Dinuclear metal carboxylates

The simplest complexes exhibiting columnar mesophases are the dinuclear metal carboxylates [M2(02CR)4], derived from simple alkanoic acids which have been synthesized with a range of metals [156]. Early work concentrated upon copper(II) carboxylates, with X-ray studies confirming the phases as hexagonal columnar... 

The dinuclear metal carboxylates M2(02CR)4 represent an important class of transition-metal complexes with respect to the study of structure and metal-metal interactions. Several new chain compounds of dinuclear metal carboxylates have been isolated and some of them show interesting gas-adsorption properties, giving a new aspect of chain complexes. Takamizawa and coworkers [149] presented evidence for a thermodynamic correlation between the phase transition and gas adsorption for a copper complex which was constructed by van der Waals interactions among chain-building blocks. 

Copper Carboxylate Complexes. The structural literature on copper(n) carboxylate complexes prior to 1971 is extorsive a recent report on anti-ferromagnetism in dinuclear copper carboxylates makes reference to nearly forty relevant crystallographic papers a 1967 review of metal-peptide... 

Dinuclear rhodium(II) carboxylate complexes with cage-like structures 46, in which carboxylate groups bridge the two metals and a... 

Further reaction of 53 with diphenyl phosphate afforded a phospho-diester-bridged dinuclear magnesium(II) complex 54. The Mg-Mg distance of 4.11 A is comparable to similar distances in the Klenow fragment of E. coli DNA polymerase I (3.9 A) (39), rat DNA polymerase j8 (4 A) (46), and inositol monophosphatase (3.8 A) (35). The flexibility of the bridging carboxylates in 52 is manifested by the ca. 0.75-A range of Mg-Mg distances in these complexes, which can readily adjust the metal coordination environment. 

The dinuclear catalyst 21-Ba2, in which the azacrown ether units are linked to vicinal positions of the calix 4 arcnc scaffold, is not only superior to its diagonal regioisomer 22-Ba2 in all cases, but is also superior to 17-Ba2 in the reactions of esters 14, 23, and 24. Modest levels of cooperation between metal ions are seen in the catalyzed reactions of the longest substrate 25, which indicates that dinuclear complexes cannot expand their intermetal distances to adapt to the long carboxylate-carbonyl distance in 25. 

Many carboxylic acids exist in the free state as hydrogen-bonded dimers with an oxygen-oxygen separation (between oxygens linked to the same carbon atom) close to 220 pm. Replacement of these hydrogens by two metal atoms results in the close approach of the two metal atoms.28 Much of the interest in these dinuclear paddlewheel systems has been generated by a need to understand the nature of these metal-metal interactions. The natural desire of chemists is to use formal bond orders as an index of this interaction and much has been published to this end. However, there are growing indications that such a formal concept is not entirely appropriate for such systems.29... 

In the 3, 5 -exonuclease reaction of DNA polymerase I, two of the metal ions (Mg, Zn, or Mn) are required for activity, and two slightly different metal sites are available in the enzyme, most likely in a dinuclear center [6] with phosphate and carboxylate ligands for one metal (Mg) and with carboxylates(3), phosphate, and a water ligand for the other metal (Zn) in the transition state [7]. 

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