Crystal and molecular structure of a new hexamolybdate-cyclophosphazene complex

Allcock, Harry R.; Bissell, E. C.; Shawl, E. T.

doi:10.1021/ic50130a045

Cited by 133 publications

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“…[Mo VI 6 O 19 ] 2-has λ max at 325 nm, 31 suggesting that the smaller particles have a higher Mo VI /Mo V ratio than the larger particles. Figure 1d shows the variation of Mo content per unit particle volume distribution vs particle size.…”

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Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

et al. 2005

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Reduction reactions of molybdate in acidic, aqueous solution lead to colored, mixed-valent Mo V/VI polyoxomolybdate (POM) species. [1][2][3][4][5] The two-century-old mystery of the "molybdenum blues" 6 exemplifies the difficulty in characterizing suspensions of POM particles. Müller, Liu, and co-workers revealed the fundamental compositions of the related "molybdenum browns", including I h symmetrical keplerates. In general, reduced molybdates assemble into nanometric species (Figure 1a). Light-scattering, small-angle X-ray scattering (SAXS), and microscopy show slow aggregation of Na 15 The key methodology of our study is field-flow fractionation (FFF), a flow-based, chromatography-like separation and sizing technique that can monitor changes in the particle-size distribution of a suspension in situ. FFF is conducted in a thin, empty channel, with separation based on relative hydrodynamic behavior. [21][22][23] In flow field-flow fractionation (FlFFF), a cross-flow perpendicular to the direction of laminar channel flow forces dissimilar particles to different levels in the channel, where they are eluted at different flow velocities. FlFFF fractionates particles between 1 and 1000 nm and allows analysis of the eluate. 24 We used FlFFF to monitor the evolution of molybdate nanoparticles in a {Mo 132 } suspension prepared by Müller's procedure. 7,15,16 Under our FlFFF conditions, 25 soluble species and particles smaller than 3 nm are swept to the waste stream by the cross-flow, while larger particles are separated and eluted through a UV-visible detector. FlFFF fractograms monitoring the absorbance of the eluate at 455 nm are shown in Figure 1b.The particle-size distributions calculated 26 from the data in Figure 1b have diameters ranging from 3 to 75 nm, roughly distributed in three populations with maxima about 3.4, 12, and 25 nm. The mean diameter is 31((1) nm (confidence level 95%), averaged over 24 FFF runs from 8 days. The baseline fractogram at 10 min indicates that no particles over ca. 3 nm had yet formed. At 2 h, the 3.4-nm population is largest. The total area under the fractogram increases rapidly from 2 to 8 h, at which time the 12-and 25-nm populations are larger. We suggest that the 3.4-nm particles, decreasing after 2 h but observed consistently throughout the entire period, are the {Mo 132 } with their associated counterions and solvation shell. The overall particle population reaches a maximum at ca. 8 h, decreases rapidly for about 2 days and more slowly thereafter (Figure 1b). The decrease parallels the precipitation of large particles that are not sampled by FlFFF shown in the SEM 27 image in Figure 2a. The precipitate is in dynamic equilibrium with species still in solution or suspension, yielding after several days ca. 0.1-mm octahedral crystals of {Mo 132 }, Fm3 with a ≈ 46 Å, 15 shown in Figure 2b.The particle-size distribution of the molybdate suspension was corroborated by AFM, SEM, and HRTEM. Good agreement between particle-size distributions obtained by FFF and microscopy suggests t...

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Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

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“…ref. 9), but, in contrast to the marked alternation in bond lengths found in the structures of protonated phosphazenes (10)(11)(12)(13)(14), the P-N bonds vary only slightly in length. The averages of the P( …”

Section: Resultsmentioning

confidence: 75%

Crystal and molecular structure of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(P^v)-triphosphorin

Oakley¹,

Paddock²,

Rettig³

et al. 1977

Can. J. Chem.

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Crystals of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(Pv)-tri-phosphorin are triclinic, a = 13.375(1), b = 11.313(1), c = 7.925(1) Å, α = 107.72(1), β = 98.23(1), γ = 87.00(1)°, Z = 2, space group [Formula: see text]. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to a final R of 0.067 and Rw of 0.089 for 3954 reflections with. I ≥ 3σ(I) The P3N2C ring is nearly planar and has a conformation corresponding to a flattened version of the chair – twist boat. Bond lengths in the azaphosphorin ring, P—N, 1.579–1.614(2), and P—C, 1.752(3) and 1.777(3) Å, indicate conjugation with the C-benzoyl group. The exocyclic P—N bond length, 1.742(3) Å, is longer than those in related compounds as a result of competitive electron withdrawal from the N-benzoyl group. Other bond lengths (corrected for libration) are: mean P—Me, 1.796(4); C=O, 1.242(3) and 1.247(4); C—N, 1.472(3) and 1.369(4); mean C—C(phenyl), 1.391(10); other C(sp2)—C(sp2); 1.417–1.518(4) Å.

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“…Von den aus angesS.uerten wfissrigen L6sungen kristallisierenden Alkaliisopolymolybdaten sind bisher die Strukturen der Heptamolybdate M6MOTOz4.4H20 (M=NH+,K+,Rb+,Na +) (Lindqvist, 1950b,c;Shimao, 1967;Evans, 1968;Gatehouse & Leverett, 1968;Sj6bom & Hedmann, 1973;Evans, Gatehouse & Leverett, 1975), des Oktamolybdat-Ions im (NH4)4MosO26.4HzO und (NH4)4MosOa6 • 5H20 (Lindqvist, 1950d;Atovmyan & Krasochka, 1972), des Polyoktamolybdats (NH4)6MosOzT.4H20 (B6schen, Buss, Krebs & Glemser, 1973;B6schen, Buss & Krebs, 1974), des Hexamolybdats [HN3P3(NMe2)6]2Mo6Oa9 (Allcock, Bissell & Shawl, 1973) und des sogenannten Dimolybdats (NH4)2Mo207 (Kn6pnadel, Hartl, Hunnius & Fuchs, 1974) bekannt. Das erste echte strukturell charakterisierte Dekamolybdat mit isolierten MoloO~4-Ionen ist das kilrzlich beschriebene (NH4)sMo10034 (Fuchs, Hartl, Hunnius & Mahjour, 1975).…”

Section: Introductionunclassified

“…Fig. 2 (Lindqvist, 1950b,c;Shimao, 1967;Evans, 1968;Gatehouse & Leverett, 1968;Sj6bom & Hedmann, 1973;Evans, Gatehouse & Leverett, 1975), des Hexamolybdat-Ions MO6029 (Allcock, Bissell & Shawl, 1973), des Oktamolybdat-Ions MosO46 (Lindqvist, 1950d;Atovmyan & Krasochka, 1972), des PolyoktamolybdatIons (Mo8067),, (B6schen, Buss, Krebs & Glemser, 1973;B6schen, Buss & Krebs, 1974;B6schen, 1974) und des echten Dekamolybdat-Ions Mo10084 (Fuchs, Hartl, Hunnius & Mahjour, 1975) (Sotani, 1975), eine gewisse Berechtigung. Die 'Dekamolybdate' weisen keine isolierten Polyanionen mehr auf, sondern bilden /~hnlich den bei weiterem AnsS.uern der L6sungen auskristallisierenden Oxidhydraten polymere Strukturen.…”

Section: Introductionunclassified

Kristallstruktur des sogenannten Kaliumdekamolybdats KMo₅O₁₅OH.2H₂O

Krebs¹,

Paulat‐Böschen²

1976

Acta Crystallogr Sect B

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The crystal structure of the so-called potassium decamolybdate, the formula of which has to be written as KMosOlsOH. 2H20, was determined from single-crystal diffractometer data. The compound crystallizes with hexagonal symmetry in the space group P63/m, the cell parameters being a= 10.550 (8), c--3-727 (3) ,~ and Z= 1. The structure has been solved from the Patterson function and chemical considerations and refined by full-matrix least squares to a conventional R of 0.042 based on 335 independent reflexions. The structure consists of double chains made of edge-sharing, strongly distorted MoO6 octahedra. The double chains are linked by common corners of octahedra to form a threedimensional network. The double chains are not perfect due to statistical non-occupation of one of the six equivalent Mo positions in the unit cell. Along the short c axis the polymeric structure forms tunnels in which the potassium ions are located. Mo-O bond lengths in the MoO6 octahedra are: 1.698, 1.701, 1.955 (2 x ), 2.190 and 2.373/~. The chemical composition and the observed interatomic distances lead to a plausible model of the structural disorder: In the neighbourhood of a vacant Mo position the O atoms are partially replaced by coordinated H20 molecules, isolated H20 molecules (crystal water), and OH groups. The statistical distribution of the Mo vacancies can be interpreted as resulting in smaller sub-units of edge-sharing octahedra linked in the direction of the double chains only by common corners. The structure is only weakly related to the structures of the other typical polymolybdates crystallizing from aqueous solutions. Closer relations are found to the structures of ~-MoO3.H20 and of MOO3.

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Crystal and molecular structure of a new hexamolybdate-cyclophosphazene complex

Cited by 133 publications

References 4 publications

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Crystal and molecular structure of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(P^v)-triphosphorin

Kristallstruktur des sogenannten Kaliumdekamolybdats KMo₅O₁₅OH.2H₂O

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Crystal and molecular structure of a new hexamolybdate-cyclophosphazene complex

Cited by 133 publications

References 4 publications

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Monitoring the Growth of Polyoxomolybdate Nanoparticles in Suspension by Flow Field-Flow Fractionation

Crystal and molecular structure of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(Pv)-triphosphorin

Kristallstruktur des sogenannten Kaliumdekamolybdats KMo5O15OH.2H2O

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Crystal and molecular structure of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(P^v)-triphosphorin

Kristallstruktur des sogenannten Kaliumdekamolybdats KMo₅O₁₅OH.2H₂O