Work

Mono- to Tetra-nuclear Iron Dichloride Complexes Bearing N -(Fluoro)-aryl-Substituted Iminopyridine Ligands: Synthesis, Structures, Magnetic Properties, and Polymerization of Isoprene

Year: 2025

Type: article

Abstract: The reaction of FeCl 2 with the iminopyridine ligand containing fluorinated N -aryl groups {2-[(Ar)N = C(R)]C 5 H 4 N, where Ar = 3,5-(CF 3 ) 2 C 6 H 3 and R = H ( L1 ) or CH 3 ( L3 ); Ar = C 6 F 5 and R = H ( L2 ) or CH 3 ( L4 ); and iminoquinoline 2-[(3,5-(CF 3 ) 2 (C 6 H 3 )N = CH)]C 9 H 6 N ( L5 )} resulted in distinct iron coordination complexes whose structures were determined by single-crystal X-ray diffraction. Ligands L1 and L2 yielded mononuclear bis-ligated iron dichlorides ( L1 or L2 ) 2 FeCl 2 (complexes 1 and 2 ), while L3 and L5 formed dinuclear complexes ( L3 or L5 ) 2 Fe(μ-Cl 2 )FeCl 2 (complexes 3 and 5 ). Ligand L4 produced an unprecedented tetranuclear dimer [( L4 ) 2 FeCl(μ-Cl 2 )FeCl 2 ] 2 (complex 4 ). Mössbauer spectroscopy revealed single quadrupole doublets for mononuclear complex 2 and two sets of doublets for dinuclear complexes 3 and 5 and tetranuclear complex 4, confirming Fe(II) in high-spin states. Magnetic susceptibility and Curie–Weiss analyses elucidated magnetic interactions, showing reduced effective magnetic moments correlated with increasing Fe-(μ-Cl)-Fe bridges. DFT calculations and NBO analyses supported these findings, highlighting lower charge density on bridging compared to terminal chlorides. Activated by Al i Bu 3 /[CPh 3 ][B(C 6 F 5 ) 4 ], complexes 1 and 2 showed lower activities (TOF = 1,000–1,200 h –1 ) than complexes 3 and 5 (TOF = 90,000 h –1 ) for isoprene polymerization, producing polymers with enriched cis -1,4- alt -3,4 microstructures.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.5c01030