Design of base metal extractants. Part 1. Inter-ligand hydrogen bonding in the assembly of pseudo-macrocyclic bis(aminosulfonamidato)M(II) complexes.
Monosulfonyl derivatives of simple 1,2- and 1,3-diamines (R2HN-R-NHSO2R1 = L) have been shown to be easily deprotonated to give neutral 2:1 complexes, [M(L - H)(2)], with Co(II), Ni(II), Cu(II) or Zn(II). The Ni(II) and Cu(II) complexes with deprotonated N-tosyl-1,2-diaminoethane have a planar N4(2-) donor set and a 14-membered pseudo-macrocyclic structure based on head-to-tail S=O...H-N((amine)) bonding between the two bidentate ligands. In the related tetrahedral Zn(II) complex the ends of the mutually perpendicular bidentate N2- units are too far apart to form a cyclic H-bonded system. X-Ray structure determinations on five free ligands provide evidence for extensive inter-molecular H-bonding, which in the case of N-tosyl-1,3-diaminopropane and its N'-tert-butyl derivative involves formation of dimeric 16-membered pseudo-macrocycles. Despite favourable inter-ligand H-bonding in the neutral 2:1 complexes, these ligands are relatively weak extractants, showing >50% loading of Cu(II) in "pH-swing" equilibria, 2L(org)+ M2+ = [M(L - H)2](org)+ 2 H+, only when the pH of the aqueous phase is raised above 4.
Squires
Clare
C
School of Chemistry, University of Edinburgh, Edinburgh, UK.
Baxter
Christopher W
CW
Campbell
John
J
Lindoy
Leonard F
LF
McNab
Hamish
H
Parkin
Andrew
A
Parsons
Simon
S
Tasker
Peter A
PA
Wei
Gang
G
White
David J
DJ
D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry*
D008024:Ligands; D047028:Macrocyclic Compounds; D019216:Metals, Heavy; D009942:Organometallic Compounds; D013449:Sulfonamides