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., Δ<i>S</i>^⧧) reversibility can be brought about at (or close to) room temperature. Thus, the dimethylxanthene system {(C₆H₄)₂(O)­CMe₂}­(PMes₂)­(B­(C₆F₅)₂): (i) heterolytically cleaves dihydrogen to give an equilibrium mixture of FLP and H₂ 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 Tl­(I) and In­(I) cations has been investigated with a view to developing tractable molecular M­(I) compounds which are soluble in organic media. In stark contrast to isosteric and isoelectronic terphenyl systems, complexes featuring the [(2,6-Mes₂py)­M]⁺ fragment feature very weak metal–ligand interactions in the solid state, as revealed by M-N distances of the order of 2.45 Å (M = In) and 2.64 Å (M = Tl). While additional weak π interactions are observed with arene solvate molecules in these systems, the related 2:1 complex [(2,6-Mes₂py)₂In]­[BAr^<i>f</i>₄] features an In­(I) center wholly encapsulated by the bulky Mes₂py donors, and even longer In–N distances [2.586(6) and 2.662(5) Å]. These contacts are about 0.5 Å greater than the sum of the respective covalent radii (2.13 Å) and provide evidence for an effectively “naked” In­(I) cation stabilized to a minor extent by orbital interactions

Aminoborane σ Complexes: Significance of Hydride Co-ligands in Dynamic Processes and Dehydrogenative Borylene Formation

Systems of the type [(<i>p</i>-cym)­Ru­(PR₃)­(H)­(H₂BN^<i>i</i>Pr₂)]⁺ (R = Cy, Ph) can be synthesized from (<i>p</i>-cym)­Ru­(PR₃)­Cl₂ and H₂BN^<i>i</i>Pr₂/Na­[BAr^<i>f</i>₄] and are best formulated as (hydrido)ruthenium κ¹-aminoborane complexes. VT-NMR measurements have been used to probe the σ-bond metathesis process leading to Ru–H/H–B exchange, yielding an activation barrier of Δ<i>G</i>^⧧ = 7.5 kcal mol^–1 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 σ Complexes: Significance of Hydride Co-ligands in Dynamic Processes and Dehydrogenative Borylene Formation

Systems of the type [(<i>p</i>-cym)­Ru­(PR₃)­(H)­(H₂BN^<i>i</i>Pr₂)]⁺ (R = Cy, Ph) can be synthesized from (<i>p</i>-cym)­Ru­(PR₃)­Cl₂ and H₂BN^<i>i</i>Pr₂/Na­[BAr^<i>f</i>₄] and are best formulated as (hydrido)ruthenium κ¹-aminoborane complexes. VT-NMR measurements have been used to probe the σ-bond metathesis process leading to Ru–H/H–B exchange, yielding an activation barrier of Δ<i>G</i>^⧧ = 7.5 kcal mol^–1 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 Sn–B or Ge–B bonds undergo insertion chemistry, forming borane-appended (vinyl)­Sn^II and Ge^II species. With a bis­(amido)­stannylene, phenylacetylene acts as a protic acid, generating a Sn^II acetylide with a unique bridged structure. Reactivity toward a more strongly reducing Si^II system is dominated by the possibility of accessing Si^IV 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., Δ<i>S</i>^⧧) reversibility can be brought about at (or close to) room temperature. Thus, the dimethylxanthene system {(C₆H₄)₂(O)­CMe₂}­(PMes₂)­(B­(C₆F₅)₂): (i) heterolytically cleaves dihydrogen to give an equilibrium mixture of FLP and H₂ 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 MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

Syntheses and Anion Binding Capabilities of Bis(diarylboryl) Ferrocenes and Related Systems

Isomeric diborylated ferrocenes featuring 1,1′-, 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 Si–F–B bridging motif