PI-H3C5(ME2SI)(ME2SISIME2)-PI-C5H3 - A NOVEL AND SIMPLE DOUBLE-BRIDGED DICYCLOPENTADIENYL LIGAND - SYNTHESIS AND EXAMPLE OF ITS APPLICATIONIN THE CHEMISTRY OF COMPLEXES

Deprotonation of dicyclopentadienyldimethylsilane with two equivalents of n-butyllithium and subsequent reaction with 1,2-dichlorotetramethy ldisilane yields the double-bridged dicyclopentadiene H4C5(SiMe2)(Si2M e4)C5H4 (1 = H2L). Reaction of 1 with two equivalents of n-butyllithiu m leads to the dilithio compound Li-2 [H3C5(SiMe2)(Si2Me4)C5H3] (2 = L i2L) with the bridging dimethylsilyl and tetramethyldisilanyl group in 1,2 position (ortho-position) at each cyclopentadienyl unit 2 is used as starting material for the exemplary synthesis of the following met al complexes: Cp '' Cl2ZrLZrCl2Cp '' (3; Cp '' = 1,3-(t-Bu)(2)C5H3), C p '' Cl2ZrLH (4); Me5C5RuLRuC5Me5 (syn: 5a; anti: 5b); syn-(CO)(2)CoLC o(CO)(2) (6). All compounds are characterized by spectroscopic and ana lytical data. X-ray crystal structures are presented for 1 and for 3. Stereochemical effects in metal complexes with the new unsymmetrically bridged dicyclopentadienyl ligand L are discussed.