Higher valent metal pentadienyl chemistry : Syntheses, structures, and reactions of Zr(6,6-dmch)2X2 complexes (dmch = dimethylcyclohexadienyl; X = Cl, Br, I) and related species

The zirconium(II) complex Zr(6,6-dmch) 2 (PMe 3 ) 2 undergoes facile reactions with 1,2-dihaloalkanes, yielding the formal oxidative addition products Zr(6,6-dmch) 2 X 2 (X = Cl, Br, I). A similar reaction with 1-chloro-2-methoxyethane yields Zr(6,6-dmch)2(Cl)(OCH3). Each of the complexes has been characterized analytically, spectroscopically, and structurally. A direct oxidative addition reaction occurs with CH 3 Br, yielding the thermally unstable Zr(6,6-dmch)2(CH3)(Br), which has been characterized spectroscopically and structurally. As had been observed for related Zr(C 5 H 5 )(6,6-dmch)X 2 complexes, the Zr-dmch coordination is severely skewed, with quite short Zr-C3 interactions and substantially lengthened interactions with the remaining carbon atoms of the dienyl fragment. This may be attributed to an inability of the contracted Zr(IV) orbitals to interact effectively with all the carbon atoms in the wide, electronically open dienyl ligands.