Ditelluroether complexes of Group 6 metal carbonyls: synthesis, spectroscopic studies and a comparison with dithio- and diseleno-ether analogues

The syntheses of [M(CO)(4)(L-L)] (M = Cr, Mo or W, L-L = MeTe(CH2)(3)TeMe, PhTe(CH2)(3)TePh or o-C6H4(TeMe)(2)) are described along with some dithioether (L-L-MeS(CH2)(2)SMe, MeS(CH2)(3)SMe) and diselenoether (L-L = MeSe(CH2)(2)SeMe, MeSe(CH2)(3)SeMe or o-C6H4(SeMe)(2)) analogues. The complexes have been characterised by IR, H-1-, C-13{H-1}-, Se-77{H-1}-, Te-125{H-1}- and Mo-95-NMR spectroscopy, FAB mass spectrometry and analysis. The structure of [Cr(CO)(4){MeSe(CH2)(2)SeMe}] is reported. Comparison of the spectroscopic data reveals that ditelluroethers are significantly better sigma-donors towards low valent metal centres than their lighter analogues. (C) 1999 Elsevier Science S.A. All rights reserved.