Stefania V. Tomyn

Indefinitely stable iron(IV) cage complexes formed in water by air oxidation

In nature, iron, the fourth most abundant element of the Earths crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation. The complexes can exist indefinitely at ambient conditions without any sign of decomposition in water, nonaqueous solutions and in the solid state. We anticipate that our findings may open a way to aqueous solution and polynuclear high-valent iron chemistry that remains underexplored and presents an important challenge.

Diammine{N-[2-(hy-droxy-imino)-propion-yl]-N'-[2-(oxidoimino)-propion-yl]propane-1,3-diaminido-κ(4) N,N',N'',N'''}iron(III).

In the title compound, [Fe(C9H13N4O4)(NH3)2], the FeIII atom, lying on a mirror plane, is coordinated by four N atoms of a triply deprotonated tetradentate N-[2-(hydroxyimino)propionyl]-N′-[2-(oxidoimino)propionyl]propane-1,3-diaminide ligand in the equatorial plane and two N atoms of two ammonia molecules at the axial positions in a distorted octahedral geometry. A short intramolecular O—H⋯O hydrogen bond between the cis-disposed oxime O atoms stabilizes the pseudo-macrocyclic configuration of the ligand. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into a three-dimensional network. The ligand has a mirror-plane symmetry. One of the methylene groups of the propane bridge is disordered over two sets of sites with equal occupancy factors.

Diammine{N-[2-(hy­droxy­imino)­propion­yl]-N′-[2-(oxidoimino)­propion­yl]propane-1,3-diaminido-κ4N,N′,N′′,N′′′}iron(III)

In the title compound, [Fe(C9H13N4O4)(NH3)2], the FeIII atom, lying on a mirror plane, is coordinated by four N atoms of a triply deprotonated tetradentate N-[2-(hydroxyimino)propionyl]-N′-[2-(oxidoimino)propionyl]propane-1,3-diaminide ligand in the equatorial plane and two N atoms of two ammonia molecules at the axial positions in a distorted octahedral geometry. A short intramolecular O—H⋯O hydrogen bond between the cis-disposed oxime O atoms stabilizes the pseudo-macrocyclic configuration of the ligand. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into a three-dimensional network. The ligand has a mirror-plane symmetry. One of the methylene groups of the propane bridge is disordered over two sets of sites with equal occupancy factors.

Diammine{N-[2-(hydroxyimino)propionyl]-N′-[2-(oxidoimino)propionyl]propane-1,3-diaminido-κ4N,N′,N′′,N′′′}iron(III)

In the title compound, [Fe(C9H13N4O4)(NH3)2], the FeIII atom, lying on a mirror plane, is coordinated by four N atoms of a triply deprotonated tetradentate N-[2-(hydroxyimino)propionyl]-N′-[2-(oxidoimino)propionyl]propane-1,3-diaminide ligand in the equatorial plane and two N atoms of two ammonia molecules at the axial positions in a distorted octahedral geometry. A short intramolecular O—H⋯O hydrogen bond between the cis-disposed oxime O atoms stabilizes the pseudo-macrocyclic configuration of the ligand. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into a three-dimensional network. The ligand has a mirror-plane symmetry. One of the methylene groups of the propane bridge is disordered over two sets of sites with equal occupancy factors.

Diaqua-bis-(pyridine-2-carboxyl-ato-κN,O)manganese(II) dimethyl-formamide hemisolvate.

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

Diaquabis(pyridine-2-carboxylato-κ2N,O)manganese(II) dimethylformamide hemisolvate

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

Diaqua­bis­(pyridine-2-carboxyl­ato-κ2N,O)manganese(II) dimethyl­formamide hemisolvate

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

cis-Bis(2,2'-bipyridine-κN,N')bis-(dimethyl sulfoxide-κO)zinc bis-(tetra-phenyl-borate) dimethyl sulfoxide monosolvate.

In the mononuclear title complex, [Zn(C10H8N2)2(C2H6OS)2](C24H20B)2·C2H6OS, the ZnII ion is coordinated by four N atoms of two bidentate 2,2′-bipyridine molecules and by the O atoms of two cis-disposed dimethyl sulfoxide molecules in a distorted octahedral geometry. The S atom and the methyl groups of one of the coordinated dimethyl sulfoxide molecules are disordered in a 0.509 (2):0.491 (2) ratio. The crystal packing is stabilized by C—H⋯O hydrogen bonds between the dimethyl sulfoxide solvent molecules and tetraphenylborate anions.

Dibromidobis(3,5-dimethyl-1H-pyrazole-κN)cobalt(II).

In the mononuclear title complex, [CoBr2(C5H8N2)2], the CoII atom is coordinated by two N atoms from two monodentate 3,5-dimethylpyrazole ligands and two Br atoms in a highly distorted tetrahedral geometry. In the crystal, the complex molecules are linked by intermolecular N—H⋯Br hydrogen bonds into chains along [101]. An intramolecular N—H⋯Br hydrogen bond is also present.

Aqua­bis(3,5-dimethyl-1H-pyrazole-κN)(oxalato-κ2O,O′)copper(II)

In the title compound, [Cu(C2O4)(C5H8N2)2(H2O)], the CuII atom is coordinated in a slightly distorted square-pyramidal geometry by two N atoms belonging to the two 3,5-dimethyl-1H-pyrazole ligands, two O atoms of the oxalate anion providing an O,O′-chelating coordination mode, and an O atom of the water molecule occupying the apical position. The crystal packing shows a well defined layer structure. Intra-layer connections are realised through a system of hydrogen bonds while the nature of the inter-layer interactions is completely hydrophobic, including no hydrogen-bonding interactions.