesized nanorods were easily transformed into a cubic phase of Gd₂O₃ nanoparticles by thermal treatment under ambient conditions. The magnetic measurement showed the typical paramagnetic behavior of the Gd₂O₃ nanoparticles (NPs). The cytotoxicity profile demonstrates the biocompatibility and negligible toxicity of the as-synthesized nanoprobes. The suggested approach provides a new class of gadolinium-based precursors which allows facile synthesis of highly crystalline Gd₂O₃ NPs