New aluminum 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenoxides): Structural characterization of an unusual ionic aluminum bisphenoxide [Al(THF)4(Cl)2]+[Al(mcmip)2]−·x THF

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.

Graphical abstractThe synthesis and X-ray structure determination of an ionic aluminum bisphenoxide [Al(THF)4(Cl)2]+[Al(mcmip)2]−.1.1 THF and its neutral analogue (mcmip)Al(CH2CH3)(THF) are reported (mcmipH2: 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol)). Both aluminum bisphenoxides were tested in the copolymerization of cyclohexene oxide with CO2 and delivered aliphatic polycarbonates in good yields with low amounts of carbonate linkages.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► mcmipH2 = 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol. ► New aluminum bisphenoxides using mcpipH2 as ligand. ► The new aluminium mcmip catalyse the copolymerization of cyclohexene oxide with CO2. ► Formation of aliphatic poly(ether-carbonates).