Dipyridyl β-diketonate complexes and their use as metalloligands in the formation of mixed-metal coordination networks

The iron(III) and aluminium(III) complexes of 1,3-di(4-pyridyl)propane-1,3-dionato (dppd) and 1,3-di(3-pyridyl)propane-1,3-dionato (dmppd), [Fe(dppd)(3)] 1, [Fe(dmppd)(3)] 2, [Al(dppd)(3)] 3 and [Al(dmppd)(3)] 4 have been prepared. These complexes adopt molecular structures in which the metal centres contain distorted octahedral geometries. In contrast, the copper(II) and zinc(II) complexes [Cu(dppd)(2)] 5 and [Zn(dmppd)(2)] 6 both form polymeric structures in which coordination of the pyridyl groups into the axial positions of neighbouring metal centres links discrete square-planar complexes into two-dimensional networks. The europium complex [Eu(dmppd)(2)(H2O)(4)]Cl center dot 2EtOH center dot 0.5H(2)O 7 forms a structure containing discrete cations that are linked into sheets through hydrogen bonds, whereas the lanthanum complex [La(dmppd)(3)(H2O)]center dot 2H(2)O 8 adopts a one-dimensional network structure, connected into sheets by hydrogen bonds. The iron complexes 1 and 2 act as metalloligands in reactions with silver(I) salts, with the nature of the product depending on the counter-ions present. Thus, the reaction between 1 and AgBF4 gave [AgFe(dppd)(3)]BF4 center dot DMSO 9, in which the silver centres link the metalloligands into discrete nanotubes, whereas reactions with AgPF6 and AgSbF6 gave [AgFe(dppd)(3)]PF6 center dot 3.28DMSO 10 and [AgFe(dppd)(3)]SbF6 center dot 1.25DMSO 11, in which the metalloligands are linked into sheets. In all three cases, only four of the six pyridyl groups present on the metalloligands are coordinated. The reaction between 2 and AgNO3 gave [Ag2Fe(dmppd)(3)(ONO2)]NO3 center dot MeCN center dot CH2Cl2 12. Compound 12 adopts a layer structure in which all pyridyl groups are coordinated to silver centres and, in addition, a nitrate ion bridges between two silver centres. A similar structure is adopted by [Ag2Fe(dmppd)(3)(O2CCF3)] CF3CO2 center dot 2MeCN center dot 0.25CH(2)Cl(2) 13, with a bridging trifluoroacetate ion playing the same role as the nitrate ion in 12.