Diazotization of the amino acid [closo-1-CB9H8-1-COOH-6-NH3] and reactivity of the [closo-1-CB9H8-1-COO-6-N2]- anion

A comparative study of the reactivity of dinitrogen acids closo-1-CB(9)H(8)-1-COOH-10-N(2)] (310]) and closo-1-CB(9)H(8)-1-COOH-6-N(2)] (36]) was conducted by diazotization of a mixture of amino acids closo-1-CB(9)H(8)-1-COOH-6-NH(3)] (16]) and closo-1-CB(9)H(8)-1-COOH-10-NH(3)] (110]) with NO(+)BF(4)(-) in the presence of a heterocyclic base (pyridine, 4-methoxypyridine, 2-picoline, or quinoline). The 10-amino acid 110] formed an isolable stable 10-dinitrogen acid 310], while the 6-dinitrogen carboxylate 36](-) reacted in situ, giving products of N-substitution at the B6 position with the heterocyclic solvent (46]). The molecular and crystal structures for pyridinium acid 46]a were determined by X-ray crystallography. The electronic structures and reactivity of the 6-dinitrogen derivatives of the {1-CB(9)} 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.