SYNTHESIS, SPECTROSCOPIC AND STRUCTURAL CHARACTERIZATION OF THE FIRSTMIXED FLUORO-BROMO GROUP-4 ORGANOMETALLIC COMPLEX [(CP-ASTERISK-ZRF2BR)(4)] (CP-ASTERISK=C(5)ME(5))

[{CpZrF2Br}(4)] is conveniently prepared in high yield from the react ion of [{CpZrF3}(4)] with four equivalents of Me(3)SiBr. In contrast the reaction of [{CpZrF3}4] with Me(3)SiI under identical reaction co nditions leads to a mixture of [CpZrI3] and unreacted [{Cp*ZrF3}(4)]. The crystal structure of [{CpZrF2Br}(4)] has been determined by X-ra y diffraction studies. The compound crystallizes in the orthorhombic c rystal system [a = 9.325(1), b = 23.483(3), c = 27.016(5) Angstrom, al pha = beta = gamma = 90 degrees, space group Ibam, Z = 4]. The tetrame ric core structure of [{CpZrF2Br}(4)] contains four zirconium atoms l inked by alternating single and triple fluorine bridges. One terminal bromine atom is bonded to each zirconium. H-1 and F-19-NMR spectroscop ic data and structural features of the title compound are compared wit h those for the mixed fluoro-chloro complexes [{CpZrF2Cl}(4)], [{Cp*Z rF2Cl}(2){CpZrFCl2}(2)] and the trifluoro complex [{Cp*ZrF3}(4)].