The [Cu_2(O_2CMe)_4(btd)_2] complex as a bridging unit:preparation,characterisation,X-ray structure and magnetism of the 2D coordination polymer {[Cu_6(O_2CMe)_8(OMe)_4(btd)_2]}_n (btd=2,1,3-benzothiadiazole)

摘要

A systematic investigation of the Cu_2(O_2CMe)_4(H_2O)_2]/btd reaction sysem is described,where btd=2,1,3-benzothiadiazole.Reaction of [Cu_2(O_2CMe)_4(h_2o)_2] with 5-8 equiv.of btd in both MeCN and MeOH yields [Cu_2(O_2CMe)_4(btd)_2] (1) 40-50% yields.Treatment of [Cu_2(O_2CMe)_4(H_2O)_2] with 1.4 or 0.7 equiv.of btd in MeOHleads to the precipitation of the polymeric compound {[Cu_6(O_2CMe)_8(OMe)_4(btd)_2]} (2) in 82% yield.Reaction of 1 with two equivalents of [Cu_2(O_2CMe)_4(H_2O)_2] in MeOH under reflux provides an additionalroute to 2.The structure of 1 consists of centrosymmetric dinuclear [Cu_2(O_2CMe)_4(btd)_2] molecules of the paddle-wheel cage type.The two Cu~(II) ions are bridged by four #eta#~1:#eta#~:#mu#_2 acetates,while a monodentate btd is at the apex of the square pyramid of each metal centre.The 2D structure of 2 consists of chains of tetranuclear,planar Cu_4(OMe)_4(O_2CMe)_4 repeating units running along the #alpha# axis,which are connected along the cell body diagonal via Cu_2(O_2CMe)_4(btd) paddle-wheel dinuclear units.The btd moelcules behave as bidentate bridging ligands.Within the tetranuclear units,each Cu~(II) ion is connected via two acetate bridges with one neighbouring Cu~(II) ion;intertetranuclear linking is provided by two monoatomic acetate bridges.The results of solid state magnetic susceptibility studies are described for complex 2 in the temperature range 3-300K.The results reveal antiferromagnetic exchange interactions between the Cu~(II0 ions.The complicated structure of 2 does not permit an exact treatment for the determination of the various exchange interactions.However,an approximate 3-J magnetic model was constructed,resulting in an excellent fit.An oirbital interpretation of theJ-trend derived is also attempted.