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
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 [CeÂ(O<sup><i>t</i></sup>Bu)<sub>2</sub>{NÂ(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>] was
developed. Structural characterization of a ceriumÂ(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>OÂ(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
Six novel homoleptic palladiumÂ(II) and platinumÂ(II) complexes
of
donor-substituted alkenol ligands [PyCHCÂ(R)ÂOH; 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 MÂ[PyCHCÂ(R)ÂO]<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
SeÂ(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> and TeÂ(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 [EÂ(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 [TeÂ(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·TMTU]<sub>∞</sub> and [TeÂ(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, TeÂ(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))
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 CeÂ(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>OÂ(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<b>2</b>) was obtained
from a solution of ceriumÂ(IV) tetrakisÂ(<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 CeÂ(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>CeÂ(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>CeÂ(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 MoÂ(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>CeÂ(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
SeÂ(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub> and TeÂ(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 [EÂ(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 [TeÂ(C<sub>5</sub>F<sub>4</sub>N)<sub>2</sub>·TMTU]<sub>∞</sub> and [TeÂ(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, TeÂ(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))
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 CeÂ(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>OÂ(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<b>2</b>) was obtained
from a solution of ceriumÂ(IV) tetrakisÂ(<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 CeÂ(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>CeÂ(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>CeÂ(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 MoÂ(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>CeÂ(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
New
mixed-metal alkoxides of general formula [XCdÂ{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 [ICdÂ{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 [ZrÂ(OPr<sup><i>i</i></sup>)<sub>4</sub>(HOPr<sup><i>i</i></sup>)]<sub>2</sub> and bisÂ(fluoroorgano)cadmium (CdÂ(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>)ÂCdÂ{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>)ÂCdÂ{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>3</b>),
[(F<sub>5</sub>C<sub>2</sub>)ÂCdÂ{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}]<sub>2</sub> (<b>4</b>), [(ONO<sub>2</sub>)ÂCdÂ{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>)ÂCdÂ{Zr<sub>2</sub>(OPr<sup><i>i</i></sup>)<sub>9</sub>}] (<b>6</b>), [(O<sub>2</sub>ClO<sub>2</sub>)Â(H<sub>5</sub>C<sub>3</sub>N)ÂCdÂ{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>)ÂCdÂ{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>)ÂCdÂ{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>)ÂCdÂ{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>), [(μÂ(<i>O</i>,<i>N</i>)-OCN)ÂCdÂ{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>)ÂCdÂ{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
Multiple
silverÂ(I)-auratesÂ(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
Multiple
silverÂ(I)-auratesÂ(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
Two
new cobalt precursors, Co<sup>II</sup>(PyCHCOCF<sub>3</sub>)<sub>2</sub>Â(DMAP)<sub>2</sub> (<b>1</b>) and Co<sup>III</sup>(PyÂCHCOCF<sub>3</sub>)<sub>3</sub> (<b>2</b>), based on CoÂ(II) and CoÂ(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