A low-spin iron nitrosyl complex from the reaction of NO with (5H, 14H-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetra-azacyclotetradecinato)iron(II), and its crystal structure

Abstract

The reaction of NO with [FeL]·thf, (1)(H₂L = 5H, 14H-6,8,15,17-tetramethyldibenzo[b,i]-[1,4,8,11]tetra-azacyclotetradecine, thf = tetrahydrofuran) in thf led to a deep green cyrstalline solid [FeL(NO)]·thf, (2). The N–O stretching vibration at 1 636 cm^–1(Nujol) is quite low, if compared to the other nitrosyi derivatives of iron chelate complexes. The low-spin state revealed by the magnetic moment [µ_eff.= 1.91 at 292 K] is confirmed by the structural parameters of (2). The square-pyramidal geometry and bond parameters indicate low-spin Fe^III: the displacement of iron(III) from the N₄ donor plane is 0.386(1)Å, while the average Fe–N distance is 1.944(7)Å. The NO group displays a bent bonding mode [Fe–N–O, 144.1(9)° Fe–N, 1.716(11) and N–O, 1.17(2)Å] in agreement with the low stretching frequency. Complex (2) crystallized in the monoclinic space group P2₁/c with a= 11.397(2), b= 13.767(3), c= 16.080(2)Å, β= 105.67(1)°, Z= 4, R= 0.063.