NEW DEVELOPMENTS IN THE CHEMISTRY OF HETEROPOLYTUNGSTATES OF RHODIUM AND CERIUM

The heteropolytungstates [PW11O39RhCl](5-) (I), [PW11O39RhCH2COOH](5-) (III), and [PW11O39{Rh-2(OAcD)(2)](5-) (IV) are prepared by hydrother mal reaction of [PW11O39](7-) with RhCl3 or Rh-2(OAc)(4) and character ized by NMR and X-ray structure determination. Electrolytic reduction of I yields the dimeric species [(PW11O39Rh2)](10-) (II) which reacts with C6H5CH2Br under photochemical conditions to yield dibenzyl and [P W11O39RhBr](5-) in a process analogous to Rh-porphyrins. Anion III and the corresponding Si-centered anion are rare examples of complexes wi th Rh-C bonds prepared in aqueous solution. Reaction of B-alpha-[(AsW9 O33)-W-III](9-) with Ln(III) yields new, massive heteropolytungstates [As(2)Ln(2)(H2O)W29O103](17-); Ln = La, Ce (V), Ce-4(H2O)(4-4x)(AsW9O3 3)(4)As(WO3)(2+x)(WO5)](25-) < 0.5 (VI), and As(12)Ln(16)(H2O)(36)W184 O324](76-); Ln = La,Ce (VII) with approximate relative molecular masse s of 7 600, 10 500, and 40 000 respectively. Anion VII has a folded cy clic structure with a radius of 4 nm and is the largest heteropolytung state so far reported. It is synthesized in yields of ca 30 % under mi ld conditions. (C) Academie des Sciences/Elsevier, Paris.