Crystals and X-Ray

The stmcture of Pmssian Blue and its analogues consists of a three-dimensional polymeric network of Fe —CN—Fe linkages. Single-crystal x-ray and neutron diffraction studies of insoluble Pmssian Blue estabUsh that the stmcture is based on a rock salt-like face-centered cubic (fee) arrangement with Fe centers occupying one type of site and [Fe(CN)3] units randomly occupying three-quarters of the complementary sites (5). The cyanides bridge the two types of sites. The vacant [Fe(CN)3] sites are occupied by some of the water molecules. Other waters are zeoHtic, ie, interstitial, and occupy the centers of octants of the unit cell. The stmcture contains three different iron coordination environments, Fe C, Fe N, and Fe N4(H20), in a 3 1 3 ratio. 

G.M. Brown, M.-R. Noe-Sprilet, W.R. Busing, and H.A. Levy, Dodecatungstophosphoric Acid Hexahydrate, (HsC MPWuCLo3 ). The True Structure of Keggin s Pentahydrate from Single-Crystal X-ray and Neutron Diffraction Data, Acta Cryst., B33, 1038-1046 (1977). 

In the next four subsections, we shall describe the results of statistical surveys of single crystal X-ray and protein crystallographic data bases of atomic coordinates. These surveys document the existence of statistically significant preferences of certain three-dimensional geometric arrange-... 

Treatment of the alkyls with an equimolar amount of PhSiFi3 in hexane led to formation of the first known dimeric lanthanide hydrides in a bis(guanidinato) coordination environment (Scheme 25) [6,7,33,34]. These represent a new family of Lewis base free hydrido complexes of the rare earth elements. Single-crystal X-ray and solution NMR studies revealed that these complexes are dimeric in both the... 

Brown, G.M. Noe-Spirlet, M.-R. Busing, W.R. Levy, H.A. Dodecatungstophosphoric acid hexa-hydrate, (H5O2 )3(PWi2O40 ). The true structure of Keggin s pentahydrate from single-crystal X-ray and neutron diffraction data. Acta Cryst. 1977, B33, 1038. 

Various techniques are available for the investigation of the solid state. These include microscopy (including hot-stage microscopy, HSM), infrared spectrophotometry (IRS), single-crystal X-ray and X-ray powder diffraction (XRPD), thermal analysis, and dilatometry. 

Comparison of results obtained by Single Crystal X-ray and powder diffraction studies... 

Sherwood D (1976) Crystals, X-Rays and Proteins, London, Longman... 

Brigatti MF, Lalonde AE, Medici L (1999) Crystal chemistry of Fe -rich phlogopites a combined single-crystal X-ray and Mossbauer study. 11th Int l Clay Conf, Ottawa, 1977, p 317-327... 

Stucki JW, Roth CB, Baitinger WE (1976) Analysis of iron-bearing clay minerals by electron spectroscopy from chemical analysis (ESCA). Clays Clay Minerals 24 289-292 Swope J (1997) Single crystal X-ray and neutron diffraction studies of the crystal chemical effects of OH=0 substitution in mantle ratile and of Cl-OH substitution in biotite, and the crystal chemistry of IM ferromagnesian trioctahedral micas. PhD dissertation, Dept Geological Sciences, University of Colorado, Botrlder, 85 p... 

There has also been considerable interest in the bis(l,l-dialkylethylenediamine) complexes of Cu and Ni as these exhibit marked thermochroism. The origin of this effect still remains to be precisely defined, despite approaches using ESR, single-crystal X-ray and high-pressure techniques. 

Structural details concerning coordination polyhedra are still best elucidated by single crystal X-ray and neutron diffraction studies, although it is clear that the newer techniques of NMR and ESR have apphcation. The structural variety displayed by the complexes between the actinide fluorides and the alkah fluorides has been amply demonstrated in the foregoing sections. Even with their different structures, such complexes display common characteristics which are independent of such packing details. Prominent among such general properties axe unit cell volume and refractivity volume, both of which are additive functions of composition. 

Morris, R.H. Sawyer. J.F. Single crystal x-ray and neutron diffraction studies of an r -dihydrogen transition-metal 28. complex Trans-[Fe(ri -H2)(H)(PPh2CH2CH2 PPh2)2]BPh4. 

Sherwood. D. Crystals, X-rays and Proteins Longman London, 1976. 

Nuclear magnetic resonance (NMR)—Unlike other structural techniques, such as powder and single-crystal x-ray and neutron diffraction, which characterize the "long-range" order, giving an average view of a structure, solid-state NMR probes the local environment of a particular nucleus and, therefore, is highly suited to study amorphous or disordered materials, such as modified LDH. An extensive review of NMR studies related to both the structure and dynamics in LDH materials was reported by Rocha [11]. Herein, we concentrate on site-specific information available from the H and Al solid-state NMR. 

The so-called spinels . Patrie et al. (1964) first described R2MnS4 spinels and R2peS4 spinels (R = Yb, Lu and Sc). Riedel et al. (1977) published a study of polycrystalline spinel Fei+,Yb2 xS4, with 0.4. From MossbaCier spectra it appears that xFe is trivalent. From X-ray powder studies, the tetrahedral site is occupied by iron only, and the octahedral site by a mixture of Fe and Yb. Recently, Tomas et al. (1978) found from single-crystal X-ray and Mossbauer studies, that the tetrahedral site is not fully filled by Fe atoms, and that Yb atoms and some of the Fe atoms occupy 2 series of octahedral sites. The occupancy factors are tetrahedral site 8a 0.8 Fe, normal octahedral site 16d 0.8 Yb-1-0.09 Fe, octahedral site 16c 0.13 Yb-l-0.01 Fe. 

Among the techniques more frequently used for elucidating cluster structures are crystallographic studies by both single-crystal X-ray and neutron-diffraction techniques, multinuclear high resolution nuclear magnetic resonance (NMR), and infrared spectroscopy. 

Single-crystal X-ray and neutron diffraction studies on metal carbonyls and their derivatives are summarized in the last chapter of this Report. Here we mention some results of special interest. 

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