Copper(II)-diethylenetriamine complexes with monodentate N-donor ligands: Crystal and molecular structure of diethylenetriamine 2-cyanoguanidine copper(II) nitrate

Mixed ligand copper(II) complexes, [Cu(dien)(cnge)X(2) . nH(2)O] (X = NO3-, NO2 or 0.5SO(4)(2-)), containing diethylenetriamine (dien) and cyanoguanidine (cnge), have been prepared and characterized. Similar complexes, [Cu(dien)(ImH)X(2) . nH(2)O] (X = Cl-, NO3-, NO2- or 0.5SO(4)(2-)), containing diethylenetriamine (dien) and imidazole (ImH), were prepared for comparison. Under identical reaction conditions, the corresponding pyridine complexes could not be isolated, the copper(II)-dien complexes, [Cu(dien)X(2) . nH(2)O] (X = Br-, Cl-, NO3-, NO2- or 0.5SO(4)(2-)) being formed. The structure of [Cu(dien)(cnge)(ONO2)(2)] (5) has been determined by single-crystal X-ray diffraction methods. It comprises discrete molecular units based on a tetragonally elongated octahedral copper(II) coordination sphere with equatorially bound dien (average Cu---N = 2.004 Angstrom) and cnge (Cu---N = 1.945 Angstrom) and axially bound, nitrate (Cu---O = 2.517, 2.567 Angstrom). Marked shifts (similar to 25 cm(-1)) to higher frequency in the nu(as) (NCN) band of cnge on coordination to copper(II) in 5 and related complexes are shown to be consistent with strongly bound cnge, as evidenced by short Cu-N distances and near linear CuNC bond angles. FAR-MS studies gave comparable patterns for all complexes, inferring structural types similar to that for [Cu(dien)(cnge)(ONO2)(2)]. Copyright (C) 1996 Elsevier Science Ltd