Symmetric and asymmetric trinuclear cores in novel #mu#-alkoxo-bridged mixed-metal Cu_2~(II)Zn~(II) complexes: synthesis from zerovalent copper and zinc oxide, structure and magnetism

摘要

Three novel heterotrimnuclear complexes, [Cu_2Zn(NH_3)Cl_3(Me_2Ea)_3] 1, [Cu_2Zn(NH_3)Br_3(Me_2Ea)_3] 2 and [Cu_2Zn(NCS)_3(Me_2Ea)_3]·CH_3CN 3 (EA = NCH_2CH_2O), have been prepared using zerovalent copper, zinc oxide, an ammonium salt and 2-dimethylaminoethanol (HMe_2Ea) in air. Crystallographic investigations reveal that they contain trinuclear symmetric (3) and asymmetric (1 and 2) cores, that consist of a portion of a distorted cube in which alternate corners are metal and non-metal atoms and one corner metal site is vacant. The chemical difference between the three compounds produces changes inthe coordination environment of the metal atoms and their overall crystal structures. Crysomagnetic measurements reveal that the overall antiferromagnetic coupling inthe symmetric complex 3 is stronger compared to the other two complexes, despite their slightly shorter copper-copper separations