Condensation Reactions of Cobalt Amino Acid Complexes with Formaldehyde: Preparation and Crystal Structures of Cobalt Complexes Containing New Hexadentate, Pendant-Arm Macrocyclic and Acyclic Ligands

The reaction of cobalt(III) complexes α- cis -[Co(EDDA)L] + containing both amino acid (EDDA, ethylenediamine- N, N ‘-diacetate) and bidentate amine ligands (L = en, ethylenediamine; Men, N -methylethylenediamine; BEE, N, N ‘-diethylethylenediamine; DEE, N, N -diethylethylenediamine) with formaldehyde under basic conditions has been investigated. For L = en, the product is [Co(L 1 )] +, which contains a macrocyclic ligand (L 1 = 1,4-bis(carboxymethyl)-6,13-dioxacyclam) formed by linking the primary nitrogens on the en ligand with the secondary nitrogens on the EDDA ligand through two CH 2 OCH 2 bridges. For L = Men and DEE, which each contain only one primary nitrogen, the reaction gives complexes [Co(L 2 )] + and [Co(L 3 )] + bearing hexadentate acyclic ligands (L 2 = 1,4-bis(carboxymethyl)-11-ethyl-6-oxa-1,4,8,11-tetraazatridecane; L 3 = 1,4-bis(carboxymethyl)-6-oxa-1,4,8,11-tetraazadodecane) each resulting from formation of one new CH 2 OCH 2 linkage. All complexes have been characterized by 1 H and 13 C NMR, IR, and UV−visible spectroscopy and cyclic voltammetry. The X-ray crystal structures of [Co(L 1 )]Cl·3H 2 O and [Co(L 3 )]PF 6 ·NH 4 PF 6 ·H 2 O have been determined. [Co(L 1 )]Cl·3H 2 O is monoclinic, P 2 1 / n, with a = 14.792(3) Å, b = 7.766(1) Å, c = 16.520(4) Å, β = 99.54(2)°, V = 1871.5(6) Å 3, Z = 4, R = 0.042. [Co(L 3 )]PF 6 ·NH 4 PF 6 ·H 2 O is monoclinic, P 2 1 / n, with a = 13.353(6) Å, b = 11.595(2) Å, c = 16.900(5) Å, β = 95.59(3)°, V = 2604(2) Å 3, Z = 4, R = 0.107.