Univalent gallium salts of weakly coordinating anions: Effective initiators/catalysts for the synthesis of highly reactive polyisobutylene

TY - JOUR

T1 - Univalent gallium salts of weakly coordinating anions

T2 - Effective initiators/catalysts for the synthesis of highly reactive polyisobutylene

AU - Lichtenthaler, M.R.

AU - Higelin, A.

AU - Kraft, A.

AU - Hughes, S.

AU - Steffani, A.

AU - Plattner, D.A.

AU - Slattery, J.M.

AU - Krossing, I.

PY - 2013/11/25

Y1 - 2013/11/25

N2 - The scope of the univalent gallium salts [Ga(CH F)][Al(OR)] and the new completely characterized [Ga(1,3,5-MeC H)][Al(OR) ] (R = C(CF)) 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(CHF)][Al(OR )] (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 HF)][Al(OR) ] for the electron richer [Ga(1,3,5-MeC H)][Al(OR) ], 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.

AB - The scope of the univalent gallium salts [Ga(CH F)][Al(OR)] and the new completely characterized [Ga(1,3,5-MeC H)][Al(OR) ] (R = C(CF)) 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(CHF)][Al(OR )] (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 HF)][Al(OR) ] for the electron richer [Ga(1,3,5-MeC H)][Al(OR) ], 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.

UR - http://www.scopus.com/inward/record.url?scp=84888583465&partnerID=8YFLogxK

U2 - 10.1021/om4005516

DO - 10.1021/om4005516

M3 - Article

AN - SCOPUS:84888583465

SN - 0276-7333

VL - 32

SP - 6725

EP - 6735

JO - Organometallics

JF - Organometallics

IS - 22

ER -