Phase range of the type-I clathrate Sr8Al(x)Si(46-x) and crystal structure of Sr8Al10Si36.

Samples of the type-I clathrate Sr(8)Al(x)Si(46-x) have been prepared by direct reaction of the elements. The type-I clathrate structure (cubic space group Pm3n) which has an Al-Si framework with Sr(2+) guest atoms forms with a narrow composition range of 9.54(6) ≤ x ≤ 10.

Crystals in which some metal atoms are more equal than others: inequalities from crystal packing and their spectroscopic/magnetic consequences.

Crystal structures of the heterometallic compounds CrCrFe(dpa)(4)Cl(2) (1), CrCrMn(dpa)(4)Cl(2) (2), and MoMoMn(dpa)(4)Cl(2) (3) (dpa = 2,2'-dipyridylamide) show disorder in the metal atom positions such that the linear M(A)[quadruple bond]M(A)···M(B) array for a given molecule in the crystal is oriented in one of two opposing directions. Despite the fact that the direct coordination sphere of the metals in the two crystallographically independent orientations is identical, subtle differences in some metal-ligand bond distances are observed in 1 and 3 due to differences in the orientation of a solvent molecule of crystallization. The Fe(II) and Mn(II) ions serve as sensitive local spectroscopic probes that have been interrogated by Mössbauer spectroscopy and high-field EPR spectroscopy, respectively.

A ditetrylyne as a π-electron donor: synthesis and characterization of [AgAr'GeGeAr'](+)SbF6(-) and [Ag2Ar'GeGe(F)Ar'](+)SbF6(-) (Ar' = C6H3-2,6(C6H3-2,6-Pr(i)2)2).

The reaction of a digermyne Ar'GeGeAr' (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)) with AgSbF(6) at -40 °C forms the complex (AgAr'GeGeAr')(+)SbF(6)(-), which provides the first example of a heavier group 14 element alkyne analogue behaving as a π donor to a transition metal. The cation (AgAr'GeGeAr')(+) is best described as a hybrid of a π-complex and a σ-metallacyclopropene structure.

When VSEPR fails: experimental and theoretical investigations of the behavior of alkaline-earth-metal acetylides.

The synthesis, structural, and spectral characterization as well as a theoretical study of a family of alkaline-earth-metal acetylides provides insights into synthetic access and the structural and bonding characteristics of this group of highly reactive compounds. Based on our earlier communication that reported unusual geometry for a family of triphenylsilyl-substituted alkaline-earth-metal acetylides, we herein present our studies on an expanded family of target derivatives, providing experimental and theoretical data to offer new insights into the intensively debated theme of structural chemistry in heavy alkaline-earth-metal chemistry.

Calcium complexation by corticosteroids.

Cortisone and hydrocortisone form calcium complexes of 2:1 steroid/Ca(2+) stoichiometry in solution, with formation constants of 201 +/- 1.7 and 184 +/- 1.7 M(-2), respectively-roughly half the value seen for a simple aromatic alpha-hydroxy ketone, phenacyl alcohol (341 +/- 10.

Synthesis, structure, and properties of BaAl2Si2.

Single crystals of BaAl2Si2 were grown from an Al molten flux and characterized using single-crystal X-ray diffraction at 10 and 90 K and neutron diffraction at room temperature. BaAl2Si2 crystallizes with the alpha-BaCu2S2 structure type (Pnma), is isostructural with alpha-BaAl2Ge2, and is an open 3D framework compound, where Al and Si form a covalent cagelike network with Ba2+ cations residing in the cages. BaAl2Si2 has a unit cell of a=10.

Transannular Anti-Michael Addition: Formation of 4H-Pyrazolo[5,1-c]thiazines.

The reaction of 2-(diphenylmethylene)thietan-3-one (2) with 1,2,4,5-tetrazines (3a-c) in KOH/MeOH/THF gives 4H-pyrazolo[5,1-c]thiazines (7a-c). This no vel condensation reaction proceeds via the intermediacy of an 8-(diphenylmethylene)-2H-1,4,5-thiadiazocin-7(8H)-one (5), which undergoes a multi-step rearrangement including a rare anti-Michael addition.

A novel route to fully substituted 1H-pyrazoles.

A novel one-step synthesis route to fully substituted pyrazol-4-ols is reported. This simple yet nonobvious method for the construction of pyrazol-4-ols by the condensation-fragmentation-cyclization-extrusion reactions of thietanones with 1,2,4,5-tetrazines is reported. All of the elements of the thietanone except its sulfur are incorporated in these novel products.

New 3-oxo-chol-4-en-24-oic acids from the marine soft coral Eleutherobia sp.

Two novel cholic acid derivatives and three known steroids were isolated from an octocoral Eleutherobiasp. from Pohnpei Micronesia along with the known briareins minabein-1 (6), minabein-4 (7), minabein-6 (8), minabein-8 (9), and minabein-9 (10). X-ray crystallographic analysis of the known compound minabein-4 allowed assignment of its correct relative and absolute stereochemistry.

Probing the limits of the Zintl concept: structure and bonding in rare-earth and alkaline-earth zinc-antimonides Yb9Zn4+xSb9 and Ca9Zn4.5Sb9.

A new transition metal Zintl phase, Yb(9)Zn(4+x)Sb(9), was prepared by high-temperature flux syntheses as large single crystals, or by direct fusion of the corresponding elements in polycrystalline form. Its crystal structure was determined by single-crystal X-ray diffraction. Its Ca-counterpart, hitherto known as Ca(9)Zn(4)Sb(9), and the presence of nonstoichiometry in it were also studied.

Low-temperature water reconstruction in concanavalin A, with implications for controlled protein crystal annealing.

Flash-cooled crystals of the I222 form of concanavalin A undergo a sharp non-destructive non-reversible phase transition upon warming to between 160 and 165 K, characterized by an anomalous increase in unit-cell volume. The expansion is anisotropic and primarily affects the b and c axes. Three sets of 1.