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Self‐Assembly of Tetranuclear Iron(II) Compounds by a Combination of Rod‐ and Clamp‐Shaped Bridging Units
Author(s) -
Jacob Volker,
Mann Susanne,
Huttner Gottfried,
Walter Olaf,
Zsolnai Laszlo,
Kaifer Elisabeth,
Rutsch Peter,
Kircher Peter,
Bill Eckhard
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200109)2001:10<2625::aid-ejic2625>3.0.co;2-t
Subject(s) - bridging (networking) , clamp , crystallography , materials science , chemistry , stereochemistry , computer science , computer graphics (images) , computer network , clamping
Dicyanomethanides, [RC(CN) 2 ] − ( 1 − ), are bridging ligands with an angular clamp‐type shape. In the tripod /iron(II) system, [ tripod = CH 3 C(CH 2 PPh 2 ) 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 [ tripod Fe{μ‐NC−C(R)−CN} 3 Fe tripod ] + ( 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 [{ tripod Fe} 3 {μ‐NC−C(R)−CN} 3 {μ‐CN} 3 FeX] + ( 5 + ). In these species, the iron centers form a trigonal‐pyramidal arrangement with three octahedrally coordinated low ‐ spin tripod iron(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 μ 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(II) 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 μ s.o. = 4.9 μ B , for tetrahedral high ‐ spin iron(II). The Mössbauer spectra are in agreement with the description of 5 + above, which contain three low ‐ spin tripod iron(II) entities and one high ‐ spin iron(II) center. The synthesis, spectroscopic data, cyclic voltammetric data, Mössbauer data and X‐ray analytical data for a series of compounds of types 3 + and 5 + are presented in this paper.