Premium
Univalent Gallium Complexes of Simple and ansa ‐Arene Ligands: Effects on the Polymerization of Isobutylene
Author(s) -
Lichtenthaler Martin R.,
Maurer Steffen,
Mangan Robert J.,
Stahl Florian,
Mönkemeyer Florian,
Hamann Julian,
Krossing Ingo
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404833
Subject(s) - gallium , isobutylene , chemistry , hexamethylbenzene , crystallography , polymerization , medicinal chemistry , tris , stereochemistry , polymer chemistry , polymer , organic chemistry , biochemistry , copolymer , benzene
Using [Ga(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − ( 1 ) (R F =C(CF 3 ) 3 ) as starting material, we isolated bis‐ and tris‐ η 6 ‐coordinated gallium(I) arene complex salts of p ‐xylene (1,4‐Me 2 C 6 H 4 ), hexamethylbenzene (C 6 Me 6 ), diphenylethane (PhC 2 H 4 Ph), and m ‐terphenyl (1,3‐Ph 2 C 6 H 4 ): [Ga(1,4‐Me 2 C 6 H 4 ) 2.5 ] + ( 2 + ), [Ga(C 6 Me 6 ) 2 ] + ( 3 + ), [Ga(PhC 2 H 4 Ph)] + ( 4 + ) and [(C 6 H 5 F)Ga( μ ‐1,3‐Ph 2 C 6 H 4 ) 2 Ga(C 6 H 5 F)] 2+ ( 5 2+ ). 4 + is the first structurally characterized ansa ‐like bent sandwich chelate of univalent gallium and 5 2+ the first binuclear gallium(I) complex without a GaGa bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI‐BP86/SV(P) level), [Ga(PhC 2 H 4 Ph)] + [Al(OR F ) 4 ] − ( 4 ) and [(C 6 H 5 F)Ga( μ ‐1,3‐Ph 2 C 6 H 4 ) 2 Ga(C 6 H 5 F)] 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‐Me 3 C 6 H 3 ) 2 ] + [Al(OR F ) 4 ] − salt ( 6 ) (1,3,5‐Me 3 C 6 H 3 =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.