Synthesis and structural behavior of the tris (eta-cyclopentadienyl) zirconium-betaine complex Cp-2[eta(5)-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 conta ins the three g-cyclopentadienide ligands in a nearly trigonal-planar coord ination around zirconium with a pronounced Zr-F-C(aryl) coordination perpen dicular 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 revers ible 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 sp ectroscopy in toluene-d(8).