Synthesis and structural behavior of the tris (η-cyclopentadienyl) zirconium-betaine complex Cp2[η5-C5H4B(C6F5)3]Zr

Treatment of the reagent [C5H4B(C6F5)(3)]Na,Li . Et2O (4) With zirconocene dichloride gave the neutral tris(cyclopentadienyl)Zr-betaine-type complex (eta (5)-Cp)(2)[eta (5)-C5H4B(C6F5)(3)]Zr (1) In the crystal complex 1 contains the three g-cyclopentadienide ligands in a nearly trigonal-planar coordination around zirconium with a pronounced Zr-F-C(aryl) coordination perpendicular to it. The Zr-F bond length is 2.310(3) Angstrom. The Zr-F-C(aryl) coordination is persistent in solution. The activation energy of the reversible cleavage of the Zr-F linkage of 1 was determined as DeltaG((Zr-F)diss)(double dagger)(253 K) = 10.2 +/- 0.2 kcal mol(-1) ' by dynamic F-19 NMR spectroscopy in toluene-d(8).