Polyoxometalates: Very large clusters - Nanoscale magnets

Main-Group Element, Organic, and Organometallic Derivatives of Polyoxometalates.

The study of paramagnetic compounds based on 4d and 5d transition metals is an emerging research topic in the field of molecular magnetism. An essential driving force for the interest in this area is the fact that heavier metal ions introduce important attributes to the physical properties of paramagnetic compounds. Among the attractive characteristics of heavier elements vis-a-vis magnetism are the diffuse nature of their d orbitals, their strong magnetic anisotropy owing to enhanced spin–orbit coupling, and their diverse structural and redox properties. This critical review is intended to introduce readers to the topic and to report recent progress in this area. It is not fully comprehensive in scope although we strived to include all relevant topics and a large subset of references in the area. Herein we provide a survey of the history and current status of research that has been conducted on the topic of second and third row transition metal molecular magnetism. The article is organized according to the nature of the precursor building blocks with special topics being highlighted as illustrations of the special role of heavier transition metal ions in the field. This paper is addressed to readers who are interested in molecular magnetism and the application of coordination chemistry principles to materials synthesis (231 references).

Molecular magnetic materials based on 4d and 5d transition metals.

Syntheses of sulphur-bridged molybdenum and tungsten coordination compounds

Oxime and oximate metal complexes: unconventional synthesis and reactivity

S 22− as Simultaneous End‐on and Side‐on Bonded Ligand in the Novel Transition‐Metal Complex [Mo4(NO)4S13]4−

MoO42− is reduced by diethyldithiocarbamate (Et2dtc−) on prolonged digestion in aqueous medium whereby the complex [Mo2VO2S2(Et2dtc)2] is formed. The central moiety Mo2O2S22+ has a high formation tendency. When [Mo2V(S2)6]2− is refluxed with Et2dtc− in ethanol, [Mo2VS (Et2dtc)2] is formed, the X-ray crystal structure of which has been determined (space group P212121, a = 10.550(2) A, b = 13.820(5) A, c = 14.723(12) A, dc = 1.90 g · cm3−, Z = 4). The MoMo distance of the diamagnetic compound is 2.817(2) A and the average Mo=St distance 2.099(4) A.



Uber die Darstellung S, S-verbruckter Zweikern-Molybdan(V)-Komplexe. Kristall- und Molekularstruktur von [Mo2S4(Et2dtc)2]



MoO42− wird von Diathyldithiocarbaminat in wasriger Losung reduziert. Die zentrale Einheit MoO2S22+ des gebildeten [Mo2VO2S2(Et2dtc)2] weist eine grose Bildungstendenz auf. [Mo2VS4(Et2dtc)2] last sich aus [Mo2V(S2)6]2− erhalten (Rontgenstrukturkturdaten vgl. Abstract).

On the preparation of binuclear S, S bridged molybdenum(V) complexes crystal and molecular structure of [Mo2S4(Et2dtc)2]

S22− als „end-on" und zugleich „side-on" gebundener Ligand im neuartigen Übergangsmetall-Komplex [Mo4(NO)4S1 3]4−

Die Verbindungen [(C6H5)4P]2[Mo(NO)(H2NO)(NCS)4] 1, [(C6H5)4P]2-[Mo(NO)((C2H5)2CNO)(NCS)4]2, [(C6H5)4P]2[Mo(NO)2(NCS)4] · CH3OH 3, [(C6H5)4P]3[Mo(NO)(CN)5] · 2H2O 4, Cs2[Mo(NO)Cl4(H2O)] 5 und Cs2[Mo(NO)Cl5] 6 wurden dargestellt und durch vollstandige Rontgen-Struktur-Analyse charakterisiert. Alle komplexen Anionen besitzen etwa lineare MoNO-Gruppen, wobei in 1 und 2 eine pentagonalbipyramidale und in 3–6 eine oktaedrische Koordination des Molybdans vorliegt. Komplexe mit {MoNO}n (n = 4, 5, 6)-Konfiguration lassen sich durch bemerkenswerte Redox-Reaktionen ineinander uberfuhren. Einige neuartige Reaktionen des Hydroxyl-amido(−1)-Liganden (Bildung von 2 und 3) werden kurz diskutiert.



Preparation, Redox Properties, and Structures of Mononuclear „Simple” Mono-, and Dinitrosyl Complexes of Molybdenum with Hydroxylamido(−1), Oximato, Halogeno, and Pseudohalogeno Ligands



The compounds [(C6H5)4P]2[Mo(NO)(H2NO)(NCS)4] 1, [(C6H5)4P]2 [Mo(NO)((C2H5)2-CNO)(NCS)4] 2, [(C6H5)4P]2[Mo(NO)2(NCS)4] · CH3OH, 3 [(C6H5)4P]3[Mo(NO)(CN)5] · 2H2O 4, Cs2[Mo(NO)Cl4(H2O)] 5 and Cs2[Mo(NO)Cl5] 6 were prepared and characterized by complete X-ray structure analysis. All complexes have a nearly linear MoNO moiety, whereas in the anions of 1 and 2 a pentagonal-bipyramidal, in 3—6 an octahedral coordination sphere of Mo is present. Complexes with {MoNO}n configuration (n = 4, 5, 6) can be converted into each other by remarkable redox-reactions. Some novel reactions of the hydroxylamido(−1)-ligand (formation of 2 and 3) are discussed very shortly.

Darstellung, Redox‐Verhalten und Strukturen einkerniger „einfacher”︁ Mono‐ und Dinitrosyl‐Komplexe des Molybdäns mit Hydroxylamido(−1)‐, Oximato‐, Halogeno‐ und Pseudohalogeno‐Liganden

N. Mohan

Papers

S 22− as Simultaneous End‐on and Side‐on Bonded Ligand in the Novel Transition‐Metal Complex [Mo4(NO)4S13]4−

On the preparation of binuclear S, S bridged molybdenum(V) complexes crystal and molecular structure of [Mo2S4(Et2dtc)2]

S22− als „end-on" und zugleich „side-on" gebundener Ligand im neuartigen Übergangsmetall-Komplex [Mo4(NO)4S1 3]4−

Darstellung, Redox‐Verhalten und Strukturen einkerniger „einfacher”︁ Mono‐ und Dinitrosyl‐Komplexe des Molybdäns mit Hydroxylamido(−1)‐, Oximato‐, Halogeno‐ und Pseudohalogeno‐Liganden

Approximation methods for the calculation of force constants of a general valence force field in polyatomic molecules - a review