A Highly Lewis Acidic Strontium ansa‐Arene Complex for Lewis Acid Catalysis and Isobutylene Polymerization

Abstract

The potential of a dicationic strontium ansa-arene complex for Lewis acid catalysis has been explored. The key to its synthesis was a simple salt metathesis from SrI 2 and 2 Ag[Al(OR F) 4 ], giving the base-free strontium-perfluoroalkoxyaluminate Sr[Al(OR F) 4 ] 2 (OR F = OC(CF 3) 3). Addition of an ansa-arene yielded the highly Lewis acidic, dicationic strontium ansa-arene complex. In preliminary experiments, the complex was successfully applied as a catalyst in CO 2reduction to CH 4 and a surprisingly controlled isobutylene polymerization reaction.

Unsupported Mg–Alkene Bonding

“…Krossing et al. recently described Ae 2+ (hexamethylbenzene) ions (Ae=Ca, Sr, Ba) stabilized by weakly coordinating aluminate anions [33] and most recently introduced a catalytically active dicationic ansa ‐arene Sr 2+ complex [34] …”

“…recently described Ae 2 + (hexamethylbenzene) ions (Ae = Ca, Sr,B a) stabilized by weakly coordinating aluminate anions [33] and most recently introduced ac atalytically active dicationic ansa-arene Sr 2 + complex. [34] Althought he interaction between Ae metal cationsa nd electron-rich p-arene or p-alkyne ligandsh as been comprehensively investigated, there is currently no information on unsupported Ae metal-alkenec omplexes. Considering their important role as intermediates in catalysis, we now fill this gap by reporting av ariety of Mg complexes with intermolecular bisand mono-alkene ligands, discussm etal-alkene bonding, and provideaDFT study that gives insight into their relative bond energies.…”

Towards Naked Zinc(II) in the Condensed Phase: A Highly Lewis Acidic ZnII Dication Stabilized by Weakly Coordinating Carborate Anions

“…Zn II complexes of electron‐rich arenes Zn(SbF 6 ) 2 ⋅C 6 Me 6 and Zn(SbF 6 ) 2 ⋅C 6 HMe 5 have only been characterized by NMR spectroscopy in SO 2 solution [16] . Only very recently, the structure of Sr[Al{OC(CF 3 ) 3 } 4 ] 2 was reported, which features a partially naked large and therefore less Lewis acidic Sr 2+ cation [17] …”

“…[16] Only very recently, the structure of Sr[Al{OC(CF 3 ) 3 } 4 ] 2 was reported, which features a partially naked large and therefore less Lewis acidic Sr 2+ cation. [17] Zn II salts, considered as borderline Lewis acids in Pearsons HSAB classification, are commonly used as Lewis acids for the mediation of various stoichiometric and catalytic transformations. Well-defined Zn organometallics such as arylzinc species Zn(C 6 F 5 ) 2 are well-established Lewis acid catalysts, especially for the polymerization of various monomers.…”

Partnering a Three‐Coordinate Gallium Cation with a Hydroborate Counter‐Ion for the Catalytic Hydrosilylation of CO2

“…Thus, a variety of homogenous catalytic systems based on metals (Pd/Pt, [14–17] Rh, [18] Re, [19, 20] Ru, [21–26] Ir, [8, 27–30] Co, [13, 31] Mn, [12] Zr, [32, 33] Cu, [34–38] Ni, [39–42] Sc, [43–46] Zn, [47–57] Mg [57, 58] and Sr [59] ), Lewis acids, [60–66] frustrated Lewis pairs (FLPs), [67, 68] organo‐catalysts, [69–75] alkali metal carbonates, [76, 77] and metal borohydrides [78] have been investigated for this process. Many of these catalytic systems feature reactive metal hydride or alkyl groups, which effect the initial activation of CO 2 via insertion.…”