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-bis[bis(1-pyrazolyl)methyl]benzene (m-[CH(pz)(2)](2)C6H4, L-m) and 1,3,5-tris[bis(1-pyrazolyl)methyl] benzene (1,3,5-[CH(pz)(2)](3)C6H3, L-3) 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).6H(2)O and Zn(BF4)(2).5H(2)O with L-m leads to the complexes [Fe-2(mu-F)(mu-L-m)(2)](BF4)(3) (1) and [Zn-2(mu-F)(mu-L-m)(2)](BF4)(3) (2), in which a single fluoride ligand and two L-m molecules bridge the two metal centers. The reaction of [Cd-2(thf)(5)](BF4)(4) with L-m results in the complex [Cd-2(mu-F)(2)(mu-L-m)(2)](BF4)(2) (3), which contains dimeric cations in which two fluoride and two L-m ligands bridge the cadmium centers. Equimolar amounts of the tritopic ligand L-3 and Zn(BF4)(2).5H(2)O react to give the related monofluoride-bridged complex [Zn-2(mu-F)(mu-L-3)(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.