Change In Coordination Number Research Articles

Experimental and theoretical investigations on the structure-properties interrelationship of the gadolinium-vanadate-germanate glasses

Glasses in the system xGd₂O₃·(100-x)[GeO₂·V₂O₅] with 0 ≤ x ≤ 20 mol% have been prepared from the melt quenching method. In this paper, we investigated changes in germanium coordination number in gadolinium-vanadate-germanate glasses through molar volume analysis, measurements of densities, investigations of FTIR and UV-VIS spectroscopy, calculations of density functional theory (DFT). Analyzing the structural changes resulted from the IR spectra we found that the gadolinium ions have a pronounced affinity toward [VO₄] structural units which contain non-bridging oxygens necessary for the charge compensation. The introduction of the excess of oxygen yields the formation of [VO₅] structural units. This attains maximum value at 5 mol% Gd₂O₃, in agreement with the density measurements. Further, the addition of the surplus of oxygen implies the transformation of [VO₅] to [VO₄] structural units and the formation of VO₄⁻³ orthovanadate structural units. The UV-VIS spectra show a broad UV absorption band located in the 300-500 nm region. These bands are assumed to originate from the combination of vanadium ions possibly present in the three states of valence. The presence of Ge-Ge wrong bonds attains its maximum values in the samples with x = 5 and 15 mol% Gd₂O₃ (bands centered in the 250-300 nm range). DFT calculations show the massive vibrations of the [VO(n)] structural units coupled with each other via [GeO₆] and [GeO₄] structural units. This leads to the splitting of the bridge modes and a multiplication of the number of these bands.

Si═X Multiple Bonding with Four-Coordinate Silicon? Insights into the Nature of the Si═O and Si═S Double Bonds in Stable Silanoic Esters and Related Thioesters: A Combined NMR Spectroscopic and Computational Study

The electronic structures and nature of silicon-chalcogen double bonds Si=X (X = O, S) with four-coordinate silicon in the unique silanoic silylester 2 and silanoic thioester 3 have been investigated for the first time, by (29)Si solid state NMR measurements and detailed DFT and ab initio calculations. (29)Si solid state NMR spectroscopy of the precursor silylene 1 was also carried out. The experimental and computational study of 2 and 3, which was also supported by a detailed computational study of smaller model systems with Si=O and Si=S bonds, provides a deeper understanding of the isotropic and tensor components of their NMR chemical shifts. The general agreement between the experimental NMR spectra and the calculations strongly support our previous NMR assignment deduced from experiment. The calculations revealed that in 2 delta((29)Si(=O))(iso) is shifted upfield relative to H(2)Si=O by as much as 175 ppm; the substituents are responsible for ca. 100 ppm of this shift, while the remaining upfield shift is caused by change in the coordination number from three to four at the Si=O moiety. The change in coordination number leads to a nearly cylindrical symmetry in the plane which is perpendicular to the Si=O molecular axis (delta(11) approximately delta(22)), in contrast to the significant anisotropy found in this plane in typical doubly bonded compounds. The change in r(Si=O) or in the degree of pyramidality at the Si=O center which accompanies the change in coordination number has practically no effect on the chemical shift. delta((29)Si(=S))(iso) in 3 is shifted downfield significantly relative to that in 2, and a similar trend is found in smaller models with Si=S vs those with Si=O subunits. This downfield shift can be explained by the smaller sigma-pi* energy difference in the Si=S bond, relative to that of the Si=O bond. The NMR measurements of 2 and 3 having a four-coordinate silicon-chalcogen moiety, and the calculations of their tensor components, their bond polarities, and their Wiberg bond indices revealed that the Si=X moieties in both 2 and 3 have a significant pi(Si=X) character; yet, in both molecules there is a substantial contribution from a zwitterionic Si(+)-X(-) resonance structure, which is more pronounced in 2.

Synthesis and Spectral Studies on N,N,N′,N′-Tetramethylethylenediamine Adducts of Bis(4-methylpiperidinecarbodithioato-S,S′)M(II) (M = zinc, cadmium): Single Crystal X-Ray Structure of Bis(4-methylpiperidinecarbodithioato-S,S′) (N,N,N′,N′-Tetramethylethylenediamine)zinc(II)

Bis(4-methylpiperidinecarbodithioato-S,S′)(N,N,N′,N′-tetramethylethylenediamine)zinc(II), [Zn(4-mpipdtc)2(TMED)] (1) and bis(4-methylpiperidinecarbodithioato-S,S′)(N,N,N′,N′-tetramethylethylenediamine)cadmium(II), [Cd(4-mpipdtc)2(TMED)] (2) adducts were synthesized and characterized by IR and NMR (1H and 13C) spectra. A single crystal X-ray structural analysis was carried out for complex 1. IR spectra of the complexes show the contribution of the thioureide form to the structures. Reduction in νC–N(thioureide) for the adducts is attributed to the change in coordination number from four to six. In the 13C NMR spectra, the downfield shift of NCS2 carbon signal for 2 (205.20 ppm) from the chemical shift value of 1 (202.05 ppm) in due to large size of cadmium ion in 2 experiences less steric effect involved in transformation from tetrahetral to octahedral. Single crystal X-ray structural analysis of 1 showed that zinc is in a distorted octahedral environment with a ZnS4N2 chromophore. The Zn–S distances in 1 are longer than those in parent [Zn(4-mpipdtc)2]. The acceptance of an additional neutral ligand by the [Zn(4-mpipdtc)2] to form an octahedral adduct causes an increase in the Zn–S bond lengths and a consequent lowering of the S–Zn–S bite angle. The piperidine ring in the dithiocarbamate fragment is in the normal chair conformation. Bis(4-methylpiperidinecarbodithioato-S,S′)(N,N,N′,N′-tetramethylethylene-diamine)zinc(II) (1), and bis(4-methylpiperidinecarbodithioato-S,S′)(N,N,N′,N′-tetramethylethylene- diamine)cadmium(II) (2) were synthesized and characterized by IR and NMR (1H and 13C) spectra and the structure of 1 was determined by single crystal X-ray crystallography.

Spectroscopic Evidence for Ultrahigh-Pressure Polymorphism inSiO2Glass

Acoustic wave velocities of SiO2 glass were measured up to pressures of 207 GPa using newly developed Brillouin scattering spectroscopic techniques to address the nature of pressure-induced structural changes. The acoustic wave velocity data suggests three distinct pressure regimes, two of which correspond to changes in the Si-O coordination number with pressure, and one of which indicates the stability of sixfold-coordinated Si over a broad pressure interval from approximately 40-140 GPa. An anomalous increase in the effect of pressure on velocity at 140 GPa most likely corresponds to the onset of structural densification associated with an increase in coordination number from sixfold to a higher coordination state.

Dissociation of nitric acid at an aqueous surface: Large amplitude motions in the contact ion pair to solvent-separated ion pair conversion

Beyond its fundamental interest, the acid dissociation of nitric acid (HNO(3)) at an aqueous interface is of importance in a wide variety of atmospheric contexts. Here we present a Car-Parrinello molecular dynamics (CPMD) study of the second step of this process, the formation, via proton transfer (PT), of a solvent-separated ion pair (SSIP) from a contact ion pair (CIP) of the hydronium (H(3)O(+)) and the nitrate (NO) ions. This reaction represents an extension of our earlier CPMD study of the first PT step to produce the CIP from molecular HNO(3) at various locations at and below the aqueous surface (S. Wang, R. Bianco and J. T. Hynes, J. Phys. Chem. A, 2009, 113, 1295); it is important in establishing the ionic distribution in the aqueous interfacial region, with potential consequences for heterogeneous reactions occurring in that region. We focus on the large amplitude, microscopic level motions-such as the hydrogen-bonding coordination number changes around the proton-donating and -accepting species-which are key for the CIP --> SSIP PT conversion.

Structural Relaxation around Cr3+ in YAlO3−YCrO3 Perovskites from Electron Absorption Spectra

The structural relaxation around Cr(3+) in YAl(1-x)Cr(x)O(3) perovskites was investigated and compared with analogous Cr-Al joins (corundum, spinel, garnet). Eight compositions (x(Cr)((3+)) from 0 to 1) were prepared by sol-gel combustion and were analyzed by a combined X-ray diffraction (XRD) and electron absorption spectroscopy (EAS) approach. The unit cell parameters and the XRD averaged octahedral (Cr,Al)-O and ([VIII])Y-O bond distances scale linearly with the chromium fraction. The optical parameters show an expected decrease of crystal field strength (10Dq) and an increase of covalency (B(35)) and polarizability (B(55)) toward YCrO(3), but a nonlinear trend outlines some excess 10Dq below x(Cr)((3+)) approximately 0.4. The local Cr-O bond lengths, as calculated from EAS, indicate a compression from 1.98 A (x(Cr)((3+)) = 1.0) down to 1.95 A (x(Cr)((3+)) = 0.035) so that the relaxation coefficient of perovskite (epsilon = 0.54) is the lowest in comparison with garnet (epsilon = 0.74), spinel (epsilon = 0.68), and corundum (epsilon = 0.58) in contrast with its structural features. The enhanced covalent character of the Cr(3+)-O-Cr(3+) bond in the one-dimensional arrangement of corner-sharing octahedra can be invoked as a factor limiting the perovskite polyhedral network flexibility. The increased probability of Cr-O-Cr clusters for x(Cr)((3+)) greater than approximately 0.4 is associated to diverging trends of nonequivalent interoctahedral angles. The relatively low relaxation degree of Y(Al,Cr)O(3) can be also understood by considering an additional contribution to 10Dq because of the electrostatic potential of the rest of the lattice ions upon the localized electrons of the CrO(6) octahedron. Such an "excess" of 10Dq increases when the point symmetry of the Cr site is low, as in perovskite, and would be affected by the change of yttrium effective coordination number observed by XRD for x(Cr)((3+)) greater than approximately 0.4. This would justify the systematic underestimation of local Cr-O bond distances, as inferred from EAS, compared to what is derived from X-ray absorption (XAS) studies implying a stronger degree of relaxation around Cr(3+) of all the structures considered and supporting the hypothesis that 10Dq from EAS contains more information than previously retained particularly an additional contribution from the next nearest neighboring ions.

Mono-, Di-, Tri- and Tetranuclear Rare Earth Complexes Obtained Using a Moderately Bulky Aryloxide Ligand

Redox transmetallation ligand exchange reactions involving a rare earth metal, 2,4,6-trimethylphenol (HOmes), and a diarylmercurial afford rare earth aryloxo complexes, which are structurally characterized. Both the lanthanoid contraction and the identity of the reaction solvent are found to influence the outcome of the reactions. Using THF in the reaction affords a dinuclear species [Ln2(Omes)6(thf)4].2THF (Ln=La 1, Nd 2) for the lighter rare earth metals, while a mononuclear species [Ln(Omes)3(thf)3] (Ln=Sm 3, Tb 5, Er 6, Yb 7, Y 8) is obtained for the heavier rare earth elements. Surprisingly, there is no change in metal coordination number between the two structural motifs. A divalent trinuclear linear complex [Eu3(Omes)6(thf)6] 4 is obtained for Eu, and features solely bridging aryloxide ligands. Using DME as the reaction solvent affords [La(Omes)3(dme)2] 9 from the reaction mixture, and [Ln2(Omes)6(dme)2].PhMe (La 10, Nd 11) and [Y(Omes)3(dme)2] 14 following crystallization of the crude product from toluene. The dinuclear species [Eu2(Omes)4(dme)4] 12 contains two unidentate and two chelating DME ligands, and contrasts the linear structure of 4. Treatment of HOmes and HgPh2 with Yb metal in DME affords the mixed valent Yb(II/III) complex [Yb2(Omes)5(dme)2] 13, which is stabilized by an intramolecular pi-Ph-Yb interaction, and is a rare example of a mixed valent rare earth aryloxide. Treatment of Er metal with HOmes at elevated temperature (solvent free) affords the homoleptic [Er4(Omes)12] 15, which consists of a tetranuclear array of Er atoms arranged in a 'herringbone' fashion; the structure is stabilized by intramolecular pi-Ph-Er interactions. Reaction of La metal with HOmes under similar conditions yields toluene insoluble "La(Omes)3", which affords 1 following extraction with THF.

ChemInform Abstract: Discovery and Synthetic Applications of Novel Silicon—Carbon Bond Cleavage Reactions Based on the Coordination Number Change of Organosilicon Compounds

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Infrared, Raman and XPS spectroscopic studies of Bi 2O 3–B 2O 3–Ga 2O 3 glasses

Glasses with compositions 60Bi 2O 3–(40−x)B 2O 3–xGa 2O 3 ( x = 5, 10, 15, 20 mol%) are prepared by conventional melting method. The thermal properties are investigated by differential thermal analysis (DTA) and the structures of the glasses were probed by Infrared, Raman and X-ray photoelectron spectroscopy (XPS). The results show that density, refractive index and optical basicity increase with the increase of Ga 2O 3. The glass transition temperature ( T g), the onset crystallization temperature ( T x), Δ T ( T x− T g) decrease with the content of Ga 2O 3. The cut-off edges in ultraviolet and infrared shift to longer wavelength with the increase of Ga 2O 3. On the other hand, the addition of Ga 2O 3 causes a progressive coordination number change of the boron atom from 3 to 4. XPS result indicates both Bi 5+ and Bi 3+ exist in 5 mol% Ga 2O 3 content, while Bi 5+ amounts decrease with the increase of Ga 2O 3 contents. The glass is mainly composed of [BiO 6], [BO 3], [BO 4] and [GaO 4] polyhedra. Glasses are supposed to have layer structure. [BO 3] triangle and [BO 4] tetrahedra may be located between the [GaO 4] tetrahedral and [BiO 6] octahedra to prevent crystallization and to compensate electric charge.

Formula omitted] system: Unraveling of microscopic features by Raman spectroscopy

Raman spectroscopic studies were carried out on a complete range of ceria–gadolinia solid solutions ( Ce 1 − x Gd x O 2 − x / 2 ) to determine the intricate microscopic changes that occur in the system. The system is characterized by the presence of an F-type Raman mode until x ≤ 0.2 , the co-existence of Raman modes of both F-type and C-type in the range ( 0.3 ≤ x ≤ 0.8 ) and mostly C-type Raman mode for x ≥ 0.8 . Several broad modes indicating a high degree of disorder in the F-type lattice could also be observed. As the system ( Ce 1 − x Gd x O 2 − x / 2 ) moves from x = 0.0 to x = 1.0 , the average co-ordination number changes from 8 to 6 which brings about interesting changes at the microscopic level. These changes are readily exhibited by the variation in Raman spectra of various consecutive nominal compositions. This investigation establishes the utility of Raman spectroscopy in convincingly ascertaining the existence of C-type domains in an F-type matrix and vice-versa.

Evidence for electronic gap-driven metal-semiconductor transition in phase-change materials

Phase-change materials are functionally important materials that can be thermally interconverted between metallic (crystalline) and semiconducting (amorphous) phases on a very short time scale. Although the interconversion appears to involve a change in local atomic coordination numbers, the electronic basis for this process is still unclear. Here, we demonstrate that in a nearly vacancy-free binary GeSb system where we can drive the phase change both thermally and, as we discover, by pressure, the transformation into the amorphous phase is electronic in origin. Correlations between conductivity, total system energy, and local atomic coordination revealed by experiments and long time ab initio simulations show that the structural reorganization into the amorphous state is driven by opening of an energy gap in the electronic density of states. The electronic driving force behind the phase change has the potential to change the interconversion paradigm in this material class.

Synthesis and spectral studies on mixed ligand complexes of Cd(II) dithiocarbamates with nitrogen donors: single crystal X-ray structure of bis (4-methylpiperidinecarbodithioato-S,S′)(1,10-phenanthroline)cadmium(II)

The current article describes the synthesis and characterization of the following adducts: [Cd(2-mpipdtc)2(1,10-phen)], [Cd(2-mpipdtc)2(bipy)], [Cd(4-mpipdtc)2(1,10-phen)], [Cd(4-mpipdtc)2(bipy)] (where 2-mpipdtc− = 2-methylpiperidinecarbodithioate anion, 4-mpipdtc− = 4-methylpiperidinecarbodithioate anion, 1,10-phen = 1,10-phenanthroline and bipy = 2,2′-bipyridine). A single crystal X-ray structural analysis was carried out for [Cd(4-mpipdtc)2(1,10-phen)]. IR spectra of the complexes show the contribution of the thioureide form to the structures. Reduction in νC–N(thioureide) for the mixed ligand complexes is attributed to the change in coordination number from four to six and the steric effect exerted by 1,10-phenanthroline or 2,2′-bipyridine. Deshielding of the protons adjacent to nitrogen in the 1H NMR spectra is attributed to drift of electrons from the nitrogen of NR2, forcing electron density towards sulfur via the thioureide π-system. Single crystal X-ray structural analysis of [Cd(4-mpipdtc)2(1,10-phen)] showed that the cadmium is in a distorted octahedral environment with a CdS4N2 chromophore. The presence of 1,10-phenanthroline in the coordination sphere of Cd(dtc)2 increases the Cd–S distances and decreases the S–Cd–S angles. VBS analysis supports the determined structure.

Point defects in sputtered NiO films

The dominant point defects in p-type NiO films were determined by analyzing the coordination number (CN) change with various annealing temperatures and the composition profile of double-layer films deposited individually in oxygen and in argon atmospheres. The results show that the nonstoichiometry of sputtered NiO film is determined by the number of nickel atoms rather than by the number of oxygen atoms. It is concluded that nickel vacancies are the dominant point defects that result in the electrical conductivity of NiO films.

Depth-Dependent Dissociation of Nitric Acid at an Aqueous Surface: Car−Parrinello Molecular Dynamics

The acid dissociation of a nitric acid HNO(3) molecule located at various depths in a water slab is investigated via Car-Parrinello molecular dynamics simulations. HNO(3) is found to remain molecular when it is adsorbed on top of the surface with two hydrogen-bonds, and to dissociate--although not always--by transferring a proton to a water molecule within a few picoseconds when embedded at various depths within the aqueous layer. The acid dissociation events are analyzed and discussed in terms of the proton donor-acceptor O-O hydrogen bonding distance and the configurations of the nearest-neighbor solvent waters of an HNO(3).H(2)O pair. Four key structural features for the HNO(3) acid dissociation are identified and employed to analyze the trajectory results. Key solvent motions for the dissociation include the decrease of the proton donor-acceptor O-O hydrogen bonding distance and a 4 to 3 coordination number change for the proton-accepting water. The Eigen cation (H(3)O(+)), rather than the Zundel cation (H(5)O(2)(+)), is found to be predominant next to the NO(3)(-) ion in contact ion pairs in all cases.

Lattice contraction during amorphization by mechanical alloying

Amorphization has been achieved in blended elemental Fe-based multicomponent alloy powders by mechanical alloying. The effect of Nb addition to the Fe42Ni28Zr10−xNbxB20 alloy in the composition range of 1–6 at. % Nb has been investigated and it was shown that the glass-forming ability (GFA) of the alloys, defined as the milling time required to produce an amorphous phase, improved with Nb addition. The improvement was not regular; the highest GFA was achieved at an Nb level of 2 at. %. Associated with the amorphization process, lattice contraction was noted. The processes of occurrence of the amorphous phase in this alloy system, maximum GFA in the alloy with 2 at. % Nb, and lattice contraction were explained on the basis of the atomic strain model developed first for binary alloys and extended later to ternary and multicomponent alloys, and the change in coordination number with the size ratio of the constituent atoms.

Cuaq+/Cuaq2+ Redox Reaction Exhibits Strong Nonlinear Solvent Response Due to Change in Coordination Number

We have carried out extensive Born-Oppenheimer molecular dynamics simulations to characterize the structure and energetics of the Cu(+)/Cu(2+) redox pair. Our simulations support recent experimental evidence suggesting that Cu(2+) adopts a 5-fold coordination in aqueous solution and not the traditionally assumed octahedral coordination. Cu(+) forms a linear dihydrate structure with a third water molecule occasionally binding in the equatorial plane. We show that the change in ligand coordination number from 2 for aqueous Cu(+) to 5 for aqueous Cu(2+) leads to marked deviations from the linear response assumption underlying Marcus theory of oxidation. The diabatic free energy curves deviate from parabolic behavior and the reorganization free energies for Cu(+) and Cu(2+) are asymmetric and differ by 1.0 eV. The calculated reorganization free energies can semiquantitatively explain the exceptionally small electron self-exchange rate between Cu(+) and Cu(2+) in aqueous solution.

Defining the electronic and geometric structure of one-electron oxidized copper-bis-phenoxide complexes.

The geometric and electronic structure of an oxidized Cu complex ([CuSal](+); Sal = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-(1R,2R)-diamine) with a non-innocent salen ligand has been investigated both in the solid state and in solution. Integration of information from UV-vis-NIR spectroscopy, magnetic susceptibility, electrochemistry, resonance Raman spectroscopy, X-ray crystallography, X-ray absorption spectroscopy, and density functional theory calculations provides critical insights into the nature of the localization/delocalization of the oxidation locus. In contrast to the analogous Ni derivative [NiSal](+) (Storr, T.; et al. Angew. Chem., Int. Ed. 2007, 46, 5198), which exists solely in the Ni(II) ligand-radical form, the locus of oxidation is metal-based for [CuSal](+), affording exclusively a Cu(III) species in the solid state (4-300 K). Variable-temperature solution studies suggest that [CuSal](+) exists in a reversible spin-equilibrium between a ligand-radical species [Cu(II)Sal(*)](+) (S = 1) and the high-valent metal form [Cu(III)Sal](+) (S = 0), indicative of nearly isoenergetic species. It is surprising that a bis-imine-bis-phenolate ligation stabilizes the Cu(III) oxidation state, and even more surprising that in solution a spin equilibrium occurs without a change in coordination number. The oxidized tetrahydrosalen analogue [CuSal(red)](+) (Sal(red) = N,N'-bis(3,5-di- tert-butylhydroxybenzyl)-1,2-cyclohexane-(1R,2R)-diamine) exists as a temperature-invariant Cu(II)-ligand-radical complex in solution, demonstrating that ostensibly simple variations of the ligand structure affect the locus of oxidation in Cu-bis-phenoxide complexes.

Molecular Dynamics Simulations of Liquid Phosphorus at High Temperature and Pressure

By performing ab initio molecular dynamics simulations, we have investigated the microstructure, dynamical and electronic properties of liquid phosphorus (P) under high temperature and pressure. In our simulations, the calculated coordination number (CN) changes discontinuously with density, and seems to increase rapidly after liquid P is compressed to 2.5 g/cm3. Under compression, liquid P shows the first-order liquid-liquid phase transition from the molecular liquid composed of the tetrahedral P4 molecules to complex polymeric form with three-dimensional network structure, accompanied by the nonmetal to metal transition of the electronic structure. The order parameters Q6 and Q4 are sensitive to the microstructural change of liquid P. By calculating diffusion coefficients, we show the dynamical anomaly of liquid P by compression. At lower temperatures, a maximum exists at the diffusion coefficients as a function of density; at higher temperatures, the anomalous behavior is weakened. The excess entropy shows the same phenomena as the diffusion coefficients. By analysis of the angle distribution functions and angular limited triplet correlation functions, we can clearly find that the Peierls distortion in polymeric form of liquid P is reduced by further compression.

Phase transformation during silica cluster impact on crystal silicon substrate studied by molecular dynamics simulation

The process of a silica cluster impact on a crystal silicon substrate is studied by molecular dynamics simulation. At the impact loading stage, crystal silicon of the impact zone transforms to a locally ordered molten with increasing the local temperature and pressure of the impact zone. And then the transient molten forms amorphous silicon directly as the local temperature and pressure decrease at the impact unloading stage. Moreover, the phase behavior between the locally ordered molten and amorphous silicon exhibits the reversible structural transition. The transient molten contains not only lots of four-fold atom but also many three- and five-fold atoms. And the five-fold atom is similar to the mixture structure of semi-Si-II and semi-bct5-Si. The structure transformation between five- and four-fold atoms is affected by both pressure and temperature. The structure transformation between three- and four-fold atoms is affected mostly by temperature. The direct structure transformation between five- and three-fold atoms is not observed. Finally, these five- and three-fold atoms are also different from the usual five- and three-fold deficient atoms of amorphous silicon. In addition, according to the change of coordination number of atoms the impact process is divided into six stages: elastic, plastic, hysteresis, phase regressive, adhesion and cooling stages.

119Sn NMR chemical shift tensors in anhydrous and hydrated Si8O20(SnMe3)8 crystals

(119)Sn chemical shift tensors of crystalline trialkyltin functionalized octameric spherosilicates, Si(8)O(20)(SnMe(3))(8), have been determined by fitting sideband intensities in solid-state magic angle spinning (MAS) NMR spectra. Tin chemical shift parameters are exquisitely sensitive to the presence of water of crystallization. Both hydrogen bonding and incipient oxygen-tin bonding from molecular water impact the local tin environment. Tin chemical shift tensors in the crystalline derivatives reflect the changes in geometry and coordination number at the tin centers. Chemical shift correlations on the crystalline derivatives, with known x-ray structures, are used to infer the tin coordination environment in an amorphous sample.