Benzil metal ions

Cz+diimine macrocycle compounds are formed by template condensations of an a-diketone (usually 2,3-butanedione or benzil), 2 + 2 with diamines, e.g., (34), or 1 +1 with tetraamines, e.g., (35) (Scheme 10). The resulting flat macrocycle cations form many stacked compounds, often with flat metal ion-containing anions, which exhibit spin coupling. The imine groups for the Ni11 compounds are reduced with NaBH4 and one of each cz+diimine function for the Co111 compounds by hypophosphorous acid.44... 

In the companion paper (Hanna and Sarac 1977b) the oxidation of benzilic acid is reported with emphasis on learning the mechanistic imphcations with respect to Ce(TV). As is generally observed, the rates are much slower in sulfuric acid solutions and the existence of a stable precursor complex is doubtful. The authors calculate the equihbrium speciation of Ce among the first two hydrolysis products, free metal ion, and 1 1, 1 2, 1 3 Ce-S04 complexes and find that the rate of reaction is most strongly correlated with CeSO ". In the presence of sulfuric acid a precursor complex of the form CeSO HL is proposed. In perchlorate solutions there is some evidence for a reactive CeHL species and an unreactive Ce(HL) " species. The precursor complex stability constant and first-order oxidation rate parameter for the former intermediate are in excellent agreement with those reported by Amjad et al. (1977) for mandelic acid. 

The complexes do not demetallate upon treatment with potassium cyanide, with the exception of square-planar [Pd(L1205)]Cl2, which releases the metal-free LI205 [6]. In the absence of a metal ion, a redox reaction of H(CH3)P(CH2)3P(CH3)H with benzil occurs, resulting in benzoin and 1,2-dimethyl-1,2-diphospholane as the main products [6],... 

Black, D. S. C., Srivastava, R. C. Metal template reactions. I. Benzilic acid rearrangement of dipyridylglyoxal compounds promoted by nickel(ll) and cobalt(ll) ions./tust. J. Chem. 1969, 22, 1439-1447. 

The generality of the rearrangement is further illustrated by the reaction of 2,2 -furil with hydroxide ion in dry ether (Table 1). Likewise, 2,2 -pyridil is rearranged in hot methanol solution (40 min) to give the sodium salt of 2,2 -pyridilic acid (86%). Acidification, however, affords bis(2-pyridyl)methanol by decarboxylation since 2,2 -pyridilic acid (16) is structurally similar to a -keto acid. Benzilic rearrangement of 2,2 -pyridil with methanolic nickel(ll) and cobalt(II) acetates results in the formation of metal complexes of 2,2 -pyridilic acid (17 92%). A plausible mechanism is summarized in Scheme 4. Rearrangement is also observed with 2,2 -quinaldil, but benzil, 2,2 -furil or 1-phenyl-2-(2 -pyridyl)ethane-1,2-dione are not susceptible to these metal template reactions. 

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