20 research outputs found
Facile Reversibility by Design: Tuning Small Molecule Capture and Activation by Single Component Frustrated Lewis Pairs
A series of single component FLPs
has been investigated for small
molecule capture, with the finding that through tuning of both the
thermodynamics of binding/activation and the degree of preorganization
(i.e., Î<i>S</i><sup>⧧</sup>) reversibility
can be brought about at (or close to) room temperature. Thus, the
dimethylxanthene system {(C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>(O)ÂCMe<sub>2</sub>}Â(PMes<sub>2</sub>)Â(BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>): (i) heterolytically cleaves dihydrogen to give an equilibrium
mixture of FLP and H<sub>2</sub> activation product in solution at
room temperature and (ii) reversibly captures nitrous oxide (uptake
at room temperature, 1 atm; release at 323 K)
Interaction of In(I) and Tl(I) Cations with 2,6-Diaryl Pyridine Ligands: Cation Encapsulation within a Very Weakly Interacting N/Arene Host Environment
The interaction of 2,6-dimesitylpyridine with TlÂ(I) and
InÂ(I) cations
has been investigated with a view to developing tractable molecular
MÂ(I) compounds which are soluble in organic media. In stark contrast
to isosteric and isoelectronic terphenyl systems, complexes featuring
the [(2,6-Mes<sub>2</sub>py)ÂM]<sup>+</sup> fragment feature very weak
metalâligand interactions in the solid state, as revealed by
M-N distances of the order of 2.45 Ă
(M = In) and 2.64 Ă
(M = Tl). While additional weak Ï interactions are observed
with arene solvate molecules in these systems, the related 2:1 complex
[(2,6-Mes<sub>2</sub>py)<sub>2</sub>In]Â[BAr<sup><i>f</i></sup><sub>4</sub>] features an InÂ(I) center wholly encapsulated
by the bulky Mes<sub>2</sub>py donors, and even longer InâN
distances [2.586(6) and 2.662(5) Ă
]. These contacts are about
0.5 Ă
greater than the sum of the respective covalent radii (2.13
Ă
) and provide evidence for an effectively ânakedâ
InÂ(I) cation stabilized to a minor extent by orbital interactions
Aminoborane Ï Complexes: Significance of Hydride Co-ligands in Dynamic Processes and Dehydrogenative Borylene Formation
Systems of the type [(<i>p</i>-cym)ÂRuÂ(PR<sub>3</sub>)Â(H)Â(H<sub>2</sub>BN<sup><i>i</i></sup>Pr<sub>2</sub>)]<sup>+</sup> (R = Cy, Ph) can be synthesized
from (<i>p</i>-cym)ÂRuÂ(PR<sub>3</sub>)ÂCl<sub>2</sub> and
H<sub>2</sub>BN<sup><i>i</i></sup>Pr<sub>2</sub>/NaÂ[BAr<sup><i>f</i></sup><sub>4</sub>] and are best formulated as
(hydrido)ruthenium Îș<sup>1</sup>-aminoborane complexes. VT-NMR
measurements have been used to probe
the Ï-bond metathesis process leading to RuâH/HâB
exchange, yielding an activation barrier of Î<i>G</i><sup></sup><sup>⧧</sup> = 7.5 kcal mol<sup>â1</sup> at 161 K. Moreover, in contrast to the case for related non-hydride-containing
systems, reactivity toward alkenes constitutes a viable route to a
metal borylene complex via sacrificial hydrogenation
Aminoborane Ï Complexes: Significance of Hydride Co-ligands in Dynamic Processes and Dehydrogenative Borylene Formation
Systems of the type [(<i>p</i>-cym)ÂRuÂ(PR<sub>3</sub>)Â(H)Â(H<sub>2</sub>BN<sup><i>i</i></sup>Pr<sub>2</sub>)]<sup>+</sup> (R = Cy, Ph) can be synthesized
from (<i>p</i>-cym)ÂRuÂ(PR<sub>3</sub>)ÂCl<sub>2</sub> and
H<sub>2</sub>BN<sup><i>i</i></sup>Pr<sub>2</sub>/NaÂ[BAr<sup><i>f</i></sup><sub>4</sub>] and are best formulated as
(hydrido)ruthenium Îș<sup>1</sup>-aminoborane complexes. VT-NMR
measurements have been used to probe
the Ï-bond metathesis process leading to RuâH/HâB
exchange, yielding an activation barrier of Î<i>G</i><sup></sup><sup>⧧</sup> = 7.5 kcal mol<sup>â1</sup> at 161 K. Moreover, in contrast to the case for related non-hydride-containing
systems, reactivity toward alkenes constitutes a viable route to a
metal borylene complex via sacrificial hydrogenation
Reactivity of Boryl- and Silyl-Substituted Carbenoids toward Alkynes: Insertion and Cycloaddition Chemistry
Three
modes of reactivity of phenyl-substituted alkynes toward
acyclic tetrelenes are reported, with reaction pathways found to be
dependent not only on the nature of the group 14 element but also
on the supporting ligand set. Systems featuring SnâB or GeâB
bonds undergo insertion chemistry, forming borane-appended (vinyl)ÂSn<sup>II</sup> and Ge<sup>II</sup> species. With a bisÂ(amido)Âstannylene,
phenylacetylene acts as a protic acid, generating a Sn<sup>II</sup> acetylide with a unique bridged structure. Reactivity toward a more
strongly reducing Si<sup>II</sup> system is dominated by the possibility
of accessing Si<sup>IV</sup> via [2 + 1] cycloaddition chemistry
Facile Reversibility by Design: Tuning Small Molecule Capture and Activation by Single Component Frustrated Lewis Pairs
A series of single component FLPs
has been investigated for small
molecule capture, with the finding that through tuning of both the
thermodynamics of binding/activation and the degree of preorganization
(i.e., Î<i>S</i><sup>⧧</sup>) reversibility
can be brought about at (or close to) room temperature. Thus, the
dimethylxanthene system {(C<sub>6</sub>H<sub>4</sub>)<sub>2</sub>(O)ÂCMe<sub>2</sub>}Â(PMes<sub>2</sub>)Â(BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>): (i) heterolytically cleaves dihydrogen to give an equilibrium
mixture of FLP and H<sub>2</sub> activation product in solution at
room temperature and (ii) reversibly captures nitrous oxide (uptake
at room temperature, 1 atm; release at 323 K)
Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX<sub>2</sub> Radicals
Monomeric five-valence-electron bisÂ(boryl)
complexes of gallium,
indium, and thallium undergo oxidative MâC bond formation with
2,3-dimethylbutadiene, in a manner consistent with both the redox
properties expected for M<sup>II</sup> species and with metal-centered
radical character. The weaker nature of the MâC bond for the
heavier two elements leads to the observation of reversibility in
MâC bond formation (for indium) and to the isolation of products
resulting from subsequent BâC reductive elimination (for both
indium and thallium)
Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX<sub>2</sub> Radicals
Monomeric five-valence-electron bisÂ(boryl)
complexes of gallium,
indium, and thallium undergo oxidative MâC bond formation with
2,3-dimethylbutadiene, in a manner consistent with both the redox
properties expected for M<sup>II</sup> species and with metal-centered
radical character. The weaker nature of the MâC bond for the
heavier two elements leads to the observation of reversibility in
MâC bond formation (for indium) and to the isolation of products
resulting from subsequent BâC reductive elimination (for both
indium and thallium)
Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX<sub>2</sub> Radicals
Monomeric five-valence-electron bisÂ(boryl)
complexes of gallium,
indium, and thallium undergo oxidative MâC bond formation with
2,3-dimethylbutadiene, in a manner consistent with both the redox
properties expected for M<sup>II</sup> species and with metal-centered
radical character. The weaker nature of the MâC bond for the
heavier two elements leads to the observation of reversibility in
MâC bond formation (for indium) and to the isolation of products
resulting from subsequent BâC reductive elimination (for both
indium and thallium)
Syntheses and Anion Binding Capabilities of Bis(diarylboryl) Ferrocenes and Related Systems
Isomeric diborylated ferrocenes featuring
1,1âČ-, 1,2-, and
1,3-substitution patterns have been targeted via a combination of
electrophilic
aromatic substitution
and directed ortho-lithiation protocols. While none of these systems
are competent for the Lewis acid chelation of fluoride, related systems
featuring a mixed B/Si acceptor set capture 1 equiv of fluoride via
a SiâFâB bridging motif