Synthesis and crystal structure of an ansa-disilylene-bridged zirconocene complex

Reaction of lithiated 1,1',2,2'-tetramethyl-disilyl-1,2-bis[2-(4,5,6,7,8-pe ntahydro)-azulene] (1) with ZrCl4 in THF at -78 degreesC gave the new {1,1' ,2,2'-tetramethyl-disilyl-1,2-bis[2-(4,5,6,7,8-pentahydro)-azulenyl]}zircon ium dichloride complex (II) in reasonable yield. It crystallizes in the ort horhombic Pnma space group with a = 19.792(4), b = 18.493(3), c = 7.105(1) Angstrom and Z = 4. The complex (II) is symmetric with respect to a mirror plane passing through the Zr and the two Cl atoms. The coordination geometr y of Zr atom is that of a distorted tetrahedron formed by the two Cl atoms and the centroids of the two cyclopentadienyl rings of the pentahydroazulen yl moieties. The Zr-Cl bond lengths are 2.451(2) and 2.419(2) Angstrom and the Zr-C distances vary in the range 2.437(4)-2.588(4) Angstrom.