Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)

The thermal decarbonylation of (Ring)WX3(CO)(2) in refluxing toluene has le d to the preparation of the CO-free compounds [(Ring)WX3](2) [Ring = eta(5) -C5H5 (Cp) and X = Cl (1a) or Br (1b); Ring = eta(5)-C5H4Me (Cp'), X = Cl ( 2a) or Br (2b); Ring = eta(5)-C5Me5 (Cp*), X = Cl (3)]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a different structure from that of the paramagnetic molybdenum analogues. Com pounds la and la react with dppe to afford mononuclear 18-electron adducts, (Ring)WCl3(dppe) (Ring = Cp (4) or Cp' (5)). The X-ray structure of 5 show s a pseudo-fac-octahedral geometry with the dppe ligand occupying two equat orial (e.g. cis relative to Cp') coordination sites. The X-ray structure of two by-products of the synthetic processes are also reported, e.g. Cp-3'W3 Cl3(mu(2)-Cl)(2)(mu(3)-O) (6) and [Cp*WCl3](2)(mu-O) (7). (C) 2000 Elsevier Science S.A. All rights reserved.