Well-defined adducts of triethyl thiophosphate with some metal perchlorates

Adducts of triethyl thiophosphate (L) with various metal perchlorates were synthesized under relatively mild preparative conditions (owing to the tendency of these adducts to decompose, yielding the corresponding diethyl thiophosphato metal complexes and ethyl perchlorate). Among a series of new adducts isolated, those with Ni2+ and Cu2+ perchlorates were too unstable for characterization, but in the rest of the cases investigated (Mn+  Al3+, Cr3+, Fe3+, Co2+, Zn2+, Cd2+, Hg2+, Ag+) the adducts were sufficiently stable. The free ligand exists in the thione tautomeric form ((C2H5O)3PS), which is retained in most of its soft or borderline metal ion complexes, i.e. [ML4(OClO3)](ClO4) (M  Co, Zn), [CdL4](ClO4)2 and [AgL2] (ClO4): all these compounds contain PS sulfur-bonded L groups. On the other hand, L undergoes tautomerization, coordinating through the PO oxygen of the thiol isomeric form ((C2H5O)2(C2H5S)PO) in the corresponding complexes with hard metal ions, viz. [ML4(OClO3)2](ClO4) (M = Al, Fe) and (CrL2(OH2)2(OClO3)2](ClO4). The new [HgL4](ClO4)2 complex is rather unusual, for a L complex with a soft metal ion, in that it seems to contain both PS S-bonded triethyl phosphorothionate and PO O-bonded triethyl phosphorothiolate ligands. Possible reasons for this anomaly are discussed.