5 research outputs found
Novel Lanthanide Amides Incorporating Neutral Pyrrole Ligand in a Constrained Geometry Architecture: Synthesis, Characterization, Reaction, and Catalytic Activity
The
first series of lanthanide amido complexes incorporating a
neutral pyrrole ligand in a constrained geometry architecture were
synthesized, and their bonding, reactions, and catalytic activities
were studied. Treatment of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>LnÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> with 1 equiv of (<i>N</i>-C<sub>6</sub>H<sub>5</sub>NHCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N) (<b>1</b>) afforded the
first example of bisamido lanthanide complexes having the neutral
pyrrole η<sup>5</sup>-bonded to the metal formulated as [η<sup>5</sup>:η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]ÂLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> (Ln
= La (<b>2</b>) and Nd (<b>3</b>)). Reaction of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>SmÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> with 2 equiv of <b>1</b> produced the complex [η<sup>5</sup>:η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]Â[η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]]ÂSmNÂ(SiMe<sub>3</sub>)<sub>2</sub> (<b>4</b>). Treatment of <b>3</b> with 2 equiv of <b>1</b> gave the sandwich neodymium complex [η<sup>5</sup>:η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]<sub>2</sub>NdÂ[η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)] (<b>5</b>), in which two neutral pyrroles
bonded with metal in an η<sup>5</sup> mode. Complex <b>5</b> could also be prepared by reaction of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>NdÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> with 3 equiv of <b>1</b>. Reactivities of the lanthanide bisamido complexes were
further investigated. Reaction of complex <b>2</b> with pyrrolyl-functionalized
imine [2-(2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>Nî—»CH)ÂC<sub>4</sub>H<sub>3</sub>NH] afforded a
mixed η<sup>5</sup>-bonded neutral pyrrole and η<sup>1</sup>-bonded anionic pyrrolyl lanthanum complex [η<sup>5</sup>:η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]Â{η<sup>1</sup>-2-[(2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)ÂNCH]ÂC<sub>4</sub>H<sub>3</sub>N}ÂLaÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>] (<b>6</b>). Reactions of complexes <b>2</b> and <b>3</b> with pyrrolyl-functionalized secondary
amine afforded the mixed η<sup>5</sup>-bonded neutral pyrrole
and the η<sup>1</sup>-bonded anionic pyrrolyl lanthanide complexes
[η<sup>5</sup>:η<sup>1</sup>-(<i>N</i>-C<sub>6</sub>H<sub>5</sub>NCH<sub>2</sub>CH<sub>2</sub>)Â(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)]Â[(η<sup>1</sup>-2-<sup><i>t</i></sup>BuNCH)ÂC<sub>4</sub>H<sub>3</sub>N]<sub>2</sub>Ln
(Ln = La (<b>7</b>), Nd (<b>8</b>)) with dehydrogenation
of the secondary amine. Investigation of the catalytic properties
of complexes <b>2</b>–<b>8</b> indicated that all
complexes exhibited a high activity with a high chemo- and regioselectivity
on the addition of dialkyl phosphite to α,β-unsaturated
carbonyl derivatives. An interesting result was found that 1,2-hydrophosphonylation
substrates could be catalytically converted to 1,4-hydrophosphinylation
products when the substrates are the substituted benzylideneacetones
by controlling the reaction conditions
Lanthanide Amido Complexes Incorporating Amino-Coordinate-Lithium Bridged Bis(indolyl) Ligands: Synthesis, Characterization, and Catalysis for Hydrophosphonylation of Aldehydes and Aldimines
Two series of new lanthanide amido complexes supported
by bisÂ(indolyl)
ligands with amino-coordinate-lithium as a bridge were synthesized
and characterized. The interactions of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>Ln<sup>III</sup>(μ-Cl)ÂLiÂ(THF)<sub>3</sub> with
2 equiv of 3-(CyNHCH<sub>2</sub>)ÂC<sub>8</sub>H<sub>5</sub>NH in toluene
produced the amino-coordinate-lithium bridged bisÂ(indolyl) lanthanide
amides [μ-{[η<sup>1</sup>:η<sup>1</sup>:η<sup>1</sup>:η<sup>1</sup>-3-(CyNHCH<sub>2</sub>)ÂInd]<sub>2</sub>Li}ÂLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>] (Cy = cyclohexyl,
Ind = Indolyl, Ln = Sm (<b>1</b>), Eu (<b>2</b>), Dy (<b>3</b>), Yb (<b>4</b>)) in good yields. Treatment of [μ-{[η<sup>1</sup>:η<sup>1</sup>:η<sup>1</sup>:η<sup>1</sup>-3-(CyNHCH<sub>2</sub>)ÂInd]<sub>2</sub>Li}ÂLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>] with THF gave new lanthanide amido complexes
[μ-{[η<sup>1</sup>:η<sup>1</sup>-3-(CyNHCH<sub>2</sub>)ÂInd]<sub>2</sub>LiÂ(THF)}ÂLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>] (Ln = Eu (<b>5</b>), Dy (<b>6</b>), Yb (<b>7</b>)), which can be transferred to amido complexes <b>2</b>, <b>3</b>, and <b>4</b> by reflux the corresponding
complexes in toluene. Thus, two series of rare-earth-metal amides
could be reciprocally transformed easily by merely changing the solvent
in the reactions. All new complexes <b>1</b>–<b>7</b> are fully characterized including X-ray structural determination.
The catalytic activities of these new lanthanide amido complexes for
hydrophosphonylation of both aromatic and aliphatic aldehydes and
various substituted aldimines were explored. The results indicated
that these complexes displayed a high catalytic activity for the C–P
bond formation with employment of low catalyst loadings (0.1 mol %
for aldehydes and 1 mol % for aldimines) under mild conditions.
Thus, it provides a convenient way to prepare both α-hydroxy
and α-amino phosphonates
Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones
A series of lanthanide amido complexes
incorporating a neutral
pyrrole ligand were synthesized and characterized, and their catalytic
activities were studied. Treatment of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>ÂLnÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> with
1 equiv of [(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)ÂCH<sub>2</sub>CH<sub>2</sub>] <sub>2</sub>NH (<b>1</b>) in toluene
afforded the corresponding lanthanide amides with the formula [η<sup>5</sup>:η<sup>1</sup>-(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)ÂCH<sub>2</sub>CH<sub>2</sub>]<sub>2</sub>ÂNLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> (Ln = La (<b>2</b>), Nd (<b>3</b>)). Reaction of <b>2</b> or <b>3</b> with <i>N</i>,<i>N</i>′-dicycloÂhexylÂcarboÂdiimide
(CyNî—»Cî—»NCy) gave the carbodiimide selectively inserted
into the appended Ln–N bond products formulated as CyNCÂ{[<i>N</i>,<i>N</i>-(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)ÂCH<sub>2</sub>CH<sub>2</sub>]<sub>2</sub>N}ÂNCyLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> (Ln = La (<b>4</b>), Nd (<b>5</b>)). Reactions of the lanthanide amides with Me<sub>3</sub>SiCN were also examined. A mixed reaction of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>ÂLaÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub>, [(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>N)ÂCH<sub>2</sub>CH<sub>2</sub>]<sub>2</sub>NH (<b>1</b>), and Me<sub>3</sub>SiCN in toluene at room temperature produced the novel cyano bridged
dinuclear lanthanum complex η<sup>5</sup>:η<sup>1</sup>:η<sup>3</sup>-[(2,5- Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>NÂCH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>N]ÂLaÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]Â(μ-CN)ÂLaÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> (<b>6</b>). The stoichiometric
reactions of lanthanide amides <b>2</b> or <b>3</b> with
Me<sub>3</sub>SiCN produced the novel trinuclear lanthanum and neodymium
complexes {(η<sup>5</sup>:η<sup>1</sup>-[(2,5-Me<sub>2</sub>C<sub>4</sub>H<sub>2</sub>ÂNCH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>N]ÂLnÂ[NÂ(SiMe<sub>3</sub>)<sub>2</sub>]Â(μ-CN)}<sub>3</sub> (Ln = La (<b>7</b>), Nd (<b>8</b>)) through selective
σ-bond metathesis reaction of the terminal Ln–N (NÂ(SiMe<sub>3</sub>)<sub>2</sub>) bond with the Si–C bond of Me<sub>3</sub>SiCN. On the basis of the stoichiometric reactions of complexes <b>2</b>, or <b>3</b> with Me<sub>3</sub>SiCN, complexes <b>2</b>, <b>3</b>, <b>4</b>, <b>5</b>, <b>7</b>, and <b>8</b> as catalysts for cyanosilylation of ketones
were investigated. Results indicated that these complexes displayed
a high catalytic activity on addition of Me<sub>3</sub>SiCN to ketones,
and the activity of the complexes has the order of <b>7</b> ∼ <b>8</b> > <b>2</b> ∼ <b>3</b> ∼ <b>4 ∼ <b>5</b></b>. Thus, complex <b>7</b> or <b>8</b> was proposed
as the active catalyst in the catalytic reaction for the precatalysts
of <b>2</b> and <b>3</b>
Synthesis and Characterization of Organolanthanide Complexes with a Calix[4]-pyrrolyl Ligand and Their Catalytic Activities toward Hydrophosphonylation of Aldehydes and Unactivated Ketones
The alkali metal salt free dinuclear trivalent lanthanide
amido
complexes (η<sup>5</sup>:η<sup>1</sup>:η<sup>5</sup>:η<sup>1</sup>-Et<sub>8</sub>-calixÂ[4]-pyrrolyl)Â{LnNÂ(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub> (Ln = Nd (<b>2</b>), Sm (<b>3</b>), Gd (<b>4</b>)) were prepared through the silylamine
elimination reactions of calix[4]-pyrrole [Et<sub>2</sub>CÂ(C<sub>4</sub>H<sub>2</sub>NH)]<sub>4</sub> (<b>1</b>) with 2 equiv of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>LnÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> (Ln = Nd, Sm, Gd) in toluene at 110 °C. The complexes were
fully characterized by elemental, spectroscopic, and single-crystal
X-ray analyses. Studies on the catalytic activity of the new lanthanide
amido complexes revealed that these complexes can be used as efficient
catalysts for hydrophosphonylation of aldehydes and unactivated ketones,
affording the products in high yields by employing a low catalyst
loading (0.1 mol %) at room temperature in a short time (20 min).
Noteworthy is that it is the first application of calix[4]-pyrrolyl-supported
lanthanide amides as catalysts to catalyze the hydrophosphonylation
of aldehydes and unactivated ketones under mild conditions
Synthesis and Characterization of Organolanthanide Complexes with a Calix[4]-pyrrolyl Ligand and Their Catalytic Activities toward Hydrophosphonylation of Aldehydes and Unactivated Ketones
The alkali metal salt free dinuclear trivalent lanthanide
amido
complexes (η<sup>5</sup>:η<sup>1</sup>:η<sup>5</sup>:η<sup>1</sup>-Et<sub>8</sub>-calixÂ[4]-pyrrolyl)Â{LnNÂ(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub> (Ln = Nd (<b>2</b>), Sm (<b>3</b>), Gd (<b>4</b>)) were prepared through the silylamine
elimination reactions of calix[4]-pyrrole [Et<sub>2</sub>CÂ(C<sub>4</sub>H<sub>2</sub>NH)]<sub>4</sub> (<b>1</b>) with 2 equiv of [(Me<sub>3</sub>Si)<sub>2</sub>N]<sub>3</sub>LnÂ(μ-Cl)ÂLiÂ(THF)<sub>3</sub> (Ln = Nd, Sm, Gd) in toluene at 110 °C. The complexes were
fully characterized by elemental, spectroscopic, and single-crystal
X-ray analyses. Studies on the catalytic activity of the new lanthanide
amido complexes revealed that these complexes can be used as efficient
catalysts for hydrophosphonylation of aldehydes and unactivated ketones,
affording the products in high yields by employing a low catalyst
loading (0.1 mol %) at room temperature in a short time (20 min).
Noteworthy is that it is the first application of calix[4]-pyrrolyl-supported
lanthanide amides as catalysts to catalyze the hydrophosphonylation
of aldehydes and unactivated ketones under mild conditions