Assembly of azido- or cyano-bridged binuclear complexes containing the bulky [Mn(phen)2]2+ building block:: Syntheses, crystal structures, and magnetic properties

Two new cyano-bridged heterobinuclear complexes, [Mn-II(phen)(2)Cl][Fe-III(bpb)(CN)(2)]center dot 0.5CH(3)CH(2)OH center dot 1.5H(2)O (1) and [Mn-II(phen)(2)Cl][Cr-III(bpb)(CN)2]center dot 2H(2)O (2) [phen = 1,10-phenanthroline; bpb(2-) = 1,2-bis(pyridine-2-carboxamido)-benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn-2(phen)(4)(mu(1,1)-N-3)(2)][M-III (bpb) (CN)(2)](2)center dot H2O [M = Fe (3), Cr (4), Co (5)] and [Mn-2(phen)(4)(mu(1,3)-N-3)(N-3)(2)]BPh(4)center dot 0.5H(2)O (6), have been synthesized and characterized by single-crystal X-ray diffraction analysis and magnetic studies. Complexes 1 and 2 comprise [Mn(phen)(2)Cl](+) 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 aziclo-bridged Mn(II) dimers has been investigated.