1258429-49-0Relevant articles and documents
Anion variation on a cobalt(iii) complex of salen-type ligand tethered by four quaternary ammonium salts for CO2/epoxide copolymerization
Yoo, Jina,Na, Sung Jae,Park, Hyeong Cheol,Cyriac, Anish,Lee, Bun Yeoul
, p. 2622 - 2630 (2010/06/14)
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 CH2Cl 2, 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 [X...H...X] - homoconjugate. These complexes, which adopt an unusual imine uncoordinated structure, are excellent catalysts for CO2/propylene oxide copolymerization (turnover frequency (TOF), 8300-16000 h-1). In all cases, the complex containing the homoconjugate [X...H...X] - 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. The Royal Society of Chemistry 2010.
