New developments in the chemistry of heteropolytungstates of rhodium and cerium

Abstract The heteropolytungstates [PW 11 O 39 RhCl] 5− (I), [PW 11 O 39 RhCH 2 COOH] 5− (III), and [PW 11 O 39 Rh 2 (OAc) 2 ] 5− (IV) are prepared by hydrothermal reaction of [PW 11 O 39 ] 7− with RhCl 3 or Rh 2 (OAc) 4 and characterized by NMR and X-ray structure determination. Electrolytic reduction of I yields the dimeric species [(PW 11 O 39 Rh 2 )] 10− (II) which reacts with C 6 H 5 CH 2 Br under photochemical conditions to yield dibenzyl and [PW 11 O 39 RhBr] 5− in a process analogous to Rh-porphyrins. Anion III and the corresponding Sicentered anion are rare examples of complexes with Rh-C bonds prepared in aqueous solution. Reaction of B-α [As III W 9 O 33 ] 9− with Ln III yields new, massive heteropolytungstates [As 2 Ln 2 (H 2 O)W 29 O 103 ] 17− Ln = La, Ce(V), [Ce 4 (H 2 O) 4 − 4 x (AsW 9 O 33 ) 4 As(WO 3 ) 2 + x (WO 5 )] 25− , x 12 Ln 16 (H 2 O) 36 W 184 O 324 ] 76− ; Ln La,Ce (VII) with approximate relative molecular masses of 7 600, 10 500, and 40 000 respectively. Anion VII has a folded cyclic structure with a radius of 4 nm and is the largest heteropolytungstate so far reported. It is synthesized in yields of ca 30 % under mild conditions.