TY - JOUR
T1 - Bis-hypodentate coordination in a classical Werner-type complex
T2 - Synthesis and structure of [Co(en-N,N)2(enH-N)2]Br5·H2O
AU - Cordes, David B.
AU - Tarak, Ryan R.
AU - McDonald, Shay M.
AU - Cameron, Scott A.
AU - Clarke, Charles R.
AU - Blackman, Allan G.
PY - 2013/3
Y1 - 2013/3
N2 - The synthesis, characterisation (elemental analysis, 1H and 13C NMR, UV–Vis), X-ray crystal structure and pKa values of the bis-hypodentate complex cis-[Co(en-N,N')2(enH-N)2]Br5·H2O are reported. Reaction of cis-[Co(en-N,N')2Cl2]+ in neat ethylenediamine for 1 min followed by acid quenching and cation exchange chromatography gives cis-[Co(en-N,N')2(enH-N)2]Br5·H2O on crystallisation of the product from water containing added LiBr. X-ray structural characterisation of the complex as the dihydrate confirms both the presence of two hypodentate ethylenediamine ligands protonated at the terminal N atoms, and their cis disposition. The complex displays pKa values of 7.36 ± 0.06 and 7.96 ± 0.06 (I = 1.0 M, NaClO4), and undergoes base hydrolysis to give cis-[Co(en-N,N')2(OH)2]+ over the [OH-] range 0.10–0.50 M. No evidence for the formation of [Co(en-N,N')3]3+ in this reaction was obtained.
AB - The synthesis, characterisation (elemental analysis, 1H and 13C NMR, UV–Vis), X-ray crystal structure and pKa values of the bis-hypodentate complex cis-[Co(en-N,N')2(enH-N)2]Br5·H2O are reported. Reaction of cis-[Co(en-N,N')2Cl2]+ in neat ethylenediamine for 1 min followed by acid quenching and cation exchange chromatography gives cis-[Co(en-N,N')2(enH-N)2]Br5·H2O on crystallisation of the product from water containing added LiBr. X-ray structural characterisation of the complex as the dihydrate confirms both the presence of two hypodentate ethylenediamine ligands protonated at the terminal N atoms, and their cis disposition. The complex displays pKa values of 7.36 ± 0.06 and 7.96 ± 0.06 (I = 1.0 M, NaClO4), and undergoes base hydrolysis to give cis-[Co(en-N,N')2(OH)2]+ over the [OH-] range 0.10–0.50 M. No evidence for the formation of [Co(en-N,N')3]3+ in this reaction was obtained.
U2 - 10.1016/j.poly.2012.06.037
DO - 10.1016/j.poly.2012.06.037
M3 - Article
SN - 0277-5387
VL - 52
SP - 1227
EP - 1230
JO - Polyhedron
JF - Polyhedron
ER -