Synthesis and Reactivity of (C₆F₅)₃BN‐heterocycle Complexes, 2

Abstract

Summary: The reaction of pyrroles and indoles with perfluoroarylboranes produces 1:1 B‐N complexes that contain highly acidic sp3 methylenes. These complexes are stable and can be used as a proton source for the generation of methylmetallocene cations. Indole is preferred over pyrrole. The 1:1:1 borane:indole:dimethylmetallocene compositions are, in some instances, more active than the 500:1 MAO:metallocene catalysts. In addition, the Ind2ZrMe2/IndoleB(C6F5)3 and related catalyst systems require a lower amount of AlR3 scavenger and are more stable compared to the Ind2ZrMe2/B(C6F5)3 catalyst. Also, Ind2ZrCl2/Al(i‐Bu)3/indoleB(C6F5)3 is an active catalyst system. In ethylene/propylene solution copolymerization catalyzed by Ind2ZrMe2, the most active cocatalysts are indoleB(C6F5)3 and 5‐benzyloxy‐indoleB(C6F5)3.Formation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.imageFormation of the catalyst system [Ind2ZrMe]+[B(indolyl)(C6F5)3]−.

Chemical Behavior of a Pair of (COD)CpRh and −Ir Complexes with Pendant Peripheral −B(C6F5)2Groups

“…The observation of the formation of 15 does point to the possibility that the very minor equilibrium component (11) can be actively involved in catalysis. In view of earlier observations it is likely that in this system the pyrrole f 2H-pyrrole tautomerization is catalyzed 20,21,24 by the reactive trivalent boron Lewis acid in 11, which then subsequently traps the obtained isopyrrole ligand. 27 So it may be envisaged that the pair of isomers in such systems (here 13/11) could serve as specific catalyst or reagents in future chemical transformations.…”

“…In order to stabilize the boron center in the open [Ir/B] isomer 11, isomerization to the "isopyrrole" reagent is required. This has been known to be effected 20,21 by the strong boron Lewis acid B(C 6 F 5 ) 3 . 22,23 Consequently, the reaction of complex 13 with pyrrole took ca.…”

Nonchelated d0 Zirconium−Alkoxide−Alkene Complexes

“…These results imply that Cp* 2 YR(alkene) adducts ( L ) are formed and undergo fast intermolecular exchange with free alkene on the NMR time scale. Resconi characterized an [(indenyl) 2 ZrMe][indole·B(C 6 F 5 ) 3 ] ion pair ( M ), which NMR evidence implies is held together by η 2 -CC indole coordination …”

“…Resconi characterized an [(indenyl) 2 ZrMe]-[indole‚B(C 6 F 5 ) 3 ] ion pair (M), which NMR evidence implies is held together by η 2 -CdC indole coordination. 18 In addition to these d 0 transition metal-alkene complexes, other alkene complexes in which π-back-bonding is absent have been reported, including chelated metal-alkene adducts of alkali metals, 19 alkaline earth metals, 20 Sm III , 21 and Al, Ga, and In, 22 as well as norbornyl-type cations in which an alkene is coordinated to Si, Ge, Sn, or Pb. 23 The ion pair [Bu 3 Sn][H 2 Cd CHCH 2 B(C 6 F 5 ) 3 ], which is generated from B(C 6 F 5 ) 3 and Bu 3 -SnCH 2 CHdCH 2 , may be viewed as an alkene complex of Bu 3 Sn + and exhibits NMR properties that are similar to those of d 0 transition metal-alkene complexes.…”

Structure−Reactivity Relationships of Amido-Pyridine-Supported Rare-Earth-Metal Alkyl Complexes

“…Equimolar mixtures of dimethyl zirconocenes and N -[tris(pentafluorophenyl)borane]-3 H -indole provided significantly higher catalytic activities than systems activated by methylalumoxane (MAO) or B(C 6 F 5 ) 3 /Al i Bu 3 . N -[Tris(pentafluorophenyl)borane]-3 H -indole, derived from the reaction of indole with B(C 6 F 5 ) 3 , contains a highly acidic sp 3 carbon (indicated in Scheme ), generated by a formal N→C hydrogen shift . This soluble proton source provides a convenient method for generating cationic alkyl metallocene precatalysts .…”