79 research outputs found
Iron(II) Complexes Supported by Sulfonamido Tripodal Ligands: Endogenous versus Exogenous Substrate Oxidation
High-valent
iron species are known to act as powerful oxidants in both natural
and synthetic systems. While biological enzymes have evolved to prevent
self-oxidation by these highly reactive species, development of organic
ligand frameworks that are capable of supporting a high-valent iron
center remains a challenge in synthetic chemistry. We describe here
the reactivity of an FeÂ(II) complex that is supported by a tripodal
sulfonamide ligand with both dioxygen and an oxygen-atom transfer
reagent, 4-methylmorpholine-<i>N</i>-oxide (NMO). An FeÂ(III)âhydroxide
complex is obtained from reaction with dioxygen, while NMO gives
an FeÂ(III)âalkoxide product resulting from activation of a
CâH bond of the ligand. Inclusion of Ca<sup>2+</sup> ions in
the reaction with NMO prevented this ligand activation and resulted
in isolation of an FeÂ(III)âhydroxide complex in which the Ca<sup>2+</sup> ion is coordinated to the tripodal sulfonamide ligand and
the hydroxo ligand. Modification of the ligand allowed the FeÂ(III)âhydroxide
complex to be isolated from NMO in the absence of Ca<sup>2+</sup> ions,
and a CâH bond of an external substrate could be activated
during the reaction. This study highlights the importance of robust
ligand design in the development of synthetic catalysts that utilize
a high-valent iron center
Solvent-Free Organometallic Reactivity: Synthesis of Hydride and Carboxylate Complexes of Uranium and Yttrium from Gas/Solid Reactions
Gas/solid
reactions involving H<sub>2</sub> and CO<sub>2</sub> with
the metallocenes (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(allyl)<sub>2</sub> as solids in the absence of solvent provide an improved method
to make organouranium hydride and carboxylate products. Decomposition
products that can form in solution from the reactive hydrides can
be avoided by this method, and this approach can also provide intermediates
too reactive to isolate in some solution reactions. In contrast to
the variable nature of the hydrogenolysis reaction of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> in toluene that forms
byproducts along with the mixture of [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH<sub>2</sub>]<sub>2</sub> and [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH]<sub>2</sub>, a byproduct-free hydrogenolysis
occurs when (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> in the solid state is treated with H<sub>2</sub> gas to form predominantly
[(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH<sub>2</sub>]<sub>2</sub>. H<sub>2</sub> reacts with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(C<sub>3</sub>H<sub>5</sub>)<sub>2</sub> and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(C<sub>3</sub>H<sub>5</sub>) similarly.
The reaction of CO<sub>2</sub> (80 psi) with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> forms the monocarboxylate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(O<sub>2</sub>CCH<sub>3</sub>-Îș<sup>2</sup><i>O</i>,<i>O</i>âČ)ÂMe, in contrast
to the solution reaction that forms the diacetate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(O<sub>2</sub>CCH<sub>3</sub>-Îș<sup>2</sup><i>O</i>,<i>O</i>âČ)<sub>2</sub> in minutes.
The reaction of H<sub>2</sub> with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YÂ(C<sub>3</sub>H<sub>5</sub>) provided (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YÂ(ÎŒ-H)ÂYHÂ(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub> without the decomposition products that it forms in
solution such that single crystals suitable for X-ray diffraction
could be isolated for the first time
Solvent-Free Organometallic Reactivity: Synthesis of Hydride and Carboxylate Complexes of Uranium and Yttrium from Gas/Solid Reactions
Gas/solid
reactions involving H<sub>2</sub> and CO<sub>2</sub> with
the metallocenes (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(allyl)<sub>2</sub> as solids in the absence of solvent provide an improved method
to make organouranium hydride and carboxylate products. Decomposition
products that can form in solution from the reactive hydrides can
be avoided by this method, and this approach can also provide intermediates
too reactive to isolate in some solution reactions. In contrast to
the variable nature of the hydrogenolysis reaction of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> in toluene that forms
byproducts along with the mixture of [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH<sub>2</sub>]<sub>2</sub> and [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH]<sub>2</sub>, a byproduct-free hydrogenolysis
occurs when (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> in the solid state is treated with H<sub>2</sub> gas to form predominantly
[(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UH<sub>2</sub>]<sub>2</sub>. H<sub>2</sub> reacts with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(C<sub>3</sub>H<sub>5</sub>)<sub>2</sub> and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(C<sub>3</sub>H<sub>5</sub>) similarly.
The reaction of CO<sub>2</sub> (80 psi) with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UMe<sub>2</sub> forms the monocarboxylate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(O<sub>2</sub>CCH<sub>3</sub>-Îș<sup>2</sup><i>O</i>,<i>O</i>âČ)ÂMe, in contrast
to the solution reaction that forms the diacetate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(O<sub>2</sub>CCH<sub>3</sub>-Îș<sup>2</sup><i>O</i>,<i>O</i>âČ)<sub>2</sub> in minutes.
The reaction of H<sub>2</sub> with solid (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YÂ(C<sub>3</sub>H<sub>5</sub>) provided (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>YÂ(ÎŒ-H)ÂYHÂ(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub> without the decomposition products that it forms in
solution such that single crystals suitable for X-ray diffraction
could be isolated for the first time
Synthesis and CO<sub>2</sub> Insertion Reactivity of Allyluranium Metallocene Complexes
The U<sup>4+</sup> metallocene allyl chloride complexes
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[η<sup>3</sup>-CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]Cl (R = H, Me) can be synthesized by reaction
of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UCl<sub>2</sub> with 1
equiv of the corresponding allyl Grignard reagents, [CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]ÂMgCl, in hydrocarbon solvents. BisÂ(allyl)Âuranium
complexes can also be obtained in this manner using 2 equiv of the
corresponding allyl Grignard, and X-ray crystallographic studies reveal
the presence of both η<sup>3</sup>- and η<sup>1</sup>-allyl
ligands: (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[η<sup>3</sup>-CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]Â[η<sup>1</sup>-CH<sub>2</sub>CÂ(R)î»CH<sub>2</sub>]. Sodium amalgam reduction of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[η<sup>3</sup>-CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]Cl generates the U<sup>3+</sup> metallocene allyl complexes
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[η<sup>3</sup>-CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]. Carbon dioxide reacts with the U<sup>4+</sup> allyl complexes to form the UâC insertion products
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[Îș<sup>2</sup><i>O</i>,<i>O</i>âČ-O<sub>2</sub>CCH<sub>2</sub>CHî»CH<sub>2</sub>]<sub>2â<i>x</i></sub>Cl<sub>x</sub> (<i>x</i> = 0, 1). The dicarboxylate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[Îș<sup>2</sup><i>O</i>,<i>O</i>âČ-O<sub>2</sub>CCH<sub>2</sub>CHî»CH<sub>2</sub>]<sub>2</sub>, which has a 171.98(5)° OâUâO
angle, reacts with Me<sub>3</sub>SiCl to regenerate (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UCl<sub>2</sub> and liberate Me<sub>3</sub>SiOCÂ(O)ÂCH<sub>2</sub>CHî»CH<sub>2</sub>
Reactivity of U<sup>3+</sup> Metallocene Allyl Complexes Leads to a Nanometer-Sized Uranium Carbonate, [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>6</sub>(ÎŒâÎș<sup>1</sup>:Îș<sup>2</sup>âCO<sub>3</sub>)<sub>6</sub>
The U<sup>3+</sup> allyl complexes
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] (R = H, Me) display
three different types of reactivity, as exemplified by reactions with
PhNî»NPh, cyclooctatetraene, and CO<sub>2</sub>. Two equivalents
of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] effect a four-electron reduction of PhNî»NPh to form
the bisÂ(imido) complex (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(î»NPh)<sub>2</sub> and the bisÂ(allyl) species (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]<sub>2</sub>. Two-electron
reduction of C<sub>8</sub>H<sub>8</sub> occurs to form (C<sub>5</sub>Me<sub>5</sub>)Â(C<sub>8</sub>H<sub>8</sub>)ÂUÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] products that contain only one cyclopentadienyl ring per
metal. With CO<sub>2</sub> at 80 psi, both reduction and insertion
occur. A hexametallic uranium carbonate, [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>6</sub>(ÎŒ-Îș<sup>1</sup>:Îș<sup>2</sup>-CO<sub>3</sub>)<sub>6</sub>, is isolated as well as the bisÂ(carboxylate)
complexes (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[Îș<sup>2</sup>-<i>O</i>,<i>O</i>âČ-O<sub>2</sub>CCH<sub>2</sub>CÂ(R)î»CH<sub>2</sub>]<sub>2</sub>. The polymetallic
carbonate complex can also be synthesized from [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>2</sub>(ÎŒ-η<sup>6</sup>:η<sup>6</sup>-C<sub>6</sub>H<sub>6</sub>) and [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]Â[(ÎŒ-Ph)<sub>2</sub>BPh<sub>2</sub>] and CO<sub>2</sub>
Reactivity of U<sup>3+</sup> Metallocene Allyl Complexes Leads to a Nanometer-Sized Uranium Carbonate, [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>6</sub>(ÎŒâÎș<sup>1</sup>:Îș<sup>2</sup>âCO<sub>3</sub>)<sub>6</sub>
The U<sup>3+</sup> allyl complexes
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] (R = H, Me) display
three different types of reactivity, as exemplified by reactions with
PhNî»NPh, cyclooctatetraene, and CO<sub>2</sub>. Two equivalents
of (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] effect a four-electron reduction of PhNî»NPh to form
the bisÂ(imido) complex (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ(î»NPh)<sub>2</sub> and the bisÂ(allyl) species (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>]<sub>2</sub>. Two-electron
reduction of C<sub>8</sub>H<sub>8</sub> occurs to form (C<sub>5</sub>Me<sub>5</sub>)Â(C<sub>8</sub>H<sub>8</sub>)ÂUÂ[CH<sub>2</sub>CÂ(R)ÂCH<sub>2</sub>] products that contain only one cyclopentadienyl ring per
metal. With CO<sub>2</sub> at 80 psi, both reduction and insertion
occur. A hexametallic uranium carbonate, [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>6</sub>(ÎŒ-Îș<sup>1</sup>:Îș<sup>2</sup>-CO<sub>3</sub>)<sub>6</sub>, is isolated as well as the bisÂ(carboxylate)
complexes (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[Îș<sup>2</sup>-<i>O</i>,<i>O</i>âČ-O<sub>2</sub>CCH<sub>2</sub>CÂ(R)î»CH<sub>2</sub>]<sub>2</sub>. The polymetallic
carbonate complex can also be synthesized from [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]<sub>2</sub>(ÎŒ-η<sup>6</sup>:η<sup>6</sup>-C<sub>6</sub>H<sub>6</sub>) and [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>U]Â[(ÎŒ-Ph)<sub>2</sub>BPh<sub>2</sub>] and CO<sub>2</sub>
Modulating the Primary and Secondary Coordination Spheres within a Series of Co<sup>II</sup>îžOH Complexes
The interplay between
the primary and secondary coordination spheres is crucial to determining
the properties of transition metal complexes. To examine these effects,
a series of trigonal bipyramidal CoâOH complexes have been
prepared with tripodal ligands that control both coordination spheres.
The ligands contain a combination of either urea or sulfonamide groups
that control the primary coordination sphere through anionic donors
in the trigonal plane and the secondary coordination sphere through
intramolecular hydrogen bonds. Variations in the anion donor strengths
were evaluated using electronic absorbance spectroscopy and a qualitative
ligand field analysis to find that deprotonated urea donors are stronger
field ligands than deprotonated sulfonamides. Structural variations
were found in the Co<sup>II</sup>âO bond lengths that range
from 1.953(4) to 2.051(3) Ă
; this range in bond lengths were
attributed to the differences in the intramolecular hydrogen bonds
that surround the hydroxido ligand. A similar trend was observed between
the hydrogen bonding networks and the vibrations of the OâH
bonds. Attempts to isolate the corresponding Co<sup>III</sup>âOH
complexes were hampered by their instability at room temperature
Synthesis and Characterization of a Redox-Active Bis(thiophenolato)amide Ligand, [SNS]<sup>3â</sup>, and the Homoleptic Tungsten Complexes, W[SNS]<sub>2</sub> and W[ONO]<sub>2</sub>
A new tridentate redox-active ligand platform, derived
from bisÂ(2-mercapto-<i>p</i>-tolyl)Âamine, [SNS<sup>cat</sup>]ÂH<sub>3</sub>, has been prepared in high yields by a four-step procedure
starting from commericially available bisÂ(<i>p</i>-tolyl)Âamine.
The redox-active pincer-type ligand has been coordinated to tungsten
to afford the six-coordinate, homoleptic complex WÂ[SNS]<sub>2</sub>. To benchmark the redox behavior of the [SNS] ligand, the analogous
tungsten complex of the well-known redox-active bisÂ(3,5-di-<i>tert</i>-butylphenolato)Âamide ligand, WÂ[ONO]<sub>2</sub>, also
has been prepared. Both complexes show two reversible reductions and
two partially reversible oxidations. Structural, spectroscopic, and
electrochemical data all indicate that WÂ[ONO]<sub>2</sub> is best
described as a tungstenÂ(VI) metal center coordinated to two [ONO<sup>cat</sup>]<sup>3â</sup> ligands. In contrast, experimental
data suggests a higher degree of SâW Ï donation, giving
the WÂ[SNS]<sub>2</sub> complex non-innocent electronic character that
can be described as a tungstenÂ(IV) metal center coordinated to two
[SNS<sup>sq</sup>]<sup>2â</sup> ligands
Expanding Yttrium Bis(trimethylsilylamide) Chemistry Through the Reaction Chemistry of (N<sub>2</sub>)<sup>2â</sup>, (N<sub>2</sub>)<sup>3â</sup>, and (NO)<sup>2â</sup> Complexes
The reaction chemistry of the side-on bound (N<sub>2</sub>)<sup>2â</sup>, (N<sub>2</sub>)<sup>3â</sup>, and (NO)<sup>2â</sup> complexes of the [(R<sub>2</sub>N)<sub>2</sub>Y]<sup>+</sup> cation (R = SiMe<sub>3</sub>), namely, [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY]<sub>2</sub>(<i>ÎŒ</i>-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>), <b>1</b>, [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY]<sub>2</sub>(<i>ÎŒ</i>-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>)ÂK, <b>2</b>, and
[(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY]<sub>2</sub>(<i>ÎŒ</i>-η<sup>2</sup>:η<sup>2</sup>-NO), <b>3</b>, with
oxidizing agents has been explored to search for other (E<sub>2</sub>)<sup><i>n</i>â</sup>, (E = N, O), species that
can be stabilized by this cation. This has led to the first examples
for the [(R<sub>2</sub>N)<sub>2</sub>Y]<sup>+</sup> cation of two
fundamental classes of [(monoanion)<sub>2</sub>Ln]<sup>+</sup> rare
earth systems (Ln = Sc, Y, lanthanides), namely, oxide complexes
and the tetraphenylborate salt. In addition, an unusually high yield reaction
with dioxygen was found to give a peroxide complex that completes
the (N<sub>2</sub>)<sup>2â</sup>, (NO)<sup>2â</sup>,
(O<sub>2</sub>)<sup>2â</sup> series with <b>1</b> and <b>3</b>. Specifically, the (<i><i>ÎŒ</i>-</i>O)<sup>2â</sup> oxide-bridged bimetallic complex, [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY}<sub>2</sub>(<i><i>ÎŒ</i>-</i>O), <b>4</b>, is obtained as a byproduct from reactions
of either the (N<sub>2</sub>)<sup>2â</sup> complex, <b>1</b>, or the (N<sub>2</sub>)<sup>3â</sup> complex, <b>2</b>, with NO, while the oxide formed from <b>2</b> with N<sub>2</sub>O is a polymeric species incorporating potassium, {[(R<sub>2</sub>N)<sub>2</sub>Y]<sub>2</sub>(<i><i>ÎŒ</i>-</i>O)<sub>2</sub>K<sub>2</sub>(<i><i>ÎŒ</i>-</i>C<sub>7</sub>H<sub>8</sub>)}<sub><i>n</i></sub>, <b>5</b>. Reaction of <b>1</b> with 1 atm of O<sub>2</sub> generates the (O<sub>2</sub>)<sup>2â</sup> bridging
side-on peroxide [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY]<sub>2</sub>(<i>ÎŒ</i>-η<sup>2</sup>:η<sup>2</sup>-O<sub>2</sub>), <b>6</b>. The OâO bond in <b>6</b> is cleaved
by KC<sub>8</sub> to provide an alternative synthetic route to <b>5</b>. Attempts to oxidize the (NO)<sup>2â</sup> complex, <b>3</b>, with AgBPh<sub>4</sub> led to the isolation of the tetraphenylborate
complex, [(R<sub>2</sub>N)<sub>2</sub>YÂ(THF)<sub>3</sub>]Â[BPh<sub>4</sub>], <b>7</b>, that was also synthesized from <b>1</b> and AgBPh<sub>4</sub>. Oxidation of the (N<sub>2</sub>)<sup>2â</sup> complex, <b>1</b>, with the radical trap (2,2,6,6-tetramethylpiperidin-1-yl)Âoxyl,
TEMPO, generates the (TEMPO)<sup>â</sup> anion complex, (R<sub>2</sub>N)<sub>2</sub>(THF)ÂYÂ(η<sup>2</sup>-ONC<sub>5</sub>H<sub>6</sub>Me<sub>4</sub>), <b>8</b>
Cocrystallization of (ÎŒâS<sub>2</sub>)<sup>2â</sup> and (ÎŒ-S)<sup>2â</sup> and Formation of an [η<sup>2</sup>âS<sub>3</sub>N(SiMe<sub>3</sub>)<sub>2</sub>] Ligand from Chalcogen Reduction by (N<sub>2</sub>)<sup>2â</sup> in a Bimetallic Yttrium Amide Complex
The reactivity of the (N<sub>2</sub>)<sup>2â</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(ÎŒ-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>) (<b>1</b>) with sulfur and selenium
has been studied to explore the special reductive chemistry of this
complex and to expand the variety of bimetallic rare-earth amide complexes.
Complex <b>1</b> reacts with elemental sulfur to form a mixture
of compounds, <b>2</b>, that is the first example of cocrystallized
complexes of (S<sub>2</sub>)<sup>2â</sup> and S<sup>2â</sup> ligands. The crystals of <b>2</b> contain both the (ÎŒ-S<sub>2</sub>)<sup>2â</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(ÎŒ-η<sup>2</sup>:η<sup>2</sup>-S<sub>2</sub>) (<b>3</b>) and the (ÎŒ-S)<sup>2â</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(ÎŒ-S) (<b>4</b>), respectively. Modeling of the
crystal data of <b>2</b> shows a 9:1 ratio of <b>3</b>:<b>4</b> in the crystals of <b>2</b> obtained from solutions
that have 1:1 to 4:1 ratios of <b>3</b>/<b>4</b> by <sup>1</sup>H NMR spectroscopy. The addition of KC<sub>8</sub> to samples
of <b>2</b> allows for the isolation of single crystals of <b>4</b>. The [S<sub>3</sub>NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sup>â</sup> ligand was isolated for the first time in crystals
of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ[η<sup>2</sup>-S<sub>3</sub>NÂ(SiMe<sub>3</sub>)<sub>2</sub>]Â(THF) (<b>5</b>), obtained from the mother liquor of <b>2</b>. In contrast
to the sulfur chemistry, the (ÎŒ-Se<sub>2</sub>)<sup>2â</sup> analogue of <b>3</b>, namely, {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(ÎŒ-η<sup>2</sup>:η<sup>2</sup>-Se<sub>2</sub>) (<b>6</b>), can be cleanly synthesized
in good yield by reacting <b>1</b>, with elemental selenium.
The (ÎŒ-Se)<sup>2â</sup> analogue of <b>4</b>, namely,
{[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(ÎŒ-Se)
(<b>7</b>), was synthesized from Ph<sub>3</sub>PSe
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