A phosphorus-supported multisite coordination ligand containing three imidazolyl arms and its metalation behaviour. An unprecedented co-existence of mononuclear and macrocyclic dinuclear Zn(ii) complexes in the same unit cell of a crystalline lattice.

The reaction of (S)P[N(Me)NH(2)](3) with three equivalents of 4(5)-imidazolecarboxaldehyde afforded, in situ, (S)P[N(Me)N[double bond, length as m-dash]CHIm](3) (Im = imidazolyl). The reaction of the latter with metal salts afforded mononuclear complexes [{(S)P[N(Me)N[double bond, length as m-dash]CHIm](3).M}][X](2) [M = Co, X = NO(3); M = Ni, X = ClO(4); M = Cd, X = NO(3)]. In these compounds, in the cationic part, the metal ion is bound by three imino and three imidazolyl nitrogen atoms to generate a trigonal prismatic type of coordination environment. Structural analysis of the zinc complex showed the presence of a mononuclear [{(S)P[N(Me)N[double bond, length as m-dash]CHIm](3).Zn}][NO(3)](2) and a dinuclear 20-membered metallamacrocycle [{(S)P[N(Me)N[double bond, length as m-dash]CHIm](3).Zn}(2)][NO(3)](4) in the same unit cell. Solution studies of the zinc complex revealed a monomer-macrocycle equilibrium.