Frédéric Favier

Conformational preferences and protonation sequence of myo-inositol hexaphosphate in aqueous solution; potentiometric and multinuclear magnetic resonance studies

Potentiometric methods and multinuclear NMR spectroscopy have been used to determine the protonation sequence and conformational preferences of myo-inositol (cyclohexane-1,2,3,4,5,6-hexol) hexaphosphate over the range pH 0–12. The 1H, 31P and 13C resonances have been assigned from both homo- and hetero-nuclear coupling constants obtained by one- and two-dimensional NMR spectroscopy. The phosphate exists in aqueous solution in either of two conformations, axial and equatorial, as a result of intramolecular hydrogen-bond formation between phosphate groups which leads to stabilization of the equatorial form up to pH 10 and of the axial at pH > 10. Analysis of lanthanide-induced shift data shows unambiguously that the last protonation occurs on the P2 phosphate group in strongly acidic media.

Triperchloratoytterbium(III) monohydrate, Yb(ClO4)3.H2O

The crystal structure of triperchloratoytterbium(III) monohydrate, Yb(ClO 4 ) 3 .H 2 O, has been determined. In this coordination compound, bidentate and tridentate perchlorato groups form a channelled three-dimensional network. The eightfold coordination of ytterbium is completed by one strongly bound water molecule lying inside the channels.

Crystal and molecular structure of anhydrous copper(II) perchlorate

The structure of the pale blue-green Cu(ClO4)2 obtained by sublimation has been determined from single-crystal X-ray diffraction data. The structure was refined in the monoclinic space group P21/c, Z= 2, a= 4.584(1), b= 8.326(2), c= 8.015(1)A and β= 114.21(1)°R= 0.044 for 894 observed reflections. The copper has a distorted-octahedral environment with four equatorial oxygen atoms at short distances [1.96(1)A] and two long Cu–O axial interactions [2.46(1)A]. Perchlorate groups are bridging bidentate, and can be regarded as pseudo-tridentate, leading to a three-dimensional polymeric network of infinite cross-linked chains interacting through long Cu–O contacts.

Synthesis and structural analysis of a homogeneous series of anhydrous rare-earth-metal perchlorates

The reaction of Cl2O6 with anhydrous or hydrated metal(III) chlorides, nitrates or hydrated perchlorates leads to anhydrous metal perchlorates M(ClO4)3(M = Y, La, Nd, Sm, Gd or Er). The complexes are isostructural and crystallise in the monoclinic system (space group P21/m): 8.219(6) < a < 8.384(6), 5.602(1) < b < 5.869(9), 7.329(4) < c < 7.481(2)A, 102.88(4) < β < 104.09(5)°, 328.957 < U < 357.110 A3. Vibrational spectroscopic data show a bridging tridentate co-ordination of ClO4, and a polymeric layered structure, derived from that of UCl3, is suggested. Intense fluorescence of Er3+ in the Er(ClO4)3 complex has been observed. The synthesis and characterisation of three salts, (NO2)3Er(ClO4)6, ClO2Er(ClO4)4 and (ClO2)0.33La(ClO4)3.33, are also described.

A New Pentachlorotellurate(IV): catena-Poly[hexakis(acetonitrile)aluminium tris[tetrachlorotellurate(IV)-μ-chloro] acetonitrile]

In the title compound, [Al(CH 3 CN) 6 ][TeCl 5 ] 3 .CH 3 CN, the polymeric anions form infinite helical chains from apex-sharing distorted octahedral TeCl 6 units. These anionic chains are stabilized by [Al(CH 3 CN) 6 ] 3+ counterions.