für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. Monoand Dinuclear fri/?/i0S-Metal(II)-Complexes with Nitriles as Co-Ligands

Dicyanomethanides, [RC(CN)(2)](-) (1(-)), are bridging ligands with an angular clamp-type shape. In the tripod/iron(II) system, [tripod = CH3C(CH2PPh2)(3)], they form binuclear species with three of the clamp-type ligands bridging two iron centers. An appropriate stoichiometric mixture of the tripod ligand, iron(II) salts and the dicyanomethanide ligand leads to the exclusive formation of [tripodFe{mu -NC-C(R)-CN)(3)-Fetripod](+) (3(+)), Altogether, seven constituent groups arrange themselves in this type of aggregate. The process of self-aggregation is distinctly modified by the presence of cyanide ions that may act as linear rod-type bridging ligands. Equimolar mixtures of tripod, iron(II) salts, dicyanomethanide ligands and cyanide form tetranuclear aggregates [(tripodFe)(3){mu -NC-C(R)-CN}(3){mu -CN}(3)FeX](+) (5(+)). In these species, the iron centers form a trigonal-pyramidal arrangement with three octahedrally coordinated low-spin tripodiron(II) entities in the basal plane and a tetrahedrally coordinated high-spin iron(II) at the apex. The iron centers in the basal plane are connected by mu (2)-bridging dicyanomethanide ligands. The apical iron center is coordinated by the N-termini of three cyano ligands, which complete the octahedral coordination of the basal low-spin iron(II) centers. The fourth, external ligand X at the tetrahedrally coordinated high-spin iron(H) apex can be varied, but in most cases it is found to be a terminally coordinated dicyanomethanide entity, Without counting this variable ligand X, thirteen constituent groups of four different types selectively aggregate to form the cage compounds 5(+.) While the dinuclear compounds 3 are diamagnetic, the tetranuclear species 5(+) have magnetic moments close to the spin-only value of mu (S.O.) = 4.9 mu (B), for tetrahedral high-spin iron(II). The Mossbauer spectra are in agreement with the description of 5(+) above, which contain three low-spin tripodiron(II) entities and one high-spin iron(II) center. The synthesis, spectroscopic data, cyclic voltammetric data, Mossbauer data and X-ray analytical data for a series of compounds of types 3(+) and 5(+) are presented in this paper.

The triphos ligand CH3C(CH2PPh2)(3) reacts with Co(BF4)(2) (aq) or Fe(BF4)(2) (aq) in the presence of nitriles RCN to produce the pentacoordinate [triphosCo(NCR)(2)](BF4)(2) (1) or the hexacoordinate [triphosFe(NCR)(3)](BF4)(2) (2). With alpha,omega-dinitriles NC-X-CN dinuclear compounds [triphosFe(NC-X CN)(3)Fetriphos](BF4)(4) (X = (CH2)(3) (3a) X = O-C6H4 (3b) are formed. The compound [triphosFe((CH3)(2)C=C(CN)(2))(3)Fetriphos] (3c) is obtained from FeCl2 by addition of the triphos ligand, the dinitrile and NaPF6. All compounds are characterised by the usual analytical techniques including X-ray analyses. It is observed that the quadruply positively charged compounds 3 tend to associate the respective anions in pockets formed by the three segments of the Fe(NC-X-CN)(3)Fe bridging units.

Abstract The triphos ligand CH3C(CH2PPh2)3 reacts with Co(BF4)2 (aq) or Fe(BF4)2 (aq) in the presence of nitriles RCN to produce the pentacoordinate [triphosCo(NCR)2](BF4)2 (1) or the hexacoordinate [triphosFe(NCR)3](BF4)2 (2). With α,ω-dinitriles NC-X-CN dinuclear compounds [triphosFe(NC-X-CN)3Fetriphos](BF4)4 (X = (CH2)3 (3a) X = o-C6H4 (3b) are formed. The compound [triphosFe((CH3)2C=C(CN)2)3Fetriphos](PF6)4 (3c) is obtained from FeCl2 by addition of the triphos ligand, the dinitrile and NaPF6. All compounds are characterised by the usual analytical techniques including X-ray analy­ses. It is observed that the quadruply positively charged compounds 3 tend to associate the respective anions in pockets formed by the three segments of the Fe(NC-X-CN)3Fe bridg ing units.

The conformational space spanned by tripod metal templates CH3C(CH(2)Ph(2))(3)M is analysed on the basis of the solid-state structures of 82 tripodCo templates in compounds tripodCoL(2) and tripodCoL(3). Systematic analysis, including the techniques of conformational space group scatter graphs, principal component analysis, and partial least squares, reveals a series of basic regularities: The torsion of the phenyl groups is strongly linked to the torsional skew of the bicyclooctane-type framework of the chelate cage. For one sense of this skew there are two classes of low-energy conformation that differ by the helicity of the phenyl arrangement and by the degree of torsional skew in the chelate backbone. From the scatter graphs it is evident that a change in helicity may occur by one- or by two-ring flip mechanisms. The basic regularities found by the above methods are also evident from the analysis of the same data by a neural network approach. The fact that these regularities are found for tripodCoL(2) and tripodCoL(3), irrespective of the widely different coligands L and crystal environments, means that the conformation of the tripod metal templates is governed by the forces acting within them and not so much by the forces imposed on them by their individual chemical or crystal environment. It is shown that the classifications, although derived from a data basis only containing Co compounds, are characteristic for tripod metal templates irrespective of the specific metal involved.

In a one-pot reaction from 15 components, a tetra-hedral host-guest compound forms by self-assembly. Its tripod–iron(II) groups are the corners of a tetrahedron (depicted on the right). The edges of the tetrahedron are bridged by 1,2-dinitrile ligands, and a BF ion is encapsulated in the tetrahedral cavity.

Dinuclear Tripod Cobalt Complexes with Bridging 1,4,5,8‐Tetraoxonaphthalene and 1,4,9,10‐Tetraoxoanthracene Ligands: Structures, Spectroscopic, Magnetic, and Electrochemical PropertiesThe syntheses, structures, optical, magnetic, and redox properties of dinuclear tripodcobalt(II) complexes [tripod = CH3C(CH2PPh2)3] with briding 1,4,5,8‐tetraoxonaphthalene 12‐ and 1,4,9,10‐tetraoxoanthracene 22‐ are described. UV/Vis/NIR spectroscopy indicates interaction between the ligand and the metal orbitals. The magnetic interactions involving the two cobalt(II) centers and the bridging ligand are characterized by EPR spectroscopy and magnetic measurements and are analyzed in terms of qualitative Molecular Orbital calculations. The redox chemistry of these complexes is investigated by cyclic voltammetry and interpreted as metal‐based oxidations and ligand‐based reductions.

In einer Eintopfreaktion bildet sich aus 15 Komponenten durch Selbstorganisation eine tetraedrische Wirt‐Gast‐Verbindung. Die Eckpunkte des Tetraeders (siehe rechts) bilden Tripod‐Eisen(II)‐Gruppen, die Kanten sind durch 1,2‐Dinitril‐Liganden überbrückt, im tetraedrischen Hohlraum ist ein BF4−‐Ion eingebaut.magnified image