Joseph W. Kolis

Coordination chemistry of polychalcogen anions and transition metal carbonyls

Abstract This article focuses on the chemistry of heavy polychalcogenides as ligands to transition metal centers. After reviewing some of the general synthetic strategies leading to metal polyselenides and polytellurides, work from the authors labs is discussed, which involves the coordination of polychalcogenide anions to metal carbonyls. It has been found that coordination of polychalcogenide anions to metal carbonyls often results in oxidation of the metal center, with loss of some or all of the carbonyl ligands. This oxidative decarbonylation reaction provides a convenient entry to a wide variety of new and existing metal chalcogenide complexes. The scope and potential of this unusual reaction is discussed.

The chemistry of mixed 1516 main group clusters

This review describes the chemistry of anionic mixed 1516 clusters and their coordination chemistry with transition metals. The focus is on the heavier elements such as sulfides and selenides of phosphorus, arsenic and antimony. A brief introduction with a historical perspective is followed by the chemistry of soluble anionic clusters, including preparative methods and structural characteristics. Solids containing recognizable anionic fragments (Zintl phases) are also described. Bonding is mentioned briefly. Transition metal complexes of these clusters are discussed in some detail and structures and bonding are highlighted. Neglected areas and future prospects are mentioned.

Two novel acentric borate fluorides: M3B6O11F2 (M = Sr, Ba).

Two novel, noncentrosymmetric borate fluorides, Sr(3)B(6)O(11)F(2) and Ba(3)B(6)O(11)F(2), have been synthesized hydrothermally and their structures determined. The compounds are isostructural, crystallizing in space group P2(1), having lattice parameters of a = 6.4093 (13) Å, b = 8.2898 (17) Å, c = 9.3656 (19) Å, and β = 101.51 (3)° for Sr(3)B(6)O(11)F(2) and a = 6.5572 (13) Å, b = 8.5107 (17) Å, c = 9.6726 (19) Å, and β = 101.21 (3)° for Ba(3)B(6)O(11)F(2). The structure consists of a complex triple-ring borate framework having aligned triangular [BO(3)] groups that impart polarity. Fluorine atoms are bound only to the alkaline-earth metals and are not part of the borate framework, resulting in a vastly different structure from those of the hydrated borates Sr(3)B(6)O(11)(OH)(2) and Ba(3)B(6)O(11)(OH)(2) with similar formulas. The title compounds are transparent to nearly 200 nm, making them potentially useful for deep-ultraviolet nonlinear-optical applications.

Diels-Alder reactions using supercritical water as an aqueous solvent medium

Abstract A variety of Diels-Alder reactions have been performed in supercritical water as a reaction medium. The rapid reaction of Diels-Alder reactions of cyclopentadiene and various electron poor dienophiles such as diethyl fumarate and acrylonitrile is observed in supercritical water, and leads to high yields of clean products without added catalysts.

Materials Chemistry and Bulk Crystal Growth of Group III Nitrides in Supercritical Ammonia

Reasonably sized crystals of aluminum and gallium nitrides can be grown in supercritical ammonia using chloride and amide as the mineralizer. Best growth was achieved at 380°C in ammonia at 40,000 psi (270 MPa). Under these conditions crystals as large as 0.4 mm could be grown over several days. Attempts to optimize the identity and concentration of the mineralizer, and the acidity of the solution, led to several new products including A1F 3 (NH 3 ) 2 .

Synchrotron white beam topography characterization of physical vapor transport grown AlN and ammonothermal GaN

Structural defects in AlN single crystals grown by the sublimation method and GaN single crystals grown by the ammonothermal method are characterized by synchrotron white-beam X-ray topography in conjunction with optical microscopy. AlN platelets are either of (1120) or (0001) type depending on the growth conditions. Dislocation densities of the order of 10 3 cm -2 or lower are observed in some crystals. X-ray topographs reveal the presence of growth sector boundaries, inclusions, and growth dislocations that indicate slight impurity contamination. The 2H crystal structure of GaN single crystals obtained by the ammonothermal method was verified by Laue X-ray pattern analysis. GaN crystals grown are of the order of 1 mm in size and are either (0001) platelets or [0001] prismatic needles. Generally, prismatic needles are characterized by lower degree of mosaicity than (0001) platelets.

Spectroscopic properties of Er3+ and Eu3+ doped acentric LaBO3 and GdBO3

This work studies the spectroscopic behavior of Eu3+-doped and Yb3+/Er3+-codoped single crystals of orthorhombic LaBO3 and rhombohedral GdBO3. Emissions from Er3+ at ∼1535 nm are shown to exhibit multiple narrow linewidth emissions. Luminescence from the 5D0→7F1, 7F2 transitions of Eu3+ is found to depend on the choice of LaBO3 or GdBO3 as a parent phase in a well-defined manner. Phonon sideband spectroscopy of the Eu3+ 5D2 excitation, corroborated using Raman spectroscopy, indicates that the highest energy phonon is less than 1400 cm−1 for the LaBO3 and less than 1010 cm−1 for the GdBO3. Further, absorption spectrum to 190 nm is provided for the GdBO3 clearly showing the 6I manifold, and the rarely seen 6D levels. Excitation of the 6D7/2 state at 250 nm in GdBO3 is shown to yield a strong ultraviolet emission centered at 314 nm. This work marks the lanthanide borates as candidate single crystals for active and nonlinear materials for UV, visible, and telecommunication band applications.

Solution chemistry of arsenic selenides: Synthesis, spectroscopy and the x-ray structures of [PPh4]2[AsnSe6], n = 2,4

Abstract As4Se4 and As4Se3 do not retain their solid-state structures in solution. Dissolution of As4Se4 in en/DMF (en = ethylenediamine, DMF = dimethylformamide) causes the cleavage of an AsAs bond and the formation of the As4Se62− anion. In the presence of excess polyselenide ions the remaining AsAs bond also breaks and the As2Se62− anion is produced. Reduction of As4Se4 by potassium in DMF in the presence of PPH4Cl also produces the As4Se62− anion. [PPh4]2[As4Se6] crystallizes (− 120°C) in the orthorhombic space group Pbca with cell dimensions a = 11.272(1), b = 19.817(2), c = 43.958(9) A, Z = 8. The As4Se62− anion resembles a basket with AsSe exocyclic bonds being the handles. [PPh4]2[As2Se6] crystallizes in the monoclinic space group P21/n with cell constants a = 10.817(2), b = 13.690(4), c = 16.298(3) A, β = 93.96(2)°, Z = 2. The As2Se62− ion has an As2Se4 ring in a trans-chair conformation with a terminal selenium atom on each arsenic atom.

Hydrothermal synthesis and crystal structures of two novel acentric mixed alkaline earth metal berylloborates Sr3Be2B5O12(OH) and Ba3Be2B5O12(OH).

The synthesis and structure of the isostructural acentric compounds Sr(3)Be(2)B(5)O(12)(OH) (1) and Ba(3)Be(2)B(5)O(12)(OH) (2) are reported for the first time. These compounds crystallize in the space group R3m, and the unit cell parameters are a = 10.277(15) Å and c = 8.484(17) Å for 1 and a = 10.5615(15) Å and c = 8.8574(18) Å for 2. The structures consist of a network of [Be(2)B(4)O(12)(OH)] units interwoven with a network consisting of MO(9) polyhedra (M = Sr, Ba) and BO(3) triangles and exemplify how acentric building blocks such as [BO(3)](3-), [BO(4)](5-), and [BeO(4)](6-) can be especially suitable to build noncentrosymmetric long-range structures. Both networks are centered on the 3-fold rotation axis and present themselves in alternating fashion along [001]. Acentricity is imparted by the alignment of the polarities of BO(3) and BeO(4) environments. Infrared spectroscopy has been used to confirm the local geometries of B and Be, as well as the presence of hydroxide in the crystal structure. Another interesting feature of these compounds is the presence of disorder involving Be and B at the tetrahedral Be site. The degree of the disorder has been confirmed by observing a noticeable shortening of average Be-O bond distances.

Hydrothermal Synthesis and Crystal Structure of Two New Hydrated Alkaline Earth Metal Borates Sr3B6O11(OH)2 and Ba3B6O11(OH)2

Two new hydrated borates Sr(3)B(6)O(11)(OH)(2) (1) and Ba(3)B(6)O(11)(OH)(2) (2) were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by IR, powder XRD, and DSC/TGA. Compound 1 crystallizes in the triclinic space group P-1 with unit cell parameters of a = 6.6275(13) Å, b = 6.6706(13) Å, c = 11.393(2) Å, α = 91.06(3)°, β = 94.50(3)°, and γ = 93.12(3)°, while compound 2 crystallizes in the noncentrosymmetric monoclinic space group Pc with a = 6.958(14) Å, b = 7.024(14) Å, c = 11.346(2) Å, and β = 90.10(3)°. In spite of the differences in symmetry and packing of the borate chains, both structures consist of the same fundamental building block (FBB) of a [B(6)O(11)(OH)(2)](-6) unit and three unique alkaline earth metal atoms.