Synthesis and X-ray crystal structures of mixed sandwich Group 8 cyclopentadienyl complexes containing crown trithioether ligands

The syntheses and characterization of three new mixed sandwich complexes in volving crown thioether ligands and Group 8 metal ions are reported. These complexes are: [Ru(C5H5)(9S3)]PF6 (1), [Ru(C5H5)(10S3)]PF6 (2) and [Fe(C5H5 )(10S3)]PF6 (3), where 9S3 = 1,4,7-trithiacyclononane and 10S3 = 1,4,7-trit hiacyclodecane. All three complexes have been characterized by single-cryst al X-ray crystallography, and all structures show an octahedral metal cente r with facially coordinated carbocyclic and macrocyclic ligands. The averag e M-S bond lengths in 1, 2 and 3 are 2.289(2), 2.331(2) and 2.1823(7) Angst rom, respectively, and these are shorter than the MS bond lengths in the co rresponding bis 9S3 and 10S3 complexes. We propose that this distance decre ase is caused by enhanced metal-thioether pi bonding due to the strong sigm a-donating ability of the Cp ligand. All structures are confirmed in soluti on via H-1- and C-13-NMR spectroscopy. Cyclic voltammetric studies on the t hree heteroleptic complexes show E-1/2 values that are intermediate between those of the corresponding homoleptic hexakis(thioether) complexes and met allocenes. This electrochemical behavior is also consistent with the relati ve sigma-donating and pi-accepting abilities of the Cp and trithioether lig ands. (C) 1999 Elsevier Science S.A. All rights reserved.