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Anion exchange of BF4− occurs by stirring a cobalt(III) complex of salen-type ligand tethered by four quaternary ammonium BF4− salts over a slurry of NaX in CH2Cl2, affording a complex containing four X's per cobalt (X = 2,4,5-trichlorophenolate, 6; X = 4-nitrophenolate, 10; X = 2,4-dichlorophenolate, 12). The 1H and 13C NMR spectra are in agreement with an unusual imine uncoordinated structure. The two salen-phenoxys and the two X's persistently coordinate with cobalt(III) to form a square planar cobaltate complex while the other two X's scramble through coordination and decoordination to the axial sites of the square plane. Another form of the complex (X = 2,4,5-trichlorophenolate, 14; X = 4-nitrophenolate, 15; X = 2,4-dichlorophenolate, 16) is also prepared, in which the scrambling two X's in 6, 10, or 12 are replaced with the corresponding [XHX]− homoconjugate. These complexes, which adopt an unusual imine uncoordinated structure, are excellent catalysts for CO2/propylene oxidecopolymerization (turnover frequency (TOF), 8300–16000 h−1). In all cases, the complex containing the homoconjugate [XHX]− shows higher activity than the corresponding phenol-free complex. Among the prepared complexes, 4-nitrophenol-4-nitrophenolate homoconjugate complex 15 showed the best performance (TOF, 16000 h−1; selectivity, 98%; Mn, 273000), allowing for replacement of the explosive 2,4-dinitrophenolate complex.
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