CHROMIUM(III) COMPLEXES OF POLYDENTATE AND MACROCYCLIC SELENOETHERS-SYNTHESIS, SPECTROSCOPIC AND EXAFS STUDIES

The reaction of [CrX3(thf)(3)] (X = Cl or Br) with the isomeric trisel enoethers MeC(CH2SeMe)(3) and Se(CH2CH2CH2SeMe)(2) (L) forms the very moisture sensitive [CrX3L] complexes. The macrocycle [16]aneSe(4) (1,5 ,9,13-tetraselenacyclohexadecane) forms [CrX2([16]aneSe(4))]PF6. The c omplexes have been characterized by analysis, IR and UV-visible spectr oscopy and electrospray mass spectrometry. The UV-visible spectra have been analysed and the low 10Dq and large B values, are consistent wit h weak binding of the soft selenium ligands to the hard Cr-III. Chromi um K-edge EXAFS data has been recorded and analysed for the chromium c hloride complexes to produce Cr-Se and Cr-Cl distances, which provide further strong evidence for weak Cr-III-selenoether interactions. (C) 1997 Elsevier Science Ltd.