11 research outputs found

    Octakis(<i>tert</i>-butoxo)dicerium(IV) [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>]: Synthesis, Characterization, Decomposition, and Reactivity

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    An advanced synthesis for the homometallic derivative [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>] (<b>1</b>) starting from [Ce­(O<sup><i>t</i></sup>Bu)<sub>2</sub>{N­(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>] 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 [Ce<sub>3</sub>O­(O<sup><i>t</i></sup>Bu)<sub>10</sub>] and [Ce<sub>3</sub>(O<sup><i>t</i></sup>Bu)<sub>11</sub>] (<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 [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>(L)] [L = HO<sup><i>t</i></sup>Bu (<b>3</b>), OCPh<sub>2</sub> (<b>4</b>)] is described

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

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    Six novel homoleptic palladium­(II) and platinum­(II) complexes of donor-substituted alkenol ligands [PyCHC­(R)­OH; Py = pyridine, R = CH<sub>3</sub>, CF<sub>3</sub>, C<sub>2</sub>F<sub>5</sub>, C<sub>3</sub>F<sub>7</sub>] of the general formula M­[PyCHC­(R)­O]<sub>2</sub> (M = Pd, Pt) were synthesized by reacting the deprotonated ligands with PdCl<sub>2</sub> and K<sub>2</sub>PtCl<sub>4</sub>, 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 (<sup>1</sup>H, <sup>13</sup>C, and <sup>19</sup>F) 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<sub><i>x</i></sub>F<sub><i>y</i></sub> groups, resulting in an effective steric shielding of the metal atoms

    4-Tetrafluoropyridyl Silver(I), AgC<sub>5</sub>F<sub>4</sub>N, in Redox Transmetalations with Selenium and Tellurium

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    Se­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> and Te­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> were prepared via redox transmetalations of AgC<sub>5</sub>F<sub>4</sub>N 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(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·(μ-DMSO)]<sub>∞</sub> (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(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·TMTU]<sub>∞</sub> and [Te­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>·TMTU]<sub>∞</sub> (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C<sub>5</sub>F<sub>4</sub>N ligand being significantly more electron-withdrawing in comparison with the C<sub>6</sub>F<sub>5</sub> group; that is, Te­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> 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))

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    The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO<sup><i>t</i></sup>Bu produced homometallic Ce­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(NC<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (<b>1</b>) and the heterometallic derivative KCe<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>10</sub> (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce<sub>3</sub>O­(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<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<sup><i>t</i></sup>Bu)<sub>4</sub>(THF)<sub>2</sub> (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O<sup><i>t</i></sup>Bu)<sub><i>x</i></sub>]<sub><i>n</i></sub> (<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<sup><i>t</i></sup>Bu)<sub>4+<i>x</i></sub> (<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<sup><i>t</i></sup>Bu)<sub>7</sub>(NC<sub>5</sub>H<sub>5</sub>) (<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)<sub>6</sub> in boiling toluene to yield the termetallic complexes (CO)<sub>5</sub>Mo<i>M</i>(μ<sub>2</sub>-O<sup><i>t</i></sup>Bu)<sub>3</sub>Ce­(O<sup><i>t</i></sup>Bu)<sub>3</sub> (<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), AgC<sub>5</sub>F<sub>4</sub>N, in Redox Transmetalations with Selenium and Tellurium

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    Se­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> and Te­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> were prepared via redox transmetalations of AgC<sub>5</sub>F<sub>4</sub>N 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(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·(μ-DMSO)]<sub>∞</sub> (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(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·TMTU]<sub>∞</sub> and [Te­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>·TMTU]<sub>∞</sub> (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C<sub>5</sub>F<sub>4</sub>N ligand being significantly more electron-withdrawing in comparison with the C<sub>6</sub>F<sub>5</sub> group; that is, Te­(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> 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))

    No full text
    The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO<sup><i>t</i></sup>Bu produced homometallic Ce­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(NC<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (<b>1</b>) and the heterometallic derivative KCe<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>10</sub> (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce<sub>3</sub>O­(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<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<sup><i>t</i></sup>Bu)<sub>4</sub>(THF)<sub>2</sub> (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O<sup><i>t</i></sup>Bu)<sub><i>x</i></sub>]<sub><i>n</i></sub> (<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<sup><i>t</i></sup>Bu)<sub>4+<i>x</i></sub> (<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<sup><i>t</i></sup>Bu)<sub>7</sub>(NC<sub>5</sub>H<sub>5</sub>) (<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)<sub>6</sub> in boiling toluene to yield the termetallic complexes (CO)<sub>5</sub>Mo<i>M</i>(μ<sub>2</sub>-O<sup><i>t</i></sup>Bu)<sub>3</sub>Ce­(O<sup><i>t</i></sup>Bu)<sub>3</sub> (<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

    Synthetic and Structural Investigations on the Reactivity of the Cd–I Bond in [ICd{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] to Construct New Mixed-Metal Alkoxides

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    New mixed-metal alkoxides of general formula [XCd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub><i>n</i></sub> (X = −C<sub>2</sub>F<sub>5</sub>, −C<sub>6</sub>F<sub>5</sub>, −C<sub>6</sub>F<sub>4</sub>-4-H, −NO<sub>3</sub>, −NCO, −SO<sub>3</sub>CF<sub>3</sub>, −O<sub>2</sub>CCF<sub>3</sub>, −O<sub>2</sub>CC<sub>2</sub>F<sub>5</sub>, −O<sub>2</sub>CCH<sub>3</sub>, −ClO<sub>4</sub>, −CN, −SO<sub>4</sub>; <i>n</i> = 1, 2) were obtained by the scission of the Cd–I bond in the iodo heterobimetallic isopropoxide [ICd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<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<sup><i>i</i></sup>)<sub>4</sub>(HOPr<sup><i>i</i></sup>)]<sub>2</sub> and bis­(fluoroorgano)cadmium (Cd­(R<sub><i>f</i></sub><i>)</i><sub>2</sub>) compounds. The new compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, and mass spectrometry. The results of X-ray diffraction analysis of [(F<sub>5</sub>C<sub>6</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>2</b>), [(4-H-F<sub>4</sub>C<sub>6</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>3</b>), [(F<sub>5</sub>C<sub>2</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>4</b>), [(ONO<sub>2</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>5</b>), [(CH<sub>3</sub>CO<sub>2</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>6</b>), [(O<sub>2</sub>ClO<sub>2</sub>)­(H<sub>5</sub>C<sub>3</sub>N)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>7</b>), [(μ-O<sub>2</sub>ClO<sub>2</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>8</b>), [(μ-O<sub>2</sub>CCF<sub>3</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>8</sub>(O<sub>2</sub>CCF<sub>3</sub>)}]<sub>2</sub> (<b>9</b>), [(μ-O<sub>2</sub>CC<sub>2</sub>F<sub>5</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>8</sub>(O<sub>2</sub>CC<sub>2</sub>F<sub>5</sub>)}]<sub>2</sub> (<b>10</b>), [(μ­(<i>O</i>,<i>N</i>)-OCN)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>11</b>), and [(μ-O<sub>2</sub>SOCF<sub>3</sub>)­Cd­{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>12</b>) revealed the molecular framework to be formally constituted by tetradentate coordination of a nonaisopropoxo dizirconate unit, {Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}<sup>−</sup>, to a CdX<sup>+</sup> 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

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    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 CF<sub>3</sub> 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

    No full text
    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 CF<sub>3</sub> 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

    Molecular Co(II) and Co(III) Heteroarylalkenolates as Efficient Precursors for Chemical Vapor Deposition of Co<sub>3</sub>O<sub>4</sub> Nanowires

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    Two new cobalt precursors, Co<sup>II</sup>(PyCHCOCF<sub>3</sub>)<sub>2</sub>­(DMAP)<sub>2</sub> (<b>1</b>) and Co<sup>III</sup>(Py­CHCOCF<sub>3</sub>)<sub>3</sub> (<b>2</b>), based on Co­(II) and Co­(III) centers were synthesized using a redox active ligand system. The different chemical configurations of <b>1</b> and <b>2</b> and differential valence states of cobalt were confirmed by crystal structure determination and comprehensive analytical studies. Whereas <b>1</b> could not be studied by NMR due to the paramagnetic nature of the central atom, <b>2</b> was unambiguously characterized by multinuclear 1D and 2D NMR experiments in solution. Both compounds are efficient precursors for catalyst-free growth of Co<sub>3</sub>O<sub>4</sub> nanowires on Si and Al<sub>2</sub>O<sub>3</sub> substrates by a chemical vapor deposition process. The different valence states of cobalt species influenced their chemical decomposition pathways in the gas phase; for instance, <b>1</b> was partially oxidized (Co<sup>2+</sup> → Co<sup>3+</sup>), and <b>2</b> underwent reduction (Co<sup>3+</sup> → Co<sup>2+</sup>) to form pure cobaltite in both cases that verified the metal–ligand redox interplay. Co<sub>3</sub>O<sub>4</sub> nanowires with nanometric diameters (50–100 nm) were obtained irrespective of the chosen cobalt precursor. Investigations on the humidity sensing behavior of CVD deposits demonstrated their potential as promising sensor materials
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