9 research outputs found
Rhenium Complex with Noninnocent Dioxolene Ligand: Combined Experimental and ab Initio Study of [(3,5-di-<i>tert</i>-Bu<sub>2</sub>C<sub>6</sub>H<sub>2</sub>O<sub>2</sub>)ReCl<sub>3</sub>(OPPh<sub>3</sub>)]
Reaction of [ReOCl<sub>3</sub>(PPh<sub>3</sub>)<sub>2</sub>] with 3,5-di-<i>tert</i>-butyl-1,2-benzoquinone
(3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-<i>tert</i>-Bu<sub>2</sub>C<sub>6</sub>H<sub>2</sub>O<sub>2</sub>)ĀReĀ(OPPh<sub>3</sub>)ĀCl<sub>3</sub>] (<b>1</b>), which was
isolated and characterized by elemental analysis, IR, UVāvis
spectroscopy, and cyclic voltammetry. In order to clarify the charge
state of rhenium and the coordinated dioxolene ligand, X-ray experiments
at 150 and 290 K were carried out. The CāO, CāC, and
ReāO bond distances at both 150 and 290 K fall between those
for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms;
an empirical āmetrical oxidation stateā of the dioxolene
ligand was estimated to be ā1.5. High-level <i>ab initio</i> calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature
of the triplet ground state of complex <b>1</b> corresponding
to a superposition of the <i>Re</i><sup><i>IV</i></sup>ā<i>SQ</i> and <i>Re</i><sup><i>V</i></sup>ā<i>cat</i> forms. In agreement
with the high-level <i>ab initio</i> and DFT calculations,
the temperature dependence of the magnetic susceptibility (5ā300
K) is well described in the assumption of the triplet ground state,
with the anomalously large zero-field splitting (ZFS) arising from
the spināorbit coupling. According to the <i>ab initio</i> calculations, all absorption bands in the visible region of the
electronic absorptions spectrum are assigned to the LMCT bands, with
significant contribution of the intraligand transition in the most intense band
at 555 nm
Rhenium Complex with Noninnocent Dioxolene Ligand: Combined Experimental and ab Initio Study of [(3,5-di-<i>tert</i>-Bu<sub>2</sub>C<sub>6</sub>H<sub>2</sub>O<sub>2</sub>)ReCl<sub>3</sub>(OPPh<sub>3</sub>)]
Reaction of [ReOCl<sub>3</sub>(PPh<sub>3</sub>)<sub>2</sub>] with 3,5-di-<i>tert</i>-butyl-1,2-benzoquinone
(3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-<i>tert</i>-Bu<sub>2</sub>C<sub>6</sub>H<sub>2</sub>O<sub>2</sub>)ĀReĀ(OPPh<sub>3</sub>)ĀCl<sub>3</sub>] (<b>1</b>), which was
isolated and characterized by elemental analysis, IR, UVāvis
spectroscopy, and cyclic voltammetry. In order to clarify the charge
state of rhenium and the coordinated dioxolene ligand, X-ray experiments
at 150 and 290 K were carried out. The CāO, CāC, and
ReāO bond distances at both 150 and 290 K fall between those
for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms;
an empirical āmetrical oxidation stateā of the dioxolene
ligand was estimated to be ā1.5. High-level <i>ab initio</i> calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature
of the triplet ground state of complex <b>1</b> corresponding
to a superposition of the <i>Re</i><sup><i>IV</i></sup>ā<i>SQ</i> and <i>Re</i><sup><i>V</i></sup>ā<i>cat</i> forms. In agreement
with the high-level <i>ab initio</i> and DFT calculations,
the temperature dependence of the magnetic susceptibility (5ā300
K) is well described in the assumption of the triplet ground state,
with the anomalously large zero-field splitting (ZFS) arising from
the spināorbit coupling. According to the <i>ab initio</i> calculations, all absorption bands in the visible region of the
electronic absorptions spectrum are assigned to the LMCT bands, with
significant contribution of the intraligand transition in the most intense band
at 555 nm
pH-Controlled One Pot Syntheses of Giant Mo<sub>2</sub>O<sub>2</sub>S<sub>2</sub>āContaining Seleno-Tungstate Architectures
Self-assembly reactions
of Na<sub>2</sub>WO<sub>4</sub>, SeO<sub>2</sub>/SeO<sub>3</sub><sup>2ā</sup>, and [Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> give, depending
on the pH value, two new large polyoxometalate complexes: i.e., [(Ī³-Se<sub>2</sub>W<sub>14</sub>O<sub>52</sub>)<sub>3</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>)<sub>6</sub>]<sup>24ā</sup> (<b>1</b>) isolated at
pH 3.5 and [(Ī³-Se<sub>2</sub>W<sub>14</sub>O<sub>52</sub>)<sub>4</sub>Ā(WO<sub>3</sub>(H<sub>2</sub>O))<sub>8</sub>Ā(W<sub>2</sub>O<sub>5</sub>)<sub>2</sub>Ā(W<sub>4</sub>O<sub>12</sub>)<sub>2</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>)<sub>4</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(SeO<sub>3</sub>))<sub>4</sub>]<sup>36ā</sup> (<b>2</b>) isolated at pH 2.
Both compounds were characterized in the solid state by single-crystal
X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in
solution by ESI-MS and NMR
pH-Controlled One Pot Syntheses of Giant Mo<sub>2</sub>O<sub>2</sub>S<sub>2</sub>āContaining Seleno-Tungstate Architectures
Self-assembly reactions
of Na<sub>2</sub>WO<sub>4</sub>, SeO<sub>2</sub>/SeO<sub>3</sub><sup>2ā</sup>, and [Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> give, depending
on the pH value, two new large polyoxometalate complexes: i.e., [(Ī³-Se<sub>2</sub>W<sub>14</sub>O<sub>52</sub>)<sub>3</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>)<sub>6</sub>]<sup>24ā</sup> (<b>1</b>) isolated at
pH 3.5 and [(Ī³-Se<sub>2</sub>W<sub>14</sub>O<sub>52</sub>)<sub>4</sub>Ā(WO<sub>3</sub>(H<sub>2</sub>O))<sub>8</sub>Ā(W<sub>2</sub>O<sub>5</sub>)<sub>2</sub>Ā(W<sub>4</sub>O<sub>12</sub>)<sub>2</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(H<sub>2</sub>O)<sub>2</sub>)<sub>4</sub>Ā(Mo<sub>2</sub>O<sub>2</sub>(Ī¼-S)<sub>2</sub>Ā(SeO<sub>3</sub>))<sub>4</sub>]<sup>36ā</sup> (<b>2</b>) isolated at pH 2.
Both compounds were characterized in the solid state by single-crystal
X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in
solution by ESI-MS and NMR
Cd<sup>2+</sup> Complexation with P(CH<sub>2</sub>OH)<sub>3</sub>, OP(CH<sub>2</sub>OH)<sub>3</sub>, and (HOCH<sub>2</sub>)<sub>2</sub>PO<sub>2</sub><sup>ā</sup>: Coordination in Solution and Coordination Polymers
The coordination of Cd<sup>2+</sup> with PĀ(CH<sub>2</sub>OH)<sub>3</sub> (THP) in methanol was followed by <sup>31</sup>P
and <sup>111</sup>Cd NMR techniques. A cadmium-to-phosphine coordination
ratio
of 1:3 has been established, and effective kinetic parameters have
been calculated. Air oxidation of THP in the presence of CdCl<sub>2</sub> at room temperature produces coordination polymer <sup>3</sup><sub>ā</sub>[Cd<sub>3</sub>Cl<sub>6</sub>(OPĀ(CH<sub>2</sub>OH)<sub>3</sub>)<sub>2</sub>] (<b>1</b>). The same oxidation
reaction at 70 Ā°C gives another coordination polymer, <sub>ā</sub>[CdCl<sub>2</sub>(OPĀ(CH<sub>2</sub>OH)<sub>3</sub>)] (<b>2</b>). Complexes <b>1</b> and <b>2</b> are the first structurally
characterized complexes featuring OPĀ(CH<sub>2</sub>OH)<sub>3</sub> as a ligand that acts as a linker between Cd atoms. The addition
of NaBPh<sub>4</sub> to the reaction mixture gives coordination polymer <sub>ā</sub>[Na<sub>2</sub>CdCl<sub>2</sub>(O<sub>2</sub>PĀ(CH<sub>2</sub>OH)<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>]
(<b>3</b>) with (HOCH<sub>2</sub>)<sub>2</sub>PO<sub>2</sub><sup>ā</sup> as the ligand. Coordination polymers <b>1</b>ā<b>3</b> have been characterized by X-ray analysis,
elemental analysis, and IR spectroscopy
Synthesis and Characterization of [(OH)TeNb<sub>5</sub>O<sub>18</sub>]<sup>6ā</sup> in Water Solution, Comparison with [Nb<sub>6</sub>O<sub>19</sub>]<sup>8ā</sup>
Reaction
of [Nb<sub>6</sub>O<sub>19</sub>]<sup>8ā</sup> with
H<sub>6</sub>TeO<sub>6</sub> in water gives telluropentaniobate [(OH)ĀTeĀNb<sub>5</sub>O<sub>18</sub>]<sup>6ā</sup> (<b>1</b>) as single
product, which was isolated as Na<sup>+</sup> and mixed Na<sup>+</sup>/K<sup>+</sup> salts. Crystal structures were determined for Na<sub>6</sub>[(OH)ĀTeNb<sub>5</sub>O<sub>18</sub>]Ā·15H<sub>2</sub>O (<b>Na</b><sub><b>6</b></sub><b>-1</b>) and K<sub>6</sub>NaĀ[Nb<sub>5.5</sub>Ā{TeĀ(OH)}<sub>0.5</sub>O<sub>18.5</sub>]Ā·26H<sub>2</sub>O (<b>K</b><sub><b>6</b></sub><b>Na-1</b>). Formation of <b>1</b> was monitored with electrospray
ionization mass spectrometry (ESI-MS) and <sup>125</sup>Te NMR techniques.
Capillary electrophoresis was used to calculate electrophoretic mobilities
and radii of the anionic species in solutions of [(OH)ĀTeĀNb<sub>5</sub>O<sub>18</sub>]<sup>6ā</sup> and [Nb<sub>6</sub>O<sub>19</sub>]<sup>8ā</sup> in borate buffer. No condensation or
degradation products were detected. Reactions of <b>1</b> with
{Cp*Rh}<sup>2+</sup> sources gives 1:1 and 2:1 hybrid polyoxometalate,
which are present in solution as a mixture of isomers, as detected
by <sup>125</sup>Te NMR. The isomerism is related to various possibilities
of coordination of {Cp*Rh}<sup>2+</sup> to different {M<sub>3</sub>O<sub>3</sub>} faces, relative to the unique Te atom. According to
ESI-MS experiments in water and methanol, rapid redistribution of
the organometallic fragments between the 1:1 and 2:1 complexes takes
place. The 1:1 complexes are more stable in water, while 2:1 complexes
dominate in methanol. X-ray structural analysis of the crystals isolated
from 2:1 reaction mixture allowed identification of Na<sub>3</sub>[{Cp*Rh}<sub>2</sub>ĀTeNb<sub>5</sub>O<sub>19</sub>]Ā·24H<sub>2</sub>O (<b>Cp*</b><sub><b>2</b></sub><b>Rh</b><sub><b>2</b></sub><b>-1</b>) with two {Cp*Rh}<sup>2+</sup> fragments capping the opposing faces of the Lindqvist anion
Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo<sub>3</sub>CuS<sub>4</sub> Clusters with 4,4ā²-Di-<i>tert</i>-butyl-2,2ā²-bipyridine
Treatment
of the triangular [Mo<sub>3</sub>S<sub>4</sub>Cl<sub>3</sub>(dbbpy)<sub>3</sub>]Cl cluster ([<b>1</b>]ĀCl) with CuCl
produces a novel tetrametallic cuboidal cluster [Mo<sub>3</sub>(CuCl)ĀS<sub>4</sub>Cl<sub>3</sub>(dbbpy)<sub>3</sub>]Ā[CuCl<sub>2</sub>] ([<b>2</b>]Ā[CuCl<sub>2</sub>]), whose crystal structure was determined
by X-ray diffraction (dbbpy = 4,4ā²-di-<i>tert</i>-butyl-2,2ā²-bipyridine). This species, which contains two
distinct types of CuĀ(I), is the first example of a diimine-functionalized
heterometallic M<sub>3</sub>Mā²S<sub>4</sub> cluster. Kinetics
studies on both the formation of the cubane from the parent trinuclear
cluster and its dissociation after treatment with halides, supported
by NMR, electrospray ionization mass spectrometry, cyclic voltammetry,
and density functional theory calculations, are provided. On the one
hand, the results indicate that addition of CuĀ(I) to [<b>1</b>]<sup>+</sup> is so fast that its kinetics can be monitored only
by cryo-stopped flow at ā85 Ā°C. On the other hand, the
release of the CuCl unit in [<b>2</b>]<sup>+</sup> is also a
fast process, which is unexpectedly assisted by the CuCl<sub>2</sub><sup>ā</sup> counteranion in a process triggered by halide
(X<sup>ā</sup>) anions. The whole set of results provide a
detailed picture of the assemblyādisassembly processes in this
kind of cluster. Interconversion between trinuclear M<sub>3</sub>S<sub>4</sub> clusters and their heterometallic M<sub>3</sub>Mā²S<sub>4</sub> derivatives can be a fast process occurring readily under
the conditions employed during reactivity and catalytic studies, so
their occurrence is a possibility that must be taken into account
in future studies
Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo<sub>3</sub>CuS<sub>4</sub> Clusters with 4,4ā²-Di-<i>tert</i>-butyl-2,2ā²-bipyridine
Treatment
of the triangular [Mo<sub>3</sub>S<sub>4</sub>Cl<sub>3</sub>(dbbpy)<sub>3</sub>]Cl cluster ([<b>1</b>]ĀCl) with CuCl
produces a novel tetrametallic cuboidal cluster [Mo<sub>3</sub>(CuCl)ĀS<sub>4</sub>Cl<sub>3</sub>(dbbpy)<sub>3</sub>]Ā[CuCl<sub>2</sub>] ([<b>2</b>]Ā[CuCl<sub>2</sub>]), whose crystal structure was determined
by X-ray diffraction (dbbpy = 4,4ā²-di-<i>tert</i>-butyl-2,2ā²-bipyridine). This species, which contains two
distinct types of CuĀ(I), is the first example of a diimine-functionalized
heterometallic M<sub>3</sub>Mā²S<sub>4</sub> cluster. Kinetics
studies on both the formation of the cubane from the parent trinuclear
cluster and its dissociation after treatment with halides, supported
by NMR, electrospray ionization mass spectrometry, cyclic voltammetry,
and density functional theory calculations, are provided. On the one
hand, the results indicate that addition of CuĀ(I) to [<b>1</b>]<sup>+</sup> is so fast that its kinetics can be monitored only
by cryo-stopped flow at ā85 Ā°C. On the other hand, the
release of the CuCl unit in [<b>2</b>]<sup>+</sup> is also a
fast process, which is unexpectedly assisted by the CuCl<sub>2</sub><sup>ā</sup> counteranion in a process triggered by halide
(X<sup>ā</sup>) anions. The whole set of results provide a
detailed picture of the assemblyādisassembly processes in this
kind of cluster. Interconversion between trinuclear M<sub>3</sub>S<sub>4</sub> clusters and their heterometallic M<sub>3</sub>Mā²S<sub>4</sub> derivatives can be a fast process occurring readily under
the conditions employed during reactivity and catalytic studies, so
their occurrence is a possibility that must be taken into account
in future studies
Nonconventional Three-Component Hierarchical HostāGuest Assembly Based on Mo-Blue Ring-Shaped Giant Anion, Ī³āCyclodextrin, and Dawson-type Polyoxometalate
In
this communication, we report on a noteworthy hybrid supramolecular
assembly built from three functional components hierarchically organized
through noncovalent interactions. The one-pot synthesis procedure
leads to the formation of large Mo-blue ring-shaped anion {Mo<sub>154</sub>}, which contains the supramolecular adduct based on the
symmetric encapsulation of the Dawson-type [P<sub>2</sub>W<sub>18</sub>O<sub>62</sub>]<sup>6ā</sup> anion by two Ī³-cyclodextrin
units. Such a nanoscopic onion-like structure, noted [P<sub>2</sub>W<sub>18</sub>O<sub>62</sub>]@2Ī³-CD@{Mo<sub>154</sub>} has
been characterized by single-crystal X-ray diffraction, thus demonstrating
the capability of the giant inorganic torus to develop relevant supramolecular
chemistry, probing the strong affinity of the inner and outer faces
of the Ī³-CD for the polyoxometalate surfaces. Furthermore, interactions
and behavior in solution have been studied by multinuclear NMR spectroscopy,
which supports specific interactions between Ī³-CD and POM units.
Finally, the formation of this three-component hybrid assembly from
one-pot procedure, in water and using nearly stoichiometric conditions,
is discussed in terms of the driving forces orchestrating this highly
efficient multilevel recognition process