C-donor lariat ether 'scorpionates'

Structural studies on a range of Ag+ and Pb2+ complexes of N-allyl and N-butenyl lariat ethers are reported. In the case of smaller ligands with allyl side arms (L = N-allylaza-15-crown-5 and N-azaallyl-18-crown-6), coordination polymers of type [Ag(L)](+)(infinity) exhibiting Ag+...pi interactions are observed. Increasing the length of the side arm to N-butenylaza-18-crown-6 gives a monomeric 'scorpionate' species in which the Ag+ ion is simultaneously bound to the macrocyclic portion and side arm of a single ligand. NMR titration results indicate that the Ag+...pi interactions persist in solution. In the case of Pb2+ complexes no side arm involvement is observed in any case. The novel protonated complex (H3O) (N-allylaza-18-crown-6) [Cu2I3] is also reported.