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The different size and site preferences of Mg and Zn in newly synthesized structural phases of Ae[M.sub.x][In.sub.4-x] (Ae = Sr, Ba; M = Mg, Zn) with Ba[Al.sub.4]-type features is discussed.

The synthesis and structural characterization of [Ca.sub.4][Au.sub.10][In.sub.3], the first ternary derivatives of the [Zr.sub.7][Ni.sub.10] structure is described. The structure exhibits a complex [[Au.sub.10][In.sub.3]] polyanion framework containing remarkable sinusoidal Au layers.

The solid-state reactions in welded Ta tubes at high temperature were used to synthesize the [M.sub.2]B[a.sub.2]S[n.sub.6] (M = Yb, Ca) compound. The electronic structures calculated indicate that the compounds are metallic with a deep pseudogap at the Fermi level.

The production of the ternary polar intermetallic phase [Mg.sub.5.231(8)][Sm.sub.0.231(8)][Sb.sub.4] from solid state reactions at 700-850 degrees Celsius in sealed Ta or Nb containers when the synthetic conditions took into account its characteristic incongruent melting point is reported. The results present the first example of a superstructure of a[Mg.sub.3][Sb.sub.2]-like structure with a doubled c axis induced by ordering a mixture of the larger divalent Sm and Mg ions separately within alternate layers of octahedral sites.

Three new compounds in the ternary Ba-(An,Hg)-(In,TI) systems are reported that are isostructural with orthorhombic CeCu2, a lower-symmetry relative of the CaIn2 type. The relativistic effects for the heavier Au and Hg are responsible for decreases in lattice parameters and bond lengths from BaIn2 to those in isostructural BaAu(sub 0.36)(4)In(sub 1.64)(4) and BaHg(sub 0.82)(2)In(sub 1.08)(2).

The phases LiMgCa(sub 10)Sb(sub 9), Mg(sub 2)Ca(sub 10)Sb(sub 9), and Li(sub 1.38(2))Sb(sub 9) are synthesized by high-temperature solid-state means and characterized by single-crystal means and property measurements. The LiMgCa(sub 10)Sb(sub 9) compound is correspondingly diamagnetic and presumably a semiconductor.

The syntheses, structural characterizations, and the electronic structure of and chemical bonding within the new phase region is reported. The structure shows substantial differences from related A(sub 15)Tl(sub 27) (A = Rb, Cs) in which the cation A that centers a six-membered ring of Tl(sub 11) fragments is replaced by M(sub 3).

The reaction of elemental In, Pb, or K, or Rb within welded Ta containers at 900 degree Celcius followed by subsequent annealing at 35 degree Celcius gives the new phases A(sub5)InPb(sub)8 (A = K, Rb). Wades rules for counting bonding electron states in a given class of clusters indicate that the charge assigned to an ideal deltahedral tetral cluster is independent of its nuclearity.

The ratio of Cu and Ga are changed to acquire four electrons in order to tune the primitive composition of the ternary Mg2Cu6Ga5 phase to a quasicrystalline approximant. However, these efforts produce the Mg35Cu24Ga53 compound consisting of a three-dimensional cubic network, whose synthesis, structure and bonding analysis are presented.

Structural stabilization among the three compounds namely K34In92.30Li2.70, K14Na20In91.82Li13.18 and K14Na20In96.30 reveals an intimate relationship between structure and valence electron requirements. The electronic tuning within the complicated network structure is realized by substitution of part of the iridium by electron-poorer lithium atoms.

The synthesis, structure and bonding of the nonclassical Zintl phase K5As3Pb3 are described. It is shown that the nonclassical bonding is encountered most often in more electron-deficient cluster systems, particularly with triel (group 13) members.

The bcc structure contains the multiply endohedral cluster polyhedra shown around each lattice point, the last two shells being shared with like neighbors. Atom site preferences parallel the greater electronegativity of Cd over Tl.

Results describe the syntheses of the quaternary lanthanide halide cluster compounds containing transition metal interstitials and alkali or alkaline-earth metal ions using high temperature solid state techniques. The compounds exhibit rhombohedral structure and semiconductor activity.

Research has been conducted on KNa (sub)3 In (sub)9. The results of the single-crystal X-ray diffraction analysis demonstrate that this compound crystallizes in the orthorhombic system which contains indium network constructed of empty indium icosahedra layers.

Research examines the insertion of a palladium atom into a known triel element cluster leading to the formation of palladium-centered thallium clusters. Data indicate that in such clustering process the atom and orbital sizes of the two components as well as the anionic characteristics of thallium appear to be important.

Research has been conducted on the heterometallic compounds from the orthorhombic family. The synthesis and structures of these compounds have been carried out and their electronic structures have been investigated and are discussed.

The synthesis and characterization of the new BaTi3 compound is done by physical property measurements and electronic structure calculations. The unique geometric features of the anionic thallium layers gives rise to unusual competition between inter and intracluster bonds.

Research has been conducted on the compounds containing square pyramidal tin and lead Tt (sub)5 polyanions. Results indicate that these compounds have been obtained via the direct fusion of the alkaline-earth or rare-earth metal-tetrel systems followed by slow cooling.

Research has been conducted on the formation of K (sub)2 SrIn (sub)7. The direct fusion of the neat elements in a niobium tube has been investigated, and the results of the single-crystal X-ray diffraction analysis revealing that K (sub)2 SrIn (sub)7 crystallizes in the orthorhombic system are presented.

Research has been conducted on the K (sub)6 Tl (sub)2 Sb (sub)3 with the heteroatomic anionic chains discovered in the K-Tl-Sb system. The results indicate that the active metal-thallium-pnictide compound exhibits Tl-Tl bonding.

Open-shell Sr3In5 was synthesized and characterized and an unusual electron deficiency beyond the Zintl boundary was observed.

A series of isostructural compounds R5Ga3 (R = Sc, Y, Ho, Er, Tm, Lu) are shown to have a new distorted version of the familiar Mn5Si3 structure type. The electronic calculations reveal that the distortion and formation of Ga2 anions allows a significant displacement of antibonding dimer levels above E(sub F) and an appreciable lowering of Ga-Ga and Ga-Sc states just below E(sub F).

The most egregious of the errors committed or possible for Cr5B3-like phases, those that are uniquely stabilized by hydride (or fluoride) are reported. The new ternary phases are generally Pauli-paramagnetic, evidently with pi electrons from the characteristic tetrelide dimers in this structure type at least partially delocalized into the conduction band and the Sn-Sn bonds appear correspondingly shortened on oxidation.

The synthesis and characterization of centered cluster halides and tellurides of the earliest transition metals is summarized. It also looks into the broad interstitial chemistry of the widespread group of metallic transition-metal phases with a Mn5Si3 type structure.

Research shows that the metal-metal bonding in the transition metal chalcogenides is facilitated by the crystallization of these compounds in the Fe(sub)2P structure type called Zr(sub)6CoAl(sub)2. Results demonstrate that the chalcogenides containing metal substituents exhibit structural and electronic flexibility and the metal-metal bonding is one dimensional in character.

The basic building blocks in these novel anionic chains are the pentagonal antiprisms centered by Cd. Band calculations and resistivity and magnetic susceptibility measurements clarify the unusual architecture and properties. Additional four-bonded Tl atoms on one side of the chain make the structure acentric.

Research has been conducted on the K (sub)10 Tl (sub)7. The synthesis of the compound by direct fusion of the elements has been carried out.

Sc(sub9)Te(sub2) structure was investigated, comprising distorted columns of scandium metal and a corrugated layer of tellurium atoms, separating rumpled metal layers.

The authors discuss the reactions in the La-Br-Z system where Z=Fe, Ru and Os metal atoms. Results demonstrate that only Os has led to the characterization of La (sub)48 Br (sub)81 Os (sub)8 phase.

A new compound containing the isolated gallium clusters Ga10Ni10- was revealed through the exploration of the sodium-gallium-nickel system. The single-crystal X-ray diffraction studies of Na10Ga10Ni demonstrate that it is isostructural with K10In10Ni. A strong tendency to form extended structures was observed which makes the formation of isolated Ga10Ni10- units in Na10Ga10Ni an even more interesting result.

Research was conducted to examine a novel network design which provides what appears to be an ideal connectivity for intercluster electron delocalization. The syntheses of alpha-K4R6I14Os (R = La, Pr), with their unusual cluster connectivities and all the delocalization implications thereof, clearly show how the introduction of alkali metals can lead to the formation of more open and less bridged structures. The 2D band calculations clearly shows the increased dispersion and delocalization that can be derived in the 2D-planar net of iodine-bridged clusters, which was the first unexpected feature of the new cluster structure.

The synthesis of a new compound which is a nominal polymorph of the novel tetragonal (alpha-)K4-La6I14Os, in which undistorted octahedral La6(Os)I(super i)(sub 10) units are interbridged by I(super i-a)(sub 4/2) into a new planar network, is reported. The synthesis emphasizes the possibility of new structures that can be produced by subtle variations in such quaternary systems.

The structure of Sc(sub 5)Ni(sub 2)Te(sub 2) prepared by high-temperature solid-state techniques was investigated. The structure contained pairs of eclipsed zigzag chains of nickel atoms that were coated by scandium atoms and demarcated from other chains by tellurium atoms. The structure was isotypic with that of Hf5Co(sub 1+x)P(sub 3-x) but shifted atomic positions and a different ordering of the main group and late transition elements gave it a clearly one-dimensional character.

The synthetic studies, a single-crystal X-ray structure determination and some electrical and magnetic property measurements on the new Yb(sub 36)Sn(sub 23) with its novel mixture of monomeric, dimeric and hexameric tin anions are described. The compound crystallizes in tetragonal space group P4/mbm with a = 12.3869(5) angstroms, c = 22.935(1) angstroms, Z = 2. The structure has a linear tin hexamer, five dimers, and seven isolated tin atoms per formula unit.

A study was conducted to analyze the presence of the Tl8Cd3(super 10-) derivative of Tl11(super 7-) in the title compound Na9K(sub 16-)Tl18Cd3. The title compound was determined by the reaction of the constituent elements. Magnetic susceptibility measurements were then carried out on Na9K16Tl18Cd3 in the field of 3 T using the Quantum Design MPMS SQUID magnetometer. In addition, the EHMO program was utilized to carry out bonding and charge distribution computations.

A study on the syntheses, crystal structures and magnetic properties of four novel cubic R20X28Z4-type compounds with R16Br20Z4 oligomers is presented. These oligomers are interbridged via bromine to R4Br8 tetrahedra. The systematic breathing distortion of R16X20Z4 clusters increases in the order Y-I, Y-Br, Sc-Br(Ru,Os,Ir) to Sc-Br-Mn and Gd-I-Mn. These discrepancies are dependent not only on the sizes of the atoms but also on significant variations in orbital energies.

A study relating to classical metallic Zintl phases has resulted in the discovery of another thallium cluster type Tl77- with another example of a the cluster Tl99- in the quaternary phase Na12K38Tl48Au2. Large monoatomic Au- anions were required to stabilize a structure with a relatively large number of alkali-metal cations per cluster. The structure, properties and bonding of the title compound and the clusters are discussed.

A study of the possibilities that hydrogen or other light main-group nonmetals might stabilize alkali- or alkaline-earth-metal compounds with group 13-15 elements has led to the discovery of a highly unusual compound Ca13Al14. It was also found that the triclinic phase Ca8Al3 could also be formed in the absence of either hydrogen or lithium. The synthesis, crystal structure determinations and some bonding aspects and properties of these two compounds are discussed.

Reactions between alkali metals and the triel elements in the presence of gold and electron-rich tin produced the compound K4-(AuTlSn3). It was observed that the repeat unit in the AuTlSn3- chain was one electron richer than the average Tl- oxidation state known in the homoatomic anion in (K+)6Tl(sub 4)(super 6). Moreover, the compound also exhibits a structure wherein the heavy elements form infinite one-dimensional chains.

Studies conducted on thallium have found the metal to be highly productive in the creation of alkali-metal compounds containing different, innovative thalium clusters, networks of clusters or both. Following experiments on some mixed Tl-Sn anionic systems, a study to derive heteroatomic cluster anions by introducing pnictogen arsenic into the Rb-Tl compounds eventually resulted in the oxidation of the Ta container and the creation of the Rb5TaAs4Tl2 compound. The synthesis and structural and bonding properties of this unusual compound are discussed.

The structure of a lanthanum iodide (La2INi2) crystal was characterized and compared with the La2IFe2 structure in terms electronic band calculations and orbital populations mediating structural and bonding alterations in phases of atypical layer stacking sequence. The difference between the two structures were the iodine ordering and Z-slab puckering although the structures were prominently linked with each other. The La2IFe2 contained a single type of iron atom in a puckered layer while the La2INi2 needed two non-equivalent nickel atoms.

A novel structure for isolated clusters that is generated by cation requirements is presented. A new monoclinic structure type for K2La6I12Os results from the presence of the large Os interstitial and two relatively small K+ counteractions. The structure contains nominal octahedral metal clusters defined by an enclosed Os atom that lies on an inversion center and three crystallographically distinct metal atoms.

The syntheses of five compounds Ba21Ge2O5H24 (Tt = Ge, Si) and Ba21Tr2O5Hx (Tr = Ga, In, Tl, x ~ 22), in which hydrogen is an essential element, and the corrected structure of Ba21Ge2O5H24, are presented. X-ray single-crystal and neutron powder diffraction means were used to redetermine the heavy-atom structure of Ba21Ge2O5H24 at room temperature while time-of-flight neutron diffraction method was used to locate 24 independent deuterium atoms. Results indicate that the analogues Ba21tr2O5Hx, Tr = Ga, In, Tl, are isotypic with the heavy-atom structure of the title phase.

The compounds Sc8Te3 and Y8Te3 were synthesized by high-temperature solid-state methods. Their structures were determined by single-crystal and powder X-ray diffraction techniques. The layered structure of the said compounds were observed to be made of a complex network of chains of trans-edge-sharing metal octahedra condensed into two kinds of corrugated sheets that are kept apart by tellurium.

Research was conducted to prepare a derivative of the unknown W5Si3-type Ca5Sn3. The structure has an inherent problem of short A-A separations along the tetrahedral chains that lie on the side faces of the tetragonal cell and partial substitution of a smaller cation like Mg2+ was more appropriate. The reaction yielded a second compound in the process, Ca6.2Mg3.8Sn7. Results indicate the effect that different cations have on phase stability. Findings also suggest the existence of a new type of infinite tin chain derived from square-planar tin units. Its synthesis and crystal structure are described.

Alkali-metal-gallium systems have a rich novel cluster chemistry. A discrete gallium cluster has been reported as tetrahedral units observed in Casub11Gasub7. There is a trend towards discrete cluster species, continuing with thallium. Alkali-metal-gallium systems for isolated clusters have been reexamined, and the first example in Cssub8Gasub11 is reported.

Two sets of quaternary cluster phases containing Asub4Brsuper3+ions were afforded from reactions of ABr, Zr, ZrBrsub4 and a Z element in Ta containers at 850 degress C. Cubic (Asub4Br)sub2Zrsub6(Z)Brsub18 phases occurred for certain combinations. Both Asub4Brsuper3+ion examples exhibited short central Br-A bonds.

The compound Na5Sn13 is produced in the sodium-tin system in high yield after prolonged reaction of a quenched mixture at 280 degrees C in a Ta container. The compound has a complex three-dimensional structure composed primarily of 4-bonded atoms in interbonded pentagons. Based on Zintl-Klemm electron-counting formalisms, the compound has a closed-shell electronic configuration with the number of 3-bonded Sn- equal to the number of sodium cations. Property measurements indicate the compound to be diamagnetic.

A new family of hydrogen-stabilized Zintl compounds, namely, Ca3SnH2, Ca3PbH2, Yb3SnH2 and Yb3PbH2, were synthesized. Ca3SnH2 and Ca3PbH2 were synthesized by reacting CaH2 with Ca and Sn or Pb at 1100 degrees C followed by slow cooling. The same was true for Yb3SnH2 and Yb3PbH2. The compounds were characterized by single-crystal X-ray diffraction. The distortion noted in Ca3SnH2 and its corresponding oxide was attributed to the doubling of the interstitial count in the structural regime dominated by more-or-less close-packed Ca3Sn layers.