STEREOCHEMISTRY OF HEXAOXO-MU-ETHYLENEDIAMINETETRAACETATO-DIMOLYBDATE(6) ION IN CRYSTALLINE SODIUM SALT AND IN AQUEOUS SOLUTION

A quantitative stereochemical description of the binuclear anion consisting of two molybdenum trioxide moieties that are bridged and stabilized through a complexing ethylenediaminetetraacetate ion (A4-) emerges from the determination by X-ray analysis of the atomic arrangement in the crystalline sodium salt, Na4(O3MoAMoO3)·-8H2O. The MoO3 moiety in the octahedral coordination group of each Mo(VI) atom exhibits full double bonding with angles approaching the regular tetrahedral values, whereas the complexing links to nitrogen and carboxylate oxygen atoms carry, at most, bond orders of unity. The O3MoAMoO34- complex, required in the crystal to possess a center of inversion, departs rather little from the higher symmetry of C2h-2/m. The unit cell of the monoclinic crystals containing 2Na4(O3MoAMoO3)·8H2O has a = 8.50, b = 11.56, c = 13.36 Å, and β = 87.25; calculated and measured densities are 2.057 and 2.05 g/cc, respectively. The space group is P21/c. Some 3857 independent nonvanishing reflections, approximately 1.3 times the number comprised within the Cu Kα limiting sphere, were photographically recorded with Mo Ka radiation; intensities were visually estimated. Structure determination utilized Patterson and Fourier methods followed by anisotropic full-matrix least-squares refinement; a conventional R of 0.090 was obtained. © 1969, American Chemical Society. All rights reserved.