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

Novel Air-Stable and Volatile Bis(pyridylalkenolato)palladium(II) and -platinum(II) Derivatives

Six novel homoleptic palladium­(II) and platinum­(II) complexes of donor-substituted alkenol ligands [PyCHC­(R)­OH; Py = pyridine, R = CH₃, CF₃, C₂F₅, C₃F₇] of the general formula M­[PyCHC­(R)­O]₂ (M = Pd, Pt) were synthesized by reacting the deprotonated ligands with PdCl₂ and K₂PtCl₄, respectively. Molecular structures, revealed by single-crystal X-ray diffraction analyses, showed a square-planar arrangement of ligands around palladium and platinum centers, with the pyridine-ring nitrogen atoms situated in a mutually <i>trans</i> position. The monomeric nature of the compounds in the solution state was confirmed by multinuclear (¹H, ¹³C, and ¹⁹F) NMR spectroscopy. Thermal decomposition profiles recorded under a nitrogen atmosphere suggested their potential as volatile precursors to palladium and platinum materials. The volatility was increased upon elongation of the perfluoroalkyl chain, which suppressed the intermolecular interactions, as is evident in crystal packings. The volatility of these compounds was attributed to bidentate chelation of the alkenol units and cooperativity among the electron-back-donating nitrogen atom and interplay of electron-withdrawing C_<i>x</i>F_<i>y</i> groups, resulting in an effective steric shielding of the metal atoms

4-Tetrafluoropyridyl Silver(I), AgC₅F₄N, in Redox Transmetalations with Selenium and Tellurium

Se­(C₅F₄N)₂ and Te­(C₅F₄N)₂ were prepared via redox transmetalations of AgC₅F₄N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E­(C₅F₄N)₂·(μ-DMSO)]_∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te­(C₅F₄N)₂·TMTU]_∞ and [Te­(C₆F₅)₂·TMTU]_∞ (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C₅F₄N ligand being significantly more electron-withdrawing in comparison with the C₆F₅ group; that is, Te­(C₅F₄N)₂ is the stronger Lewis acid

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

4-Tetrafluoropyridyl Silver(I), AgC₅F₄N, in Redox Transmetalations with Selenium and Tellurium

Se­(C₅F₄N)₂ and Te­(C₅F₄N)₂ were prepared via redox transmetalations of AgC₅F₄N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E­(C₅F₄N)₂·(μ-DMSO)]_∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te­(C₅F₄N)₂·TMTU]_∞ and [Te­(C₆F₅)₂·TMTU]_∞ (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C₅F₄N ligand being significantly more electron-withdrawing in comparison with the C₆F₅ group; that is, Te­(C₅F₄N)₂ is the stronger Lewis acid

Synthetic and Structural Investigations on the Reactivity of the Cd–I Bond in [ICd{Zr₂(OPr^<i>i</i>)₉}] to Construct New Mixed-Metal Alkoxides

New mixed-metal alkoxides of general formula [XCd­{Zr₂(OPr^<i>i</i>)₉}]_<i>n</i> (X = −C₂F₅, −C₆F₅, −C₆F₄-4-H, −NO₃, −NCO, −SO₃CF₃, −O₂CCF₃, −O₂CC₂F₅, −O₂CCH₃, −ClO₄, −CN, −SO₄; <i>n</i> = 1, 2) were obtained by the scission of the Cd–I bond in the iodo heterobimetallic isopropoxide [ICd­{Zr₂(OPr^<i>i</i>)₉}] (<b>1</b>), whereby the underlying synthetic strategies involve metathesis reactions with silver salts or Lewis acid–base interactions between the Brønsted acid [Zr­(OPr^<i>i</i>)₄(HOPr^<i>i</i>)]₂ and bis­(fluoroorgano)cadmium (Cd­(R_<i>f</i><i>)</i>₂) compounds. The new compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, and mass spectrometry. The results of X-ray diffraction analysis of [(F₅C₆)­Cd­{Zr₂(OPr^<i>i</i>)₉}] (<b>2</b>), [(4-H-F₄C₆)­Cd­{Zr₂(OPr^<i>i</i>)₉}] (<b>3</b>), [(F₅C₂)­Cd­{Zr₂(OPr^<i>i</i>)₉}]₂ (<b>4</b>), [(ONO₂)­Cd­{Zr₂(OPr^<i>i</i>)₉}]₂ (<b>5</b>), [(CH₃CO₂)­Cd­{Zr₂(OPr^<i>i</i>)₉}] (<b>6</b>), [(O₂ClO₂)­(H₅C₃N)­Cd­{Zr₂(OPr^<i>i</i>)₉}] (<b>7</b>), [(μ-O₂ClO₂)­Cd­{Zr₂(OPr^<i>i</i>)₉}]₂ (<b>8</b>), [(μ-O₂CCF₃)­Cd­{Zr₂(OPr^<i>i</i>)₈(O₂CCF₃)}]₂ (<b>9</b>), [(μ-O₂CC₂F₅)­Cd­{Zr₂(OPr^<i>i</i>)₈(O₂CC₂F₅)}]₂ (<b>10</b>), [(μ­(<i>O</i>,<i>N</i>)-OCN)­Cd­{Zr₂(OPr^<i>i</i>)₉}]₂ (<b>11</b>), and [(μ-O₂SOCF₃)­Cd­{Zr₂(OPr^<i>i</i>)₉}]₂ (<b>12</b>) revealed the molecular framework to be formally constituted by tetradentate coordination of a nonaisopropoxo dizirconate unit, {Zr₂(OPr^<i>i</i>)₉}⁻, to a CdX⁺ unit. In solution and in the solid state, <b>1</b>–<b>7</b> exist as monomers, whereas compounds <b>8</b>–<b>12</b> form dimers

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

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

Design of Volatile Mixed-Ligand Tantalum(V) Compounds as Precursors to Ta₂O₅ Films

Synthesis and structural characterization of six monomeric, heteroleptic tantalum­(V) complexes of the general formula Ta­(O^<i>i</i>Pr)₄(ArTFP), where Ar = pyridine (<b>1</b>), 4,5- dimethyloxazole (<b>2</b>), 4,5-dimethylthiazole (<b>3</b>), benzimidazole (<b>4</b>), benzoxazole (<b>5</b>), benzthiazole (<b>6</b>), and TFP = trifluoropropenol, are described. Introduction of a donor-functionalized β-heteroarylalkenolate in the coordination sphere of Ta in the dimeric Ta₂(O^<i>i</i>Pr)₁₀ increases significantly the stability and volatility of these precursors, simplifying the depositions of Ta₂O₅. The molecular structures of <b>1</b>–<b>6</b> exhibited a distorted octahedral coordination around the tantalum center by four isopropoxide groups and one β-heteroarylalkenolate. Thermal decomposition studies (TG/DTA) and analysis of byproducts by NMR spectroscopy confirmed the decomposition mechanism and gas-phase stability of the heteroleptic compounds necessary for Ta₂O₅ depositions. Chemical vapor deposition studies with <b>1</b> and <b>2</b> demonstrated their suitability as efficient precursors for the growth of Ta₂O₅ thin films, whose properties were compared with Ta₂O₅ thin films obtained from homoleptic alkoxides