Anionic carbonato and oxalato cobalt(iii) nitrogen mustard complexes

Abstract

Synthetic approaches to cobalt(III) complexes [Co(L)(L′)₂] containing the bidentate dialkylating nitrogen mustard N,N-bis(2-chloroethyl)-1,2-ethanediamine (L = dce) together with anionic ancilliary ligands (L′) which are either carbonato (CO₃²⁻), oxalato (ox²⁻), bis(2-hydroxyethyl)dithiocarbamato (bhedtc⁻), 2-pyridine carboxylato (pico⁻) or 2-pyrazine carboxylato (pyzc⁻) were investigated. Synthetic routes were developed using the related amines N,N-diethyl-1,2-ethanediamine (dee) and 1,2-ethanediamine (en). The complexes [Co(CO₃)₂(L)]⁻ (L = dee 1, dce 2), [Co(ox)₂(L)]⁻ (L = dee 3, dce 4), [Co(bhedtc)₂(dee)]⁺5, [Co(bhedtc)₂(en)]⁺6, mer-[Co(pico)₃], mer-[Co(pyzc)]₃7 and [Co(pico)₂(dee)]⁺8 were prepared and were characterised by IR, UV-Vis, ¹H and ¹³C{¹H} NMR spectroscopy, mass spectrometry and cyclic voltammetry. [Co(bhedtc)₂(en)]BPh₄6b and trans(O)-[Co(pico)₂(dee)]ClO₄8 were characterised by X-ray crystallography. In vitro biological tests were carried out on complexes 1–4 in order to assess the degree to which coordination of the mustard to cobalt attenuated its cytotoxicity, and the differential toxicity in air vs. nitrogen.