Crystal and anion structure, TGA, DTA, and infrared and Raman spectra of managanese(II) nitroprusside dihydrate, Mn [Fe(CN)5NO]·2H2O

Abstract

The single crystal and anion structure of Mn[Fe(CN)sNO'2H~_O, obtained by slow interdiffusion of reactant solutions through a TMS gel, was solved by X-ray diffraction methods and refined to RI = 0.036. Spatial group: orthorhombic, Prima, a = 14.069(2), b = 7.538(1), c = 10.543(1),~,, Z = 4. The Mn(ll) ion and the water molecules are sited on mirror planes, which bisect the nitroprusside ions. One of the water molecules is coordinated to Mn(lI) and the other, strongly hydrogen (as acceptor) bonded to the first molecule. The IR spectrum confirms the bonding of the water molecules and TGA results are in accordance with the dihydrate character of the substance and its dehydration in two successive steps. DTA results and the Raman spectrum agree with other results and the comparison between IR and Raman vNO wavenumbers confirms the expected strong vibrational interaction between the closely packed antiparallel (eclipsed) NO groups. There is a topotactic relationship between the dihydrate and the trihydrate, which crystallizes in the space subgroup P2Jn.

Crystal structure of orthorhombic ferrous nitroprusside: Fe[Fe(CN)5NO].2H2O

“…The trihydrate and the dihydrate iron complexes are practically isomorphous, a fact also observed in the corresponding Mn and Cd nitroprussides (Benavente et al , 1997; Gomez et al , 2001). If, in the trihydrate structure, the weakest hydrogen bonded water molecule is omitted, the remaining atoms are located within a deviation of 0.2 Å from their ideal positions corresponding to the space group P n m a .…”

“…The structural refinement from the XRD powder pattern was performed with the program FULLPROF (Rodriguez-Carvajal, 1998) using pseudo-Voigt peak shape functions. As starting structural models to be refined, the reported structure for manganese nitroprusside (Benavente et al , 1997) was used. Peak profiles were calculated within ten times the full width at half maximum (FWHM) and corrected for asymmetry below 30° (2 θ ) (Berar and Lelann, 1991).…”

“…Since the monoclinic single crystals usually break during the drying process (Gomez et al , 2001), the structural refinement was carried out using the Rietveld method. The reported structure for the manganese analog (Benavente et al , 1997) was used as the structural model to be refined. The X-ray powder diffraction (XRD) data were complemented with information from themogravimetric analysis (TGA) and Mössbauer and IR spectroscopies.…”

Crystal structures of cubic nitroprussides: M[Fe(CN)5NO]·xH2O(M=Fe, Co, Ni). Obtaining structural information from the background

“…The improvement in the pattern fitting and refinement reliability in the second option were significant (Figure 1 and Table I). Considering that in nitroprussides the complex anion behaves as a practically rigid block with a weak dependence on the outer metal, as their IR and Mössbauer spectra suggest (Balmaseda et al , 2003), in the first stage of the refinement process the interatomic distances within the nitroprusside anion were constrained to change within the expected values for divalent transition metal nitroprussides (Mullica et al , 1989, 1990, 1991a, b, 1992, 1993; Benavante et al 1997): Fe-C1.936(7)Å,C≡N1.144(6)Å, Fe-N1.669(6)Å, and N=O1.131(6)Å. Removal of these constraints resulted in less satisfactory bond distances and angles without any improvement in the profile fitting.…”

“…These properties suggest the convenience of a proper description of their crystal structure. Fortunately it has been carried out for practically all the divalent transition metals (Mullica et al , 1989, 1990, 1991a, b, 1992, 1993; Benavante et al , 1997; Gómez et al , 2001, 2004; Reguera et al , 1996; Rodríguez-Hernández et al , 2005), except for the cubic phases of Fe(2+) and Ni(2+). For Co(2+) the reported structure (Mullica et al , 1991b) must be reconsidered.…”