Hydrogen-bonding interactions in the series of complexes [M(C4O4)(OH2)(2)(dmf)(2)] and [M(C4O4)(OH2)(4)] (M = Mn, Co, Ni, Cu, Zn)

Reaction of tetrabutylammonium aminosquarate (1-amino-2-methoxycyclobutened ionate) with MCl2. xH(2)O (M = Mn, Co) and tetraethylammonium aminosquarate with M(NO3)(2). xH(2)O (M = Ni, Cu, Zn) in N,N-dimethyl-formamide (dmf) af forded the series of complexes M(C4O4)(OH2)(2)(dmf)(2). The complexes are i somorphous and crystallise in the space group P2(1)/c, with the exception o f the copper analogue which crystallises in P2(1)/n. They all have chain st ructures that are similar to the squarates [M(C4O4)(OH2)(4)] and the comple xes [Zn(C4O4)(OH2)(2)(dmso)(2)] and [Ni(C4O4)(C3N2H4)(2)(OH2)(2)] and exhib it similar but subtly different hydrogen-bonding interactions to those obse rved in [Zn(C4O4)(OH2)(2)(dmso)(2)]. Analysis of the hydrogen-bonding inter actions in these complexes provides an insight into some additional factors that affect these interactions in transition metal squarates and their rol e in determining tertiary structure. The implications with respect to solid -state materials design are discussed.