Univalent Gallium Salts of Weakly Coordinating Anions: Effective Initiators/Catalysts for the Synthesis of Highly Reactive Polyisobutylene

Abstract

The scope of the univalent gallium salts [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − and the new completely characterized [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al(OR F ) 4 ] − (R F = C(CF 3 ) 3 ) was investigated in terms of initiating or catalyzing the synthesis of highly reactive poly(2-methylpropylene)highly reactive polyisobutylene (HR-PIB)in several solvents. A series of polymerization reactions proved the high efficiency and quality of the univalent gallium salts for the polymerization of isobutylene. The best results were obtained using very low concentrations of [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − (down to 0.007 mol%) while working at reaction temperatures of up to ±0 °C and in the noncarcinogenic and non-water hazardous solvent toluene. Under these conditions, HR-PIB with an α-content of terminal olefinic double bonds up to 91 mol% and a molecular weight of 1000−2000 was obtained in good yields. Upon changing [Ga(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − for the electron richer [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al-(OR F ) 4 ] − , polymerization temperatures could be increased to +10 °C. The reactivity of the gallium(I) cations therefore seems to be tunable through ligand exchange reactions. Experimental results, density functional theory calculations, and mass spectrometric investigations point toward a coordinative polymerization mechanism. Article pubs.acs.org/Organometallics

Kinetic and Mechanistic Studies of the Polymerization of Isobutylene Catalyzed by EtAlCl2/Bis(2-chloroethyl) Ether Complex in Hexanes

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DSR: enhanced modelling and refinement of disordered structures with SHELXL

“…3 (left) (Lichtenthaler et al, 2013) is located near the positions of atoms O1 and C1 and the maxima in the difference Fourier density map (Q peak positions) of Q4, Q7 and Q6. These three Q peaks correspond to atoms C2, C3 and C4 in the database fragment (Fig.…”