Nitrogen-containing cyclic ligands

DETAILED DESCRIPTION We claim: 1.
A ligand having the formula: ##STR44## in which R.
sub.
1 represents a radical of the formula: ##STR45## R.
sub.
6 being selected from the group consisting of C.
sub.
1 -C.
sub.
18 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl, C.
sub.
1 -C.
sub.
6 polyhydroxyalkyl and a group of the formula: ##STR46## R.
sub.
11 being selected from the group consisting of C.
sub.
1 -C.
sub.
8 alkylene, R.
sub.
7 being selected from the group consisting of hydrogen, C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl and C.
sub.
1 -C.
sub.
6 polyhydroxyalkyl, m=0 or 1, R.
sub.
2, R.
sub.
3, R.
sub.
4, identical or different represent a radical of the formula ##STR47## R.
sub.
8 and R.
sub.
9, identical or different, being selected from hydrogen, C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl and C.
sub.
1 -C.
sub.
6 polyhydroxyalkyl, p=1 or 2, n=0, 1 or 2 and R.
sub.
5 is selected from the group consisting of hydrogen, C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl and C.
sub.
1 -C.
sub.
6 polyhydroxyalkyl, and Z is selected from the group consisting of oxygen and a group of the formula: >N--R.
sub.
10 R.
sub.
10 being selected from the group consisting of hydrogen, C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl, C.
sub.
1 -C.
sub.
4 polyhydroxyalkyl, a group of the formula ##STR48## R.
sub.
5 having the meaning given previously R.
sub.
13, R.
sub.
14, R.
sub.
15 and R.
sub.
16, identical or different being selected from the group consisting of hydroxy and a group of the formula ##STR49## R.
sub.
17 and R.
sub.
18, identical or different being selected from the group consisting of hydrogen, C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
6 hydroxyalkyl and C.
sub.
1 -C.
sub.
6 polyhydroxyalkyl, as well as salts thereof.
2.
A ligand of the formula: ##STR50## in which R.
sub.
1 represents a radical of the formula: ##STR51## R.
sub.
6 being selected from the group consisting of C.
sub.
1 -C.
sub.
14 alkyl, C.
sub.
1 -C.
sub.
4 hydroxyalkyl, C.
sub.
1 -C.
sub.
4 polyhydroxyalkyl and a group of the formula: ##STR52## R.
sub.
11 being selected from the group consisting of C