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Diazotization of the Amino Acid [closo-1-CB9H8-1-COOH-6-NH3] and Reactivity of the [closo-1-CB9H8-1-COO-6-N2] Anion

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journal contribution
posted on 21.03.2011, 00:00 authored by Bryan Ringstrand, Piotr Kaszynski, Victor G. Young
A comparative study of the reactivity of dinitrogen acids [closo-1-CB9H8-1-COOH-10-N2] (3[10]) and [closo-1-CB9H8-1-COOH-6-N2] (3[6]) was conducted by diazotization of a mixture of amino acids [closo-1-CB9H8-1-COOH-6-NH3] (1[6]) and [closo-1-CB9H8-1-COOH-10-NH3] (1[10]) with NO+BF4 in the presence of a heterocyclic base (pyridine, 4-methoxypyridine, 2-picoline, or quinoline). The 10-amino acid 1[10] formed an isolable stable 10-dinitrogen acid 3[10], while the 6-dinitrogen carboxylate 3[6] reacted in situ, giving products of N-substitution at the B6 position with the heterocyclic solvent (4[6]). The molecular and crystal structures for pyridinium acid 4[6]a were determined by X-ray crystallography. The electronic structures and reactivity of the 6-dinitrogen derivatives of the {1-CB9} cluster were assessed computationally at the B3LYP/6-31G(d,p) and MP2/6-31G(d,p) levels of theory and compared to those of the 10-dinitrogen, 2-dinitrogen, and 1-dinitrogen analogues.