M. Ishaque Khan

Hydrothermal synthesis and crystal structure of the trimolybdate, (H3NCH2CH2NH3) Mo3O10

Abstract The hydrothermal reaction of Na2MoO4·2H2O, MoO3, H2NCH2CH2NH2·2HCl and H2O in the mole ratio 6:6:10:300 at 160 °C under autogenous pressure yields colorless needles of (H3NCH2CH2NH3)Mo3O10 (1). The structure of 1 consists of distorted {MoO6} octahedra linked through face-, edge- and corner-sharing interactions into infinite chains. The ethylenediamminium cations occupy the channels between these chains. Crystal data: monoclinic space group P21/n, a=8.083(2), b=14.465(2), c=8.919(2) A, β=98.19(1)°, V=1032.2(7) A3, Z=4, Dcalc=3.28 g cm−3; structure solution and refinement based on 2856 reflections converged at R=0.0191.

Hydrothermal syntheses and structures of reduced and mixed valence polyoxovanadium clusters with capped cage cores: K3[H12(AsO)2(AsO4)V6IVV6VO36]·12H2O and Rb5 [(As2O)4(VO)2V12IVO36Cl]·2H2O

The reaction of NaVO3, As2O3, KSCN, H2NC(CH2OH)3, H2SO4 and H2O yielded black crystals of K3[H12(AsO)2(AsO4)V12O36]·12H2O (1). The structure of 1 consists of a {(AsO4)V12O36} α-Keggin core capped on two tetragonal faces by {AsO} units. Crystal data for H36O54K3V12As3: cubic space group Pm3m, a=10.583(2) A, V=1185.3(9) A3, Z=1, Dcalc=2.664 g cm−3. Structure solution and refinement based on 193 reflections with Io⩾3σ(Io) converged at a discrepancy value of 0.0628. The hydrothermal reaction of a mixture of V2O5, V2O3, V (−325 mesh), H5As3O10, RbOH and H2O in the mole ratio 5:5:5:3:6.4:333 for 60 h at 200 °C produced lustrous black crystals of Rb5[As8V14O42Cl]·2H2O (2). The structure of 2 is similar to those of the general class of ‘reduced’ or V(IV) clusters of the type [V(18−p)As2pO42(X)]m−, where X=SO3, SO4, H2O and p=3, 4, which are topologically related to the elongated square gyrobicupola and extended cage core of [V18O42(X)]n−. Thus, the structure of 2 is constructed from the framework of 24 bridging oxo groups by the capping of four tetragonal faces by {As2O} groups and of fourteen faces by {VO} groups and by encapsulation of a Cl−anion. Crystal data for As8ClH4O44Rb5V14: monoclinic P21, a=13.141(2), b=13.525(2), c=13.412(2) A, β=92.59(1)°, V=2381.3(12) A3, Z=2, Dcalc=3.46 g cm−3. Structure solution and refinement based on 4518 reflections with Io ⩾3σ(Io) converged at R=0.0623.

Protonation sites in a heteropolyvanadate of phosphorus: X-ray crystal structure of (Me3NH)4(NH4)[H4PV14O42]

Abstract The reaction of (NH4)2HPO4 with (NH4)2Na2K2V10O28, followed by addition of Me3NHCl, yields dark crystals of the phosphovanadate cluster (Me3NH)4(NH4)[H4PV14O42]. The structure consists of an α-Keggin framework capped by two [VO] subunits. The protonation sites were identified as the doubly-bridging oxygens, O10. Crystal data: orthorhombic space group Fddd, a=10.706(2), b=23.581(4), c=37.271(8) A, V=9409.3(22) A3, Z=8. X-ray data were collected on a Siemens R3m/V diffractometer using a θ/2θ scan technique with graphite monochromated MoKα radiation. A total of 2733 reflections was collected (to 2θ=55°), of which 1850 were used in subsequent structure solution and refinement (I>3σ(I)). The structure was solved by direct methods, and least-squares refinement converged at R=0.033.

Oxomolybdenum(V) polyanion clusters. Hydrothermal syntheses and structures of (NH4)5Na4{Na[Mo6O12(OH)3(O3PC6H5)4)]2}·6H2O (C6H5CH2NMe3)4K4{K2[Mo6O12(OH)3(O3PC6H5)4]2}·10H2O and their relationship to the binuclear (Et4N)[Mo2O4Cl3(H2O)3]·5H2O

Abstract The hydrothermal syntheses of the binuclear Mo(V) species (Et4N)[Mo2O4Cl3(H2O)3]·0.5H2O (3·0.5H2O) and of the hexanuclear (NH4)5Na4{Na[Mo6O12(OH)3(O3PC6H5)4)]2}·6H2O (1·6H2O) and (C6H5CH2NMe3)4K4{K2[Mo6O12(OH)3(O3PC6H5)4]2}·10H2O (2·10H2O) are described. X-ray crystallography revealed that both 1·6H2O and 1·10H2O contain the cyclic Mo(V) anion [Mo6O12(OH)3(O3PC6H5)4]5− as the fundamental structural motif. This hexanuclear core may be considered as a trimer constructed from {Mo2O10} units consisting of edge-sharing octahedra with alternating short-long Mo(V)Mo(V) distances. The structure of 3·0.5H2O provides a structural prototype for this binuclear unit. Crystal data: 1·6H2O, C48H78N5O60Na5P8Mo12, monoclinic C2/c, a = 31.254(7), b = 30.441(6), c = 13.455(3) A , β = 112.87(2)°, V = 11 795(2) A 3 , Z = 4, Dcalc = 1.80 g cm−3, 2162 reflections, R = 0.069; 2·10H2O, C88H130N4O64P8K6Mo12, monoclinic P2/c, a = 19.203(4), b = 17.221(4), c = 20.949(5) A , b = 98.91(3)°, V = 6844(1) A 3 , Z = 2, Dcalc = 1.86 g cm−3, 4181 reflections, R = 0.065; 3·0.5H2O, C8H27NO7.5Cl3Mo2, monoclinic P21/n, a = 7.923(2), b = 12.255(3), c = 20.511(3) A , β = 100.83(2)°, V = 1956.2(6) A 3 , Z = 4 , Dcalc = 1.89 g cm−3, 2161 reflections, R = 0.060.

A mixed valence heteropolyvanadate, K7Na[AsV4VV7VIV5O43H3]·7H2O

Abstract The reaction of NaVO3 with As2O3, Na2C6O6 and KSCN in water at pH 4.4 yields shiny black crystals of K7Na[AsV4VV7VIV5O43H3]·7H2O. The structure consists of an ϵ-Keggin core {AsV12O40} with three [VO] vertices removed and capped by three [VO] and three [AsOH] units. Crystal data: monoclinic C2/c, a = 40.048(9), b = 13.326(1), c = 18.074(3) A, β = 112.28(1)°, V = 9005.9(14) A3, Dcalc = 2.986 g cm−3, Z = 8, R = 0.063 for 5999 reflections.

Hydrothermal synthesis and crystal and molecular structure of a reduced, arsenic rich heteropolyanion, Na4[Mo4As6O20(OH)2]·9H2O

The hydrothermal reaction of Na3MoO4·2H2O, Mo metal, MnO3, H5As3O10, NaCl and H2O in the mole ratio 6 : 6 : 6 : 3 : 10 : 166 for 110 h at 180 °C yielded orange crystals of the sodium salt of the arsenic-rich MoV–AsIII polyanion cluster, Na4[Mo4As6O20(OH)2]·9H2O.

Synthesis and crystal and molecular structure of (NH4) 4[V10O16{EtC(CH2O)3} 4]·4H2O, a decavanadyl cluster

The hydrothermal reaction of (NH4)VO3 with EtC(CH2OH)3 yields the oxoalkoxovanadium(IV) cluster, (NH4)4[V10O16{EtC(CH2O)3}4]·4H2O, an unusual polyoxoanion coordination complex with a reduced {V10O28} core.

Coordination chemistry of the tetrametalate core, {M4O16}: syntheses from [V2O2Cl2{(OCH2)2C(R)(CH2OH)}2] and structures of the mixed-metal cluster [V2Mo2O8(OMe)2{(OCH2)3CR}2]2– and the reduced cluster [V4O4(H2O)2(SO4)2{(OCH2)3CR}2]2–

The reactions of [Ph3PCH2Ph][VO2Cl2] with (HOCH2)3CR yield binuclear species of the type [V2O2Cl2{(OCH2)2C(R)(CH2OH)}2], which react in turn with [Bun4N]2[Mo2O7] to give the mixed-metal tetrametalates, [V2Mo2O8(OMe)2{(OCH2)3CR}2]2– and with [Bun4N]HSC4 and [Bun4N]3[H3V10O28] to yield the reduced tetravanadium clusters [V4O4(H2O)2(SO4)2{(OCH2)3CR}2]2–.