Koenig, Seymour H.: I. I. Rabi, F. Bloch, E. M. Purcell, and the History of NMR and Relaxometry

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…[267,268] Ther elated H(P(C 2 O 4 ) 3 )a nd H(P(1,2-O 2 C 6 Cl 4 ) 3 )B rønsted acids are also readily prepared simply from PCl 5 and the corresponding alcohol, and are both strong enough Brønsted acids to protonate diethyl ether. [173,183] Typical Applications of the 4 ] À , [271][272][273] [B-(C 6 F 5 ) 4 ] À , [274] and [P(1,2-O 2 C 6 Cl 4 ) 3 ] À [173] )f or the polymerization of arange of olefins including isobutene, n-butyl vinyl ether, a-methylstyrene,s tyrene,a nd isoprene.I na ddition, [H(OEt 2 ) 2 ][P(1,2-O 2 C 6 Cl 4 ) 3 ]h as also been shown to catalyze the Friedel-Crafts-type alkylation reaction between trimethylhydroquinone and (all-rac)i sophytol to yield all-rac-atocopherol (synthetic vitamin E). However,the reactivity of H[Al(OR F ) 4 ]iscomplicated by the tendency of the alcohol (HOR F )todissociate from the Lewis acid (Al(OR F ) 3 )i ns olution, with Al(OR F ) 3 forming stable and isolable adducts with even weakly coordinating solvents such as fluorobenzene.T herefore,H [Al(OR F ) 4 ]i sp robably best described as aJ anus-headed alcohol-alane adduct that may protonate weakly basic compounds such as mesitylene or diethyl ether in nonpolar solvents to give the [Al(OR F ) 4 ] À counterion, but coordinates more basic s-donating compounds La st he adduct L!Al(OR F ) 3 of the Lewis acid.…”

“…Ther eaction between the corresponding diols and PCl 5 proceeds with evolution of five equivalents of HCl and the last proton is then transferred to the Et 2 Os olvent to form the desired [H(OEt 2 )][WCA]s alt. [173,183] Typical Applications of the Oxonium Acids:M any oxonium acids function as single-component initiators for carbocationic olefin polymerization, which is then supported by the chosen WCA.Examples include the use of [H(OEt 2 ) 2 ]-[WCA]s alts (where WCA = [Al(OR F ) 4 ] À , [271][272][273] [B-(C 6 F 5 ) 4 ] À , [274] and [P(1,2-O 2 C 6 Cl 4 ) 3 ] À [173] )f or the polymerization of arange of olefins including isobutene, n-butyl vinyl ether, a-methylstyrene,s tyrene,a nd isoprene.I na ddition, [H(OEt 2 ) 2 ][P(1,2-O 2 C 6 Cl 4 ) 3 ]h as also been shown to catalyze the Friedel-Crafts-type alkylation reaction between trimethylhydroquinone and (all-rac)i sophytol to yield all-rac-atocopherol (synthetic vitamin E). [183] Oxonium acids have also featured highly in the literature for the protonolysis of metal/main group element-carbon bonds to yield the corresponding cation supported by the WCA.Amultitude of examples are presented in areview on p-block cations.…”

“…Typical Applications of the Oxonium Acids : Many oxonium acids function as single‐component initiators for carbocationic olefin polymerization, which is then supported by the chosen WCA. Examples include the use of [H(OEt 2 ) 2 ][WCA] salts (where WCA=[Al(OR F ) 4 ] − , [B(C 6 F 5 ) 4 ] − , and [P(1,2‐O 2 C 6 Cl 4 ) 3 ] −[173] ) for the polymerization of a range of olefins including isobutene, n ‐butyl vinyl ether, α‐methylstyrene, styrene, and isoprene. In addition, [H(OEt 2 ) 2 ][P(1,2‐O 2 C 6 Cl 4 ) 3 ] has also been shown to catalyze the Friedel–Crafts‐type alkylation reaction between trimethylhydroquinone and (all‐ rac ) isophytol to yield all‐ rac ‐α‐tocopherol (synthetic vitamin E) …”

Grundlegende Bemerkungen zur Azidität

“…Die kationische Polymerisation von Isobuten wird jedes Jahr im 100‐Kilotonnen‐Maßstab durchgeführt und zumeist durch Lewis‐Säuren in Verbindung mit Wasser oder Alkoholen gestartet, die katalytische Mengen an hochaziden Protonen freisetzen. In einer intensiven Zusammenarbeit mit der BASF konnten wir das protonierte Diethylethersalz [H(OEt 2 ) 2 ] + [Al(OR F ) 4 ] − (R F =C(CF 3 ) 3 ) als extrem aktiven Initiator für die Isobutenpolymerisation ausfindig machen . Selbst bei −60 °C und winzigen Konzentrationen bis hinab zu 10 −6 mol L −1 gelöst in 50 mL Dichlormethan sind 20 mL Isobuten (H 2 C=C(CH 3 ) 2 ) in Sekundenschnelle durchpolymerisiert, verbunden mit einem Temperaturanstieg auf 60–70 °C.…”

“…Rechnungen auf Basis experimenteller Daten zufolge ist die Protonierung von Isobuten durch den protonierten Ether [Gl. ], zumindest in der Gasphase, stark exergonisch …”