Synthesis and structural characterization of aryloxo-functionalized N-heterocyclic carbene complexes of nickel(II)

Enolate chelating N-heterocyclic carbene complexes of Fe(II): Synthesis, structure and their catalytic activity for ring-opening polymerization of ɛ-caprolactone

“…For example, in 3, the N2-C4-C5-O1 dihedral angle is 8.5°, meanwhile 15.8° and 3.1° in 4. These structural features are very close to these found in a Pd(II) [12] or Ni(II) [13] NHC enolate, and quite different from those presented in a phenolate chelating NHC complex of Fe(II) [11] or Ni(II) [10] . Thus, it is reasonable that the enhanced air and moisture tolerance of 3 and 4 is a consequence of the presence of the coplanar enolate chelating NHC ligand around the iron atom.…”

“…The situation is quite similar to that in the synthesis of Fe(II) complex with phenolate chelating NHC ligand [11] . The results might contribute to either the addition of the second ligand faster than the first one or the disproportionation of mono-ligand Fe(II) halide to a more stable bis-ligand complex [10,11,14] . The proposed structures for 3 and 4 were first supported by elemental analysis.…”

“…Among these complexes, only the complex of Fe(NHC) 2 X 2 has been found to show good catalytic activity for the atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate [3] . Considering the currently increasing attention on iron-based systems [8,9] , further study on the synthesis of iron-based complexes with NHC ligand and their reactivity in homogeneous catalysis is valuable.Very recently, we have designed a novel kind of phenolate chelating NHC ligands [10] and synthesized the first anionic functionalized NHC complex of Fe(II) [11] . It is also found that this kind of iron complex could be used as single-component initiator for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) [11] .…”

“…Very recently, we have designed a novel kind of phenolate chelating NHC ligands [10] and synthesized the first anionic functionalized NHC complex of Fe(II) [11] . It is also found that this kind of iron complex could be used as single-component initiator for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) [11] .…”

Synthesis, structure of functionalized N-heterocyclic carbene complexes of Fe(II) and their catalytic activity for ring-opening polymerization of ε-caprolactone

“…salicylaldiminato-or aryloxo-functionalized NHC ligands, and successfully synthesized the corresponding complexes of Ni(II) with them [16,17]. In order to further extend the application of the anionic functionalized NHC in iron complex, we study the metathesis reaction of FeBr 2 with aryloxo-functionalized NHC sodium salt, [NaO-4,6-di-C(CH 3 ) 3 -C 6 H 2 -2-CH 2 {C(NCH-CHNR)}] (R = CH(CH 3 ) 2 , NaL 1 ; R = CH 2 Ph, NaL 2 ), and successfully synthesized the first bis-aryloxo-functionalized NHC Fe(II) complexes, L 1 2 Fe, 1 and L 2 2 Fe, 2.…”