Symmetrical and unsymmetrical polyalkylamine metal complexes for ligand extraction and generation

An improved process to produce an unsymmetrical prechelate compound of Structure I:

• ##STR42## or a salt thereof, wherein R.sup.1 and R.sup.2 are each independently selected from aliphatic, alicyclic, or aromatic organic compounds each containing at least one nitrogen atom which is suitable for coordination to a transition metal ion, with the proviso that R.sup.1 and R.sup.2 are each independently different chemical groups containing an aromatic nitrogen atom,
• R.sup.3 and R.sup.4 are each independently --H,
• a and b are each 0,
• d and q are each independently selected from 1, 2, 3, 4 or 5 and d=q, which process comprises:
• (a) contacting about one equivalent a compound of the structure:
• H.sub.2 N--(CH.sub.2).sub.d --NH--(CH.sub.2).sub.q NH.sub.2
• with about one equivalent of R.sup.1 --(CH.sub.2).sub.a (C.dbd.O)R.sup.3 where R.sup.1, R.sup.3, a, d and q are defined above, in an anhydrous organic solvent capable of forming an azeotrope with water and either molecular sieves or under elevated temperature reflux and azeotropic conditions sufficient to remove water and to produce a compound of Structure II;
• ##STR43## (b) contacting the product of step (a) with about one equivalent of R.sub.2 --(CH.sub.2).sub.b (C.dbd.O)R.sup.4, wherein b, R.sup.2 and R.sup.4 are defined hereinabove in an anhydrous organic solvent capable of forming an azeotrope with water and either with molecular sieves or under elevated temperature reflux and azeotropic conditions effective to essentially remove all of the water produced by condensation;
• (c) removing the organic solvent to isolate the imine intermediate;
• (d) contacting the imine intermediate with a second anhydrous organic solvent under hydride reducing conditions effective to selectively reduce the imine;
• and
• (e) recovering the compound of structure (I).

An organic compound of the general structure (I):

• ##STR44## wherein R.sup.1 and R.sup.2 are each independently selected from aliphatic, alicyclic, or aromatic organic groups which contain at least one nitrogen, or sulfur, or oxygen atom which is suitable for coordination to a transition metal ion, with the proviso that R.sup.1 and R.sup.2 are the same or different chemical groups;
• a and b are each independently 0, 1 or 2;
• R.sup.3 and R.sup.4 are each independently --H or --CH.sub.3 ;and
• d and q are each independently selected from 1, 2, 3, 4 or 5.