Assembly of Azido- or Cyano-Bridged Binuclear Complexes Containing the Bulky [Mn(phen)₂]²⁺Building Block:  Syntheses, Crystal Structures, and Magnetic Properties

Abstract

Two new cyano-bridged heterobinuclear complexes, [Mn(II)(phen)2Cl][Fe(III)(bpb)(CN)2] x 0.5CH3CH2OH x 1.5H2O (1) and [Mn(II)(phen)2Cl][Cr(III)(bpb)(CN)2] x 2H2O (2) [phen = 1,10-phenanthroline; bpb(2-) = 1,2-bis(pyridine-2-carboxamido)benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn2(phen)4(mu(1,1)-N3)2][M(III)(bpb)(CN)2]2 x H2O [M = Fe (3), Cr (4), Co (5)] and [Mn2(phen)4(mu(1,3)-N3)(N3)2]BPh4 x 0.5H2O (6), have been synthesized and characterized by single-crystal X-ray diffraction analysis and magnetic studies. Complexes 1 and 2 comprise [Mn(phen)2Cl]+ and [M(bpb)(CN)2]- units connected by one cyano ligand of [M(bpb)(CN)2]-. Complexes 3-5 are doubly end-on (EO) azido-bridged Mn(II) binuclear complexes with two [M(bpb)(CN)2]- molecules acting as charge-compensating anions. However, the Mn(II) ions in complex 6 are linked by a single end-to-end (EE) azido bridging ligand with one large free BPh4(-) group as the charge-balancing anion. The magnetic coupling between Mn(II) and Fe(III) or Cr(III) in complexes 1 and 2 was found to be antiferromagnetic with J(MnFe) = -2.68(3) cm(-1) and J(MnCr) = -4.55(1) cm(-1) on the basis of the Hamiltonian H = -JS(Mn)S(M) (M = Fe or Cr). The magnetic interactions between two Mn(II) ions in 3-5 are ferromagnetic in nature with the magnetic coupling constants of 1.15(3), 1.05(2), and 1.27(2) cm(-1) (H = -JS(Mn1)S(Mn2)), respectively. The single EE azido-bridged dimeric complex 6 manifests antiferromagnetic interaction with J = -2.29(4) cm(-1) (H = -JS(Mn1)S(Mn2)). Magneto-structural correlationship on the EO azido-bridged Mn(II) dimers has been investigated.

Crystal Structures and Magnetic Behaviors of Cyanido‐Bridged Dinuclear Dimetallic Systems Involving 3d–3d or 3d–5d Metal Centers

“…The least‐squares fits give magnetic parameters of g = 2.03, J = –6.63 cm –1 , and z J′ = –0.12 cm –1 for 1 ; g = 2.03, J = –7.37 cm –1 , and zJ′ = –0.20 cm –1 for 2 ; g = 1.99, J = –4.46 cm –1 , and zJ′ = –0.08 cm –1 for 3 ; and g = 2.01, J = –8.01 cm –1 , and zJ′ = –0.15 cm –1 for 4 . The J values obtained for 1 – 4 are similar to those for the cyanido‐linked Fe III –Mn II complexes13b,14b,21 and octacyanidotungstate‐based W V –Mn II clusters 22. The negative J values undoubtedly suggest that antiferromagnetic interactions are truly operative through the cyanido bridges.…”

Synthesis, crystal structures, and magnetic properties of two three-dimensional octacyanotungstate(IV)-based bimetallic frameworks with 4,4′-bipyridine dioxide (4,4′-dpdo)

“…In the 3D framework of 2, the nearest Cu…Cu distance is 5.533 Å. [39] . Different from 1, the temperature dependence of the χ m T product in a 1 kOe field for 2 suggests a weak ferromagnetic coupling between the Cu Ⅱ centers bridged by the diamagnetic NC-W-CN groups ( Figure 8).…”

Synthesis and Magnetic Study of μ1,1‐Azido‐Bridged Dinuclear Manganese(II) Complexes Based on Tripyridyl Ligands

“…Recently, Aromí et al found that there is a linear relationship between the exchange coupling constant ( J ) and the Mn–N–Mn bridging angle ( θ ) on the basis of results obtained for only four complexes 15a. We then prepared a series of end‐on azido‐bridged Mn II complexes with the [Mn 2 (phen) 4 (N 3 ) 2 ] 2+ core and improved the J – θ relationship 15b. Apparently, more effort should be exerted to make the assumption of the relation of J and θ more clear.…”