80 research outputs found
<sup>29</sup>Si NMR Spectra of Silicon-Containing Uranium Complexes
No full text<sup>29</sup>Si NMR spectra have been recorded for a series of
uranium complexes containing silicon, and the data have been combined
with results in the literature to determine if any trends exist between
chemical shift and structure, ligand type, or oxidation state. Data
on 52 paramagnetic inorganic and organometallic uranium complexes
are presented. The survey reveals that, although there is some overlap
in the range of shifts of U<sup>4+</sup> complexes versus U<sup>3+</sup> complexes, in general U<sup>3+</sup> species have shifts more negative
than those of their U<sup>4+</sup> analogues. The single U<sup>2+</sup> example has the most negative shift of all at −322 ppm at
170 K. With only a few exceptions, U<sup>4+</sup> complexes have shifts
between 0 and −150 ppm (vs SiMe<sub>4</sub>), whereas U<sup>3+</sup> complexes resonate between −120 and −250 ppm.
The small data set on U<sup>5+</sup> species exhibits a broad 250
ppm range centered near 40 ppm. The data also show that aromatic ligands
such as cyclopentadienide, cyclooctatetraenide, and the pentalene
dianion exhibit chemical shifts less negative than those of other
types of ligands
Solvent-Free Organometallic Reactivity: Synthesis of Hydride and Carboxylate Complexes of Uranium and Yttrium from Gas/Solid Reactions
No full textGas/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>-κ<sup>2</sup><i>O</i>,<i>O</i>′)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>-κ<sup>2</sup><i>O</i>,<i>O</i>′)<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(μ-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
No full textGas/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>-κ<sup>2</sup><i>O</i>,<i>O</i>′)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>-κ<sup>2</sup><i>O</i>,<i>O</i>′)<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(μ-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
No full textThe 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 U–C insertion products
(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>UÂ[κ<sup>2</sup><i>O</i>,<i>O</i>′-O<sub>2</sub>CCH<sub>2</sub>CHî—»CH<sub>2</sub>]<sub>2–<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[κ<sup>2</sup><i>O</i>,<i>O</i>′-O<sub>2</sub>CCH<sub>2</sub>CHî—»CH<sub>2</sub>]<sub>2</sub>, which has a 171.98(5)° O–U–O
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>(μ‑κ<sup>1</sup>:κ<sup>2</sup>‑CO<sub>3</sub>)<sub>6</sub>
No full textThe 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>(μ-κ<sup>1</sup>:κ<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[κ<sup>2</sup>-<i>O</i>,<i>O</i>′-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>(μ-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[(μ-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>(μ‑κ<sup>1</sup>:κ<sup>2</sup>‑CO<sub>3</sub>)<sub>6</sub>
No full textThe 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>(μ-κ<sup>1</sup>:κ<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[κ<sup>2</sup>-<i>O</i>,<i>O</i>′-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>(μ-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[(μ-Ph)<sub>2</sub>BPh<sub>2</sub>] and CO<sub>2</sub>
Expanding Yttrium Bis(trimethylsilylamide) Chemistry Through the Reaction Chemistry of (N<sub>2</sub>)<sup>2–</sup>, (N<sub>2</sub>)<sup>3–</sup>, and (NO)<sup>2–</sup> Complexes
No full textThe reaction chemistry of the side-on bound (N<sub>2</sub>)<sup>2–</sup>, (N<sub>2</sub>)<sup>3–</sup>, and (NO)<sup>2–</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>μ</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>μ</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>μ</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>−</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>2–</sup>, (NO)<sup>2–</sup>,
(O<sub>2</sub>)<sup>2–</sup> series with <b>1</b> and <b>3</b>. Specifically, the (<i><i>μ</i>-</i>O)<sup>2–</sup> oxide-bridged bimetallic complex, [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY}<sub>2</sub>(<i><i>μ</i>-</i>O), <b>4</b>, is obtained as a byproduct from reactions
of either the (N<sub>2</sub>)<sup>2–</sup> complex, <b>1</b>, or the (N<sub>2</sub>)<sup>3–</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>μ</i>-</i>O)<sub>2</sub>K<sub>2</sub>(<i><i>μ</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>2–</sup> bridging
side-on peroxide [(R<sub>2</sub>N)<sub>2</sub>(THF)ÂY]<sub>2</sub>(<i>μ</i>-η<sup>2</sup>:η<sup>2</sup>-O<sub>2</sub>), <b>6</b>. The O–O 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>2–</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>2–</sup> complex, <b>1</b>, with the radical trap (2,2,6,6-tetramethylpiperidin-1-yl)Âoxyl,
TEMPO, generates the (TEMPO)<sup>−</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>
Synthesis and Structure of Bis- and Tris-Benzyl Bismuth Complexes
No full textThe
first crystallographic characterization of bismuth complexes
containing benzyl ligands is reported. The NCN pincer ligand complex,
Ar′BiCl<sub>2</sub> [Ar′ = 2,6-(Me<sub>2</sub>NCH<sub>2</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>], reacts with (PhCH<sub>2</sub>)ÂMgCl to form Ar′BiÂ(η<sup>1</sup>-CH<sub>2</sub>Ph)<sub>2</sub> in high yield. X-ray crystallography and spectroscopic
studies confirm η<sup>1</sup>-bonding of the benzyl ligands
in Ar′BiÂ(η<sup>1</sup>-CH<sub>2</sub>Ph)<sub>2</sub> as
well as in the homoleptic BiÂ(η<sup>1</sup>-CH<sub>2</sub>Ph)<sub>3</sub>
Cocrystallization of (μ‑S<sub>2</sub>)<sup>2–</sup> and (μ-S)<sup>2–</sup> and Formation of an [η<sup>2</sup>‑S<sub>3</sub>N(SiMe<sub>3</sub>)<sub>2</sub>] Ligand from Chalcogen Reduction by (N<sub>2</sub>)<sup>2–</sup> in a Bimetallic Yttrium Amide Complex
No full textThe reactivity of the (N<sub>2</sub>)<sup>2–</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(μ-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>2–</sup> and S<sup>2–</sup> ligands. The crystals of <b>2</b> contain both the (μ-S<sub>2</sub>)<sup>2–</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(μ-η<sup>2</sup>:η<sup>2</sup>-S<sub>2</sub>) (<b>3</b>) and the (μ-S)<sup>2–</sup> complex {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(μ-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>−</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 (μ-Se<sub>2</sub>)<sup>2–</sup> analogue of <b>3</b>, namely, {[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(μ-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 (μ-Se)<sup>2–</sup> analogue of <b>4</b>, namely,
{[(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>2</sub>YÂ(THF)}<sub>2</sub>(μ-Se)
(<b>7</b>), was synthesized from Ph<sub>3</sub>PSe
Reactivity of Organothorium Complexes with TEMPO
No full textReactions
of the 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO)
with thorium metallocenes have been examined to investigate both the
radical reaction patterns for organothorium complexes and the coordination
chemistry of TEMPO with thorium. (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThMe<sub>2</sub> reacts with 2 equiv of
TEMPO to generate 1-methoxy-2,2,6,6-tetramethylpiperidine (Me-TEMPO)
and (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThMeÂ(η<sup>1</sup>-TEMPO), which contains a TEMPO<sup>–</sup> anion coordinated
to thorium through oxygen only. (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThÂ(η<sup>1</sup>-C<sub>3</sub>H<sub>5</sub>)Â(η<sup>3</sup>-C<sub>3</sub>H<sub>5</sub>), synthesized
from (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThBr<sub>2</sub> and (C<sub>3</sub>H<sub>5</sub>)ÂMgBr, reacts with
2 equiv of TEMPO to form 1-(2-propen-1-yloxy)-2,2,6,6-tetramethylpiperidine
(allyl-TEMPO) and (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThÂ(η<sup>1</sup>-C<sub>3</sub>H<sub>5</sub>)Â(η<sup>1</sup>-TEMPO). Although bisÂ(TEMPO) metallocenes were not obtained
in these reactions, the methyl group in (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThMeÂ(η<sup>1</sup>-TEMPO)
is reactive with 1 equiv of CuBr to form (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThBrÂ(η<sup>1</sup>-TEMPO).
The bisÂ(TEMPO) metallocene (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThÂ(η<sup>1</sup>-TEMPO)<sub>2</sub> is
accessible in the reaction of [(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThH<sub>2</sub>]<sub>2</sub> with 4 equiv of
TEMPO. In contrast, (η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>ThBr<sub>2</sub> reacts with 2 equiv of TEMPO by loss
of C<sub>5</sub>Me<sub>5</sub> to form (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub> and (η<sup>2</sup>-TEMPO)<sub>2</sub>ThBr<sub>2</sub>, in which the TEMPO<sup>–</sup> anions bind through
oxygen and nitrogen. The bromide ions in (η<sup>2</sup>-TEMPO)<sub>2</sub>ThBr<sub>2</sub> can be replaced by an additional 2 equiv
of TEMPO in the presence of 2 equiv of KC<sub>8</sub> to form the
perÂ(TEMPO) complex ThÂ(η<sup>1</sup>-TEMPO)<sub>2</sub>(η<sup>2</sup>-TEMPO)<sub>2</sub>. ThBr<sub>4</sub>(THF)<sub>4</sub> reacts
with TEMPO to form ThBr<sub>4</sub>(THF)<sub>2</sub>(η<sup>1</sup>-TEMPO), which contains an oxygen-bound TEMPO radical. The Th<sup>3+</sup> complex (η<sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>H)<sub>3</sub>Th is oxidized in the presence of TEMPO, without ligand
loss, to afford the Th<sup>4+</sup> species (η<sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>H)<sub>3</sub>ThÂ(η<sup>1</sup>-TEMPO).
The reactions show that TEMPO can react with organothorium complexes
in several ways including coordination, anion substitution, and cyclopentadienyl
replacement
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