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Synthesis and Electrochemistry of Tin(IV) Octaethylcorroles, (OEC)Sn(C6H5) and (OEC)SnCl

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journal contribution
posted on 14.08.1998, 00:00 by Karl M. Kadish, Stefan Will, Victor A. Adamian, Burkhard Walther, Christoph Erben, Zhongping Ou, Ning Guo, Emanuel Vogel
Two Sn(IV) corroles were synthesized and electrochemically examined. The investigated compounds are represented as (OEC)Sn(C6H5) and (OEC)SnCl, where OEC = trianion of 2,3,7,8,12,13,17,18-octaethylcorrole. (OEC)Sn(C6H5) represents the first example of a σ-bonded metallocorrole which does not undergo a metal-centered electrode reaction. Both compounds undergo three reversible one-electron oxidations, all of which occur at the conjugated macrocycle. The reduction of (OEC)SnCl involves an overall two electrons, with the product being spectroscopically identified as a Sn(II) corrole after bulk electrolysis of the starting compound. (OEC)Sn(C6H5) is reversibly reduced by a single electron to give a Sn(IV) corrole π-anion radical. The electrochemically measured HOMO−LUMO gap (defined as the absolute potential difference between the first-ring centered reduction and first ring-centered oxidation) is equal to 2.25 V in benzonitrile, a value which closely approximates what is observed for porphyrins containing octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP) macrocycles. An X-ray crystallographic analysis for the molecular structure of (OEC)Sn(C6H5) is also presented:  monoclinic, P21/n, with a = 13.235(4) Å, b = 14.502(4) Å, c = 18.387(5) Å, β = 95.45(2)°, Z = 4, R = 0.0619.