Metallacycles of iron, zinc, and cadmium assembled by polytopic bis(pyrazolyl)methane ligands and fluoride abstraction from BF4-

Reactions of the arene-linked bis(pyrazolyl)methane ligands m-bisbis(1-pyrazolyl)methyl]benzene (m-CH(pz)2]2C6H4, Lm) and 1,3,5-trisbis(1-pyrazolyl)methyl]benzene (1,3,5-CH(pz)2]3C6H3, L3) with BF4- salts of divalent iron, zinc, and cadmium result in fluoride abstraction from BF4- and formation of fluoride-bridged metallacyclic complexes. Treatment of Fe(BF4)2.6H2O and Zn(BF4)2.5H2O with Lm leads to the complexes Fe2(mu-F)(mu-Lm)2](BF4)3 (1) and Zn2(mu-F)(mu-Lm)2](BF4)3 (2), in which a single fluoride ligand and two Lm molecules bridge the two metal centers. The reaction of Cd2(thf)5](BF4)4 with Lm results in the complex Cd2(mu-F)2(mu-Lm)2](BF4)2 (3), which contains dimeric cations in which two fluoride and two Lm ligands bridge the cadmium centers. Equimolar amounts of the tritopic ligand L3 and Zn(BF4)2.5H2O react to give the related monofluoride-bridged complex Zn2(mu-F)(mu-L3)2](BF4)3 (4), in which one bis(pyrazolyl)methane unit on each ligand remains unbound. NMR spectroscopic studies show that in acetonitrile the zinc metallacycles observed in the solid-state remain intact in solution.