Organometallic paramagnetic

We propose the following classification (i) organometallic paramagnetic compounds (Sections II and III), and (ii) organometallic reactions, in... 

Structural applications range from organic, inorganic and organometallic radicals to coordination complexes and biological macromolecules containing a paramagnetic center. 

The report of the first zinc compound with a Zn-Zn core elicited a number of critical comments on the structure and bonding of decamethyldizincocene, and the interpretation of the results.236,237 None of the authors of these commentaries questioned the data or their interpretation. Parkin, however, has pointed out that the formal oxidation state of +1 for zinc in this compound is merely due to the convention that metals are assigned an oxidation state of 0 when they form bonds with like atoms.237 If the conventional definition of valence, namely the capacity of atoms to form bonds to other atoms is used, then the zinc atoms in decamethyldizincocene are not monovalent, but divalent. The synthesis of a paramagnetic organozinc compound in which zinc uses only one of its two 4s electrons will remain an interesting challenge to many synthetic organometallic chemists. 

Harada A (1994) Stereochemistry of Organometallic and Inorganic Compounds, Vol 5, Chains, Clusters, Inclusion Compounds, Paramagnetic Labels, and Organic Rings. Zanello P (ed), Elsevier, Amsterdam, p 409... 

The temperature dependence of the molar magnetic susceptibility (x) of an assembly of paramagnetic spins without interaction is characterized by the Curie behavior with x = C/T where C = /Vy2( 2.S (.S + l)/3k. It is a very common situation in the organometallic chemistry of radical species when the spin density is essentially localized on the metal atom. Since, in most cases, this atom is surrounded by various innocent ligands, intermolecular interactions are very weak and in most cases are reflected by a small contribution described by a Curie-Weiss behavior, with x = C/(T 0) where 0 is the Curie-Weiss temperature. A positive value for 0 reflects ferromagnetic interactions while a negative value — the most common situation — reflects an antiferromagnetic interaction. 

Whatever the best explanation may be, an indication that allylic alkali metal compounds or allylic carbanions do in fact form the less stable of the two possible acids on neutralization is found in the results of the reduction of aromatic compounds by dissolving metals.376The detection of a paramagnetic intermediate in a similar system and polaro-graphic evidence indicate a one electron transfer in the rate and potential determining step.878 376 The mechanism therefore involves ions (or organometallic intermediates) like the following ... 

Chatgilialoglu, C. In Paramagnetic Organometallic Species in Activation / Selectivity, Catalysis, M. Chanon, M. Julliard, and J. C. Poite (Eds), Kluwer, Dordrecht, 1989, pp. 119-129. (Proceedings of a NATO ARW held in St. Maximin, France, 4-9 October 1987). 

The usual carbon-) 3 chemical shift range of organic compounds ( 250 ppm) considerably expands in organometallic compounds. Paramagnetic metals in metallocenes (Table 4.72) induce particularly large 13C shift values [476]. 

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