Selective Cotrimerization of Ethene and Styrenic Comonomers

Chromium catalysts supported by bis(diarylphosphino)amine ligands, on activation with methylaluminoxane (MAO), selectively cotrimerize ethene and styrenic comonomers to give predominantly linear products via 2,1-insertion of comonomer

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers

Frustrated Lewis Pairs beyond the Main Group: Cationic Zirconocene–Phosphinoaryloxide Complexes and Their Application in Catalytic Dehydrogenation of Amine Boranes

The cationic zirconocene–phosphinoaryloxide complexes [Cp2ZrOC6H4P(t-Bu)2][B(C6F5)4] (3) and [Cp*2ZrOC6H4P(t-Bu)2][B(C6F5)4] (4) were synthesized by the reaction of Cp2ZrMe2 or Cp*2ZrMe2 with 2-(diphenylphosphino)phenol followed by protonation with [2,6-di-tert-butylpyridinium][B(C6F5)4]. Compound 3 exhibits a Zr–P bond, whereas the bulkier Cp* derivative 4 was isolated as a chlorobenzene adduct without this Zr–P interaction. These compounds can be described as transition-metal-containing versions of linked frustrated Lewis pairs (FLPs), and treatment of 4 with H2 under mild conditions cleaved H2 in a fashion analogous to that for main-group FLPs. Their reactivity in amine borane dehydrogenation also mimics that of main-group FLPs, and they dehydrogenate a range of amine borane adducts. However, in contrast to main-group FLPs, 3 and 4 achieve this transformation in a catalytic rather than stoichiometric sense, with rates superior to those for previous high-valent catalysts

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers

Frustrated Lewis Pairs beyond the Main Group: Cationic Zirconocene–Phosphinoaryloxide Complexes and Their Application in Catalytic Dehydrogenation of Amine Boranes

The cationic zirconocene–phosphinoaryloxide complexes [Cp2ZrOC6H4P(t-Bu)2][B(C6F5)4] (3) and [Cp*2ZrOC6H4P(t-Bu)2][B(C6F5)4] (4) were synthesized by the reaction of Cp2ZrMe2 or Cp*2ZrMe2 with 2-(diphenylphosphino)phenol followed by protonation with [2,6-di-tert-butylpyridinium][B(C6F5)4]. Compound 3 exhibits a Zr–P bond, whereas the bulkier Cp* derivative 4 was isolated as a chlorobenzene adduct without this Zr–P interaction. These compounds can be described as transition-metal-containing versions of linked frustrated Lewis pairs (FLPs), and treatment of 4 with H2 under mild conditions cleaved H2 in a fashion analogous to that for main-group FLPs. Their reactivity in amine borane dehydrogenation also mimics that of main-group FLPs, and they dehydrogenate a range of amine borane adducts. However, in contrast to main-group FLPs, 3 and 4 achieve this transformation in a catalytic rather than stoichiometric sense, with rates superior to those for previous high-valent catalysts

Avoiding MAO: Alternative Activation Methods in Selective Ethylene Oligomerization

An ionic chromium­(III) species, [CrCl2(THF)4]­[Al­(OC4F9)4] (2), has been synthesized and is shown to react with a variety of bidentate diphosphine ligands to yield complexes of the type [CrCl2(diphosphine)2]­[Al­(OC4F9)4]. When compound 2 is combined with diphosphines Ar2PN­(Me)­PAr2 (Ar = 2-MeO-C6H4) and Ph2PN­(i-Pr)­PPh2, after activation with small amounts of AlMe3, active species for the selective oligomerization of ethylene with catalyst productivities of up to 25010 g gCr–1 h–1 are observed. Selectivity to 1-hexene or 1-octene is a function of ligand structure in an identical fashion to the MAO-activated system. A novel Cr­(II) species, [Cr­(Ar2PN­(Me)­PAr2)2]­[Al­(OC4F9)4]2 (5), was isolated from the catalytic mixture. Compound 5 alone does not oligomerize ethylene, but reaction with MAO yields a highly active catalyst for selective ethylene oligomerization

Frustrated Lewis Pairs beyond the Main Group: Synthesis, Reactivity, and Small Molecule Activation with Cationic Zirconocene–Phosphinoaryloxide Complexes

The extension of the frustrated Lewis pair (FLP) concept to the transition series with cationic zirconocene–phosphinoaryloxide complexes is demonstrated. Such complexes mimic the reactivity of main group FLPs in reactions such as heterolytic hydrogen cleavage, CO2 activation, olefin and alkyne addition, and ring-opening of tetrahydrofuran. The interplay between sterics and electronics is shown to have an important role in determining the reactivity of these compounds with hydrogen in particular. The Zr–H species generated from the heterolytic activation of hydrogen is shown to undergo insertion reactions with both CO2 and CO. Crucially, these transition metal FLPs are markedly more reactive than main group systems in many cases, and in addition to the usual array of reactions they demonstrate unprecedented reactivity in the activation of small molecules. This includes SN2 and E2 reactions with alkyl chlorides and fluorides, enolate formation from acetone, and the cleavage of C–O bonds to facilitate SN2 type reactions with noncyclic dialkyl ethers