Synthesis of the Quatercyclopentadienyl Ligand and Its Half-Sandwich Tetratungsten Complexes

Abstract

Double 3-oxocyclopentenylation of the fulvalene dianion, followed by metalation, results in the four isomeric bis(enones) 1 which were elaborated via the bis(cyclopentadienes) 2 to the four regio- and stereoisomeric forms of (quatercyclopentadienyl)tetratungsten (connectivity 1,1`,2`,1,3, 1` (3a,b and 4a,b) and 1, 1`,3`,1,3,1` (3c,d and 4c,d)). The molecular structures of 1a and 1b have been determined by X-ray analysis. The tetramethyl complex 5 is obtained from 2d by a metalation-methylation sequence involving deprotonation of the intermediate bis(tungsten hydride) with K{sup +}(-OC(CH{sub 3}{sub 3}). 14 refs., 2 figs.