Isomeric zirconocenophane dichlorides involving two disiloxane-bridged indenyl ligands

Abstract

The title complex 2 = [{O(Me 2SiC 9H 6) 2}ZrCl 2](SiC 9H 6 = 2 silylated indenyl group) has been prepared in a way slightly different from that published recently by Rausch and coworkers ( J. Organomet. Chem., 501 (1995) 375). In contrast to the earlier report, the 1H NMR spectra of 2 in C 6D 6 and CD 2Cl 2 reflect clearly the presence of both rac- 2 and meso- 2 (ca. 4:1). From toluene, 2 crystallizes as a racemic mixture; rac- 2: monoclinic; space group P2√ c, a = 1278.2(4), b = 1196.2(4), c = 1567.8(6) pm; β = 100.8(3)°; R 1 = 0.0314 ( wR 2 = 0.0771). The high-resolution 1H NMR spectrum of rac- 2 does not match with the crystal structure: most probably, rapid (on the NMR time scale) racemization takes place down to at least −80°C.