title: Confirmation of the semivacant Wells-Dawson polyoxotungstate skeleton. The structures of [Ce{X(H4)W17O61}2]19- (X = P, As) indicate the probable location of internal protons.
abstract: Reaction of Ce(III) with lacunary versions of [H(4)XW(18)O(62)](7-) (X = P, As) yields the 1:2 complexes [Ce(H(4)XW(17)O(61)](19-) (X = As, 1; P, 2) in good yield, characterized in solution and the solid state by NMR spectroscopy and X-ray crystallographic analysis, respectively. The structures confirm a syn C(2) conformation that is analogous to that observed for [Ln(alpha(2)-P(2)W(17)O(61))(2)](17-) but with "empty" O(4) tetrahedra that are in positions remote from the cerium atom. Bond valence sum calculations for these structures show that the four protons that are required for charge balance in all salts of the XW(18) anions and their lacunary derivatives are almost certainly bound to the oxygen atoms of the empty tetrahedra.
authors.affiliation: Chemistry Department, Georgetown University, Washington, D.C., 20057-1227, USA.
authors.forename: Nebebech
authors.initials: N
authors.lastname: Belai
authors.forename: Michael H
authors.initials: MH
authors.lastname: Dickman
authors.forename: Michael T
authors.initials: MT
authors.lastname: Pope
authors.forename: Roland
authors.initials: R
authors.lastname: Contant
authors.forename: Bineta
authors.initials: B
authors.lastname: Keita
authors.forename: Israel-Martyr
authors.initials: IM
authors.lastname: Mbomekalle
authors.forename: Louis
authors.initials: L
authors.lastname: Nadjo