Lipophilic halogenozirconocene( III ) complexes: [{Zr[η-C 5 H 3 (SiMe 3 ) 2 -1,3] 2 (µ-Cl)} 2 ], [NBu n 4 ][Zr{η-C 5 H 3 (SiMe 3 ) 2 -1,3} 2 Cl 2 ] and [Zr{η-C 5 H 3 (SiMe 3 ) 2 -1,3} 2 Cl 2 ]

Treatment of [Zr{η-C5H3(SiMe3)2-1,3}2X2] with Na–Hg in tetrahydrofuran (THF) affords the blue (X = Cl 2a or Br) or green (X = I) crystalline complexes [{Zr[η-C5H3(SiMe3)2-1,3]2(µ-X)}2], with characteristic ZrIII ESR spectra (PhMe, 300 K) and exceptionally long (3.86–4.17 Å) Zr ⋯ Zr contacts; 2a is susceptible to facile Zr(µ-Cl)2Zr bridge-cleavage upon reaction with either a neutral (e.g. THF) or an anionic (e.g. Cl–) nucleophile, as in its conversion into [NBun4][Zr{η-C5H3(SiMe3)2-1,3}2Cl2].