Multicomponent Polyanions. 53. Structure of Tetrakis(trimethylammonium) Tetra-μ-oxo-bis(triaquahexadecaoxo(trioxophenylphosphato)hexamolybdate) Dihydrate, [NH(CH₃)₃]₄[{(C₆H₅P)Mo₆O₂₁(H₂O)₃}₂].2H₂O

Abstract

The title compound crystallized in the monoclinic space group P2 1 /n (No. 14) [a = 11.211 (5), b = 12.862 (3), c = 23.05 (1) A Ê , = 94.37 (3), V = 3314 (2) A Ê 3 , Z = 2]. The polyanion can be regarded as a dimer of a phenylphosphonatohexamolybdate, (C 6 H 5 P)Mo 6 O 23 (H 2 O) 3 , linked by four O atoms. In this monomeric unit the six molybdenum octahedra are grouped into two parts consisting of four and two edge-sharing octahedra, respectively. These two parts are connected by two corner-sharing O atoms to form a bent Mo 6 ring. The phenylphosphonate group coordinates to the Mo 6 ring from the narrow side as a tripodal ligand. The {(C 6 H 5 P)Mo 6 O 21 (H 2 O) 3 } 2 units form layers parallel to (001) and the structure is stabilized by hydrogen bonds between water and neighboring anions. The monomeric unit has been shown to be a key structure in the process of deducing the aqueous solution structures of the (C 6 H 5 P)Mo

Multicomponent Polyanions. 57. Large-Angle X-ray Scattering Study of Aqueous Molybdophenylphosphonate Solutions

“…The main purpose of the present study was to determine the aqueous structures of the complexes formed in the system and to understand why two of the species with different nuclearities are in rapid exchange on the 31 P NMR time scale. The close correlation between the observed and calculated s · i(s) functions confirms that the structure of the discrete anion (C 6 H 5 P) 2 Mo 5 O 21 4- (Mo 5 (PhP) 2 ) and that of the monomic unit Mo 6 PhP, discernible in the dimeric [(C 6 H 5 PO 3 )Mo 6 O 18 (H 2 O) 3 ] 2 4- anion, both found in single-crystal X-ray determinations, , are present in aqueous solution. Modeling of the Mo 7 PhP complex, based on the (C 6 H 5 AsO 3 ) 2 Mo 6 O 18 (H 2 O) 4- structure, also confirms the relevance of the earlier proposed structure, and it was even possible to localize the water oxygen site in the structure due to the lengthening of the Mo 2 ···Mo distances.…”

“…Recently, a single-crystal X-ray investigation was reported for a trimethylammonium salt containing the [(C 6 H 5 PO 3 )Mo 6 O 18 (H 2 O) 3 ] 2 4- anion (Figure h), which consists of two (C 6 H 5 PO 3 )Mo 6 O 18 (H 2 O) 3 entities weakly bound to each other. This anion can be regarded as a dimer of these entities according to the equilibrium The (C 6 H 5 PO 3 )Mo 6 O 18 (H 2 O) 5 2- complex (model B, Figure i) has a bent six-membered ring of MoO 6 octahedra similar to the complex shown in Figure f (model A) except that the group of two MoO 6 octahedra (Mo2 group) is edge-shared instead of face-shared.…”

An equilibrium analysis of the aqueous H+–MoO42−–(HP)O32−and H+–MoO42−–(HP)O32−–HPO42−systems

“…A crystal structure of a related phenylphosphonate compound, [NH(CH 3 ) 3 ] 4 [{(C 6 H 5 P)-Mo 6 O 21 (OH 2 ) 3 } 2 ]•2H 2 O, has been determined. 17 The polyanion [{(C 6 H 5 P)Mo 6 O 21 (OH 2 ) 3 } 2 ] 4− can be regarded as a dimer of [(C 6 H 5 P)Mo 6 O 23 (OH 2 ) 3 ] 6− having a 'bent' structure. It may be tetraprotonated at low ph, and probably corresponds to the H 12 Mo 6 (C 6 H 5 P) 2− ((C 6 H 5 P) denotes phenylphosphonate) species found in the phenylphosphonatomolybdate system.…”

Phosphoesterase activity of polyoxomolybdates: diffusion ordered NMR spectroscopy as a tool for obtaining insights into the reactivity of polyoxometalate clusters

“…11 Previous studies of molybdophenylphosphonate solutions suggested that besides the major pentamolybdodiphosphate 4À complex, which consists of two weakly binding (PhP)Mo 6 O 18 (H 2 O) 3 entities has been isolated and characterized by X-ray crystallography. 12 Although it has been proposed that this complex forms in strongly acidic solutions 10b,12 it is possible that slight changes in ligand structure may cause its formation also in mildly acidic media.…”