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The reaction of anhydrous FeBr2 with two equivalents of anionic N-heterocyclic carbene (NaL1 and NaL2), which are generated in situ by the reaction of the corresponding salt [4-R-C6H4COCH2{CH- (NCHCHNiPr)}Br] (R = OCH3, H2L1Br, 1; R = F, H2L2Br, 2) with two equivalents of NaN(SiMe3)2, affords bis-ligand Fe(II) complexes of L12Fe (3) and L22Fe (4) in high yield, respectively. Attempt to synthesize mono-ligand Fe(II) bromide by the 1:1 molar ratio of NaL to FeBr2 is unsuccessful, and the same com- plexes of 3 and 4 were obtained. Both 3 and 4 have been depicted by elemental analysis and X-ray structure determination. Preliminary studies show that both 3 and 4 can be used as single-component catalyst for the ring-opening polymerization of ε-caprolactone, and the catalytic activity of 3 is higher than that of 4.
The reaction of anhydrous FeBr2 with two equivalents of anionic N-heterocyclic carbene (NaL1 and NaL2), which are generated in situ by the reaction of the corresponding salt [4-R-C6H4COCH2 {CH- (NCHCHNiPr)} Br] OCH3, H2L1Br, 1; R = F, H2L2Br, 2) with two equivalents of NaN (SiMe3) 2, affords bis- ligand Fe (II) complexes of L12Fe (3) and L22Fe to synthesize mono-ligand Fe (II) bromide by the 1: 1 molar ratio of NaL to FeBr2 is unsuccessful, and the same com- plexes of 3 and 4. Both 3 and 4 have been described by elemental analysis and X- Preliminary studies show that both 3 and 4 can be used as a single-component catalyst for the ring-opening polymerization of ε-caprolactone, and the catalytic activity of 3 is higher than that of 4.