The iron centre of the cluster-free hydrogenase (Hmd): low-spin Fe(II) or low-spin Fe(0)?

Infrared data for mono-iron complexes possessing two cis-CO together with Mössbauer data for the enzyme and a model complex support the assignment that the iron centre of the cluster-free hydrogenase Hmd is low-spin Fe(II).

Controlling carbon monoxide binding at di-iron units related to the iron-only hydrogenase sub-site.

Carbon monoxide binding by displacement of a pendant hemi-labile ligand at a di-iron site can be substantially 'switched-on' via a ligand protonation pathway which is competitive with metal-metal bond protonation.

2-[(6-Bromo-2-pyrid-yl)amino]pyridine N-oxide.

In the crystal structure of the title compound, C(10)H(8)BrN(3)O, the dihedral angle between the two pyridine rings is 2.48 (2)°. A weak intramolecular N-H⋯O hydrogen bond is present.

Syntheses, structures, and magnetic properties of cyano-bridged heterobimetallic complexes based on [Fe(bpca)(CN)3]-.

Two new cyano-bridged one-dimensional heterobimetallic coordination polymers, [(bpca)(2)Fe(III)(2)(CN)(6)Cu(H(2)O)(2).1.5H(2)O](n)() (2) and [(bpca)Fe(III)(CN)(3)Cu(bpca)(H(2)O).H(2)O](n)() (3), and a trinuclear complex, [(bpca)(2)Fe(III)(2)(CN)(6)Mn(CH(3)OH)(2)(H(2)O)(2)].2H(2)O (4), have been synthesized using the tailored tricyanometalate precursor (Bu(4)N)[Fe(bpca)(CN)(3)].H(2)O (1) (Bu(4)N(+) = tetrabutylammonium cation; bpca = bis(2-pyridylcarbonyl)amidate anion) as a building block and structurally characterized. In complex 2, the Cu(II) ions are six-coordinated in an elongated distorted octahedral environment, and they are linked by distorted octahedrons of [Fe(bpca)(CN)(3)](-) to form 1D chain of squares. Complex 3 is an unexpected chiral heterobimetallic helical chain complex, in which the helical chain consists of the asymmetric unit of [(bpca)Fe(CN)(3)Cu(bpca)(H(2)O)]. In complex 4, there are two independent trinuclear clusters in one asymmetric unit, and the coordination modes of the two methanol and two water molecules coordinating to the central Mn(II) ion are different (cis and trans). Complex 2 shows metamagnetic behavior with a Neel temperature of T(N) = 2.2 K and a critical field of 250 Oe at 1.8 K, where the cyanides mediate the intrachain ferromagnetic coupling between the Cu(II) and Fe(III) ions. Complex 3 shows ferromagnetic coupling between Cu(II) and Fe(III) ions, the best-fit for chi(M)T versus T using a 1D alternating chain model leads to the parameters J(1) = 7.9(3) cm(-)(1), J(2) = 1.03(2) cm(-)(1), and g = 2.196(3). Complex 4 exhibits ferrimagnetic behavior caused by the noncompensation of the local interacting spins (S(Mn) = 5/2 and S(Fe) = 1/2) which interact antiferromagnetically through bridging cyano groups.

Bis(micro-di-2-pyridylaminato 1-oxide)bis[(trifluoroacetato)copper(II)] acetonitrile disolvate.

The crystal structure of the title compound, [Cu(2)(C(2)F(3)O(2))(2)(C(10)H(8)N(3)O)(2)].2CH(3)CN, contains discrete [Cu(2)(CF(3)COO)(2)(O-dpa)(2)] molecules (O-dpaH is di-2-pyridylamine 1-oxide) which have imposed crystallographic twofold symmetry and an acetonitrile molecule of solvation. The O-dpa(-) ligand is both bidentate and bridging, linking two Cu atoms with a separation of 3.4270 (11) A. Each Cu atom is surrounded by four coordinated atoms that are almost coplanar, with dimensions Cu-N = 1.940 (2) and 1.984 (3) A, and Cu-O = 1.912 (2) and 1.945 (2) A.