Univalent Gallium Complexes of Simple and ansa‐Arene Ligands: Effects on the Polymerization of Isobutylene

Using Ga(C₆H₅F)₂]⁺Al(OR^F)₄]^?( 1 ) (R^F=C(CF₃)₃) as starting material, we isolated bis‐ and tris‐η⁶‐coordinated gallium(I) arene complex salts of p‐xylene (1,4‐Me₂C₆H₄), hexamethylbenzene (C₆Me₆), diphenylethane (PhC₂H₄Ph), and m‐terphenyl (1,3‐Ph₂C₆H₄): Ga(1,4‐Me₂C₆H₄)_2.5]⁺ ( 2⁺ ), Ga(C₆Me₆)₂]⁺ ( 3⁺ ), Ga(PhC₂H₄Ph)]⁺ ( 4⁺ ) and (C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺ ( 5²⁺ ). 4⁺ is the first structurally characterized ansa‐like bent sandwich chelate of univalent gallium and 5²⁺ the first binuclear gallium(I) complex without a Ga?Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI‐BP86/SV(P) level), Ga(PhC₂H₄Ph)]⁺Al(OR^F)₄]^?( 4 ) and (C₆H₅F)Ga(μ‐1,3‐Ph₂C₆H₄)₂Ga(C₆H₅F)]²⁺{Al(OR^F)₄] ^?}₂ ( 5 ), featuring ansa‐arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR‐PIB). In comparison to the recently published 1 and the Ga(1,3,5‐Me₃C₆H₃)₂]⁺Al(OR^F)₄]^? salt ( 6 ) (1,3,5‐Me₃C₆H₃=mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR‐PIB with high contents of terminal olefinic double bonds (α‐contents=84–93 %), low molecular weights (M_n=1000–3000 g mol^?1) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6 , the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.