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The coupling reaction of epoxides and CO2 is in the focus of many research activities in academia as well as in the industry. In this contribution we report on a versatile aluminum-based homogeneous catalyst utilizing an easy-to-synthesize N2O2 ligand system in combination with various cocatalysts, all of them producing pure alternating poly(cyclohexene carbonate)s with Mn values in the range 10000-15000 g mol-1. This system also efficiently catalyzes the formation of propylene carbonate. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and X-ray structure determination of an uncommon ionic aluminum bisphenoxide [Al(THF)4(Cl)2]+[Al(mcmip)2]−·1.1 THF (1) and its neutral analogue (mcmip)Al(CH2CH3)(THF) (2) are reported (mcmipH2: 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol). The ligand was reacted in THF with diethyl aluminum chloride, respectively triethyl aluminum, under liberation of ethane to yield crystalline aluminum bisphenoxides. Compound 2 exhibits the usual structural features found in neutral THF-aluminum bisphenoxides adducts whereas the ionic compound 1 consists of a cationic octahedral aluminum dichloride moiety, [Al(THF)4(Cl)2], and an anionic di-bisphenoxide aluminate fragment [Al(mcmip)2] containing two 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol) ligands. Both aluminum bisphenoxides were tested as catalysts in the copolymerization of cyclohexene oxide with CO2 and displayed similar good catalytic activities although the carbonate amounts present in the copolymer remain low. [Copyright &y& Elsevier]

Abstract: The synthesis, spectroscopic characterisation and X-ray structure determination of the first aluminium para-chloro-bisphenoxides [Al2(mbpcp)2(C2H5)2(THF)2] and [Al3(mbpcp)2(C2H5)5] (mbpcp=2,2′-methylenebis(4-chlorophenol) are reported. 2,2′-Methylenebis(4-chlorophenol) was reacted with triethyl aluminium to yield under liberation of ethane, aluminium para-chloro-2,2′-methylene-bisphenoxides with different molecular complexities: a dinuclear and a trinuclear specie, both displaying two bridging bisphenoxide ligands. The nature of the solvent (coordinating or not) influences the aggregation degree of the final product. The use of a coordinating solvent like THF yields a dimeric structure with a bisphenol:metal ratio of 1 to 1 which displays a trigonal-bipyramidal coordination geometry around the aluminium atoms whereas using an apolar, weak-coordinating solvent like diethyl ether yields a trinuclear species with a bisphenol:metal ratio of 2 to 3, displaying aluminium atoms with both tetrahedral and trigonal-bipyramidal coordination geometries. These compounds were tested in preliminary screening tests as catalysts of the homopolymerisation of cyclohexene oxide (CHO) and copolymerisation of CHO with carbon dioxide. Both aluminium bisphenoxides are highly active in the ring opening polymerisation of CHO (RT, reaction time <5min, M n ranging from 31000 to 40700g/mol, polydispersities from 1.2 to 1.4). Both compound are also active in the copolymerisation of CHO with CO2 although the carbonate amount remains low (75bar, 90°C, reaction time 8h, M n ranging from 6800 to 15200g/mol, polydispersities from 1.9 to 2.5). [Copyright &y& Elsevier]

Abstract: Reacting triethyl aluminum and diethyl aluminum chloride with the chelating bisphenol ligands mdtbpH2 and mmcpH2 [mmcpH2: 2,2′-methylenebis(4-methyl-6-(1-methyl-cyclohexyl)phenol); mdtbpH2: 2,2′-methylenebis(4,6-di-tert-butyl-phenol)] afforded monomeric and dimeric aluminum bisphenoxides with reactive Al–Cl and Al–C2H5 moieties. We present here the X-ray structure determination of some of the isolated compounds as well as the preliminary catalytic tests in copolymerization reactions with cyclohexene oxide and carbon dioxide. [Copyright &y& Elsevier]