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, [MnII(phen)2Cl][FeIII(bpb)(CN)2]·0.5CH3CH2OH·1.5H2O (1) and [MnII(phen)2Cl][CrIII(bpb)(CN)2]·2H2O (2) [phen = 1,10-phenanthroline; bpb2- = 1,2-bis(pyridine-2-carboxamido)benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn2(phen)4((mu)1,1-N3)2][MIII(bpb)(CN)2]2·H2O [M = Fe (3), Cr (4), Co (5)] and [Mn2(phen)4((mu)1,3-N3)(N3)2]BPh4·0.5H2O (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 JMnFe = -2.68(3) cm^-1 and JMnCr = -4.55(1) cm^-1 on the basis of the Hamiltonian H= -JSMnSM(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 = -JSMn1SMn2), respectively. The single EE azido-bridged dimeric complex 6 manifests antiferromagnetic interaction with J = -2.29(4) cm^-1 (H = -JSMn1SMn2). Magneto-structural correlationship on the EO azido-bridged Mn(II) dimers has been investigated.