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We report the crystal structure of a spiro-bis(1,9-disubstituted-phenalenyl)boron cation ( 2 + ) and by comparison with the structures of a series of radicals we conclude that the changes in bond lengths in the radicals compared to those of the corresponding cation can be qualitatively predicted by the sign of the partial bond order of the singly occupied molecular orbital (SOMO), which contains the additional electron. By use of this information, we can analyse the structures of the π-dimer radicals 1 and 2 and ascertain the location of the unpaired electron in these compounds. Where these radicals exist as paramagnetic π-dimers (high-temperature regime), the unpaired electrons reside mainly in the phenalenyl units not directly involved in the π-dimer interaction. At low temperatures, where the diamagnetic π-dimers exist, the electrons localise in the phenalenyl units directly involved in the π-dimer, but there still exists some degree of delocalisation of the electrons to the other halves of the molecules. We postulate that the increase in delocalisation of the unpaired electrons is related to the increase of the conductivity by about two orders of magnitude as the electrons spin pair.

Reactions of bis[diphenyl-3-(4-methoxyphenylsydnonyl)]phosphine palladium chloride and amines yielded trans-amminedichloropalladium complexes, which were characterized by spectroscopic techniques (compounds 5–9) and X-ray diffraction (compounds 5 and 7). Bond lengths of PC(10), P-(16) decrease more than that of P-(1) after the complex is formed, suggesting that the phenyl rings are able to contribute more electron density to phosphorus for binding with Pd(II) than the sydnone ring. The equilibrium constants and rate constants for the reaction between complex 4 and amines depend not only on the basicity but also on the steric size of amines used.

A simple and general route to the synthesis of cobaloxime with mixed dioxime ligands, XCo(L)(L′)Py, L,L′=dmgH/dpgH and chgH/dpgH; X=Cl, Br, NO2, N3, has been described. These compounds are reported for the first time. The synthesis is confirmed by the X-ray structures of N3Co(dmgH)(dpgH)Py and N3Co(chgH)(dpgH)Py. The cis and trans effects on these complexes and on XCo(L)2Py (L=dmgH, chgH, dpgH; X=Cl, Br, NO2, N3) complexes have been studied by 1H-, 13C-NMR, UV, and X-ray. For a range of X ligands, a clear trend between the 1H, 13C chemical shifts of the equatorial and axial ligands as well as with the Co–dioxime CT band has been observed. The analysis of the 13C values and X-ray data shows that one dioxime wing effects the other dioxime wing in the mixed dioxime complexes.

A simple and general route to the synthesis of organocobaloxime with mixed dioxime ligands, RCo(dmgH)(dpgH)Py and RCo(chgH)(dpgH)Py, has been described. The 13C-NMR chemical shifts have been analysed to see whether one dioxime wing has any effect on the other dioxime wing. The first crystal structure of an organocobaloxime with mixed dioxime ligand in the same complex, BnCo(dmgH)(dpgH)Py and BnCo(chgH)(dpgH)Py, is reported.

Dissolution of [CpRu(PPh 3 )(SC 4 H 8 ) 2 ]CF 3 SO 3 in thietane/CH 2 Cl 2 with stirring yields the title compound [CpRu(PPh 3 )(SC 3 H 6 ) 2 ]CF 3 SO 3 ( I ). The single crystal X-ray structure shows a disparity in the puckering of the two thietanes. One thietane ligand is near-planar, with torsion angles of ±1.5(5)° for CSCC and ±1.8(4)° for CCCS; the second thietane ligand of I has torsion angles of ±21.0(4)° for CSCC and ±25.0(3)° for CCCS. Compound I contains both the largest and the smallest torsion angles for any complex reported. Theoretical calculations were carried out for both thietane and for I using the gamess and gaussian 98 packages.

A synthetic scheme leading to the (X)(Y)bis(1,2-cyclohexanedionedioximato)cobalt(III) complexes, where X=Cl, N 3 , ClCH 2 , CH 3 , C 2 H 5 and Y=PPh 3 and Py is reported. The complexes have been characterized by the usual spectroscopic techniques and have been compared with the reported analogous compounds having other dioximes as the equatorial ligands. The first crystal structure of an inorganic cobaloxime with 1,2-cyclohexanedionedioxime (Nioxime) is reported. For a range of X ligands, a clear trend between 31 P, 13 C, 1 H chemical shifts of the equatorial and axial ligands as well as with the Co→chgH charge transfer band has been observed.

The structure of 4,4'-bipyridinium diiodide has been determined. The diprotonated cation possesses crystallographic inversion symmetry with the pyridyl rings coplanar. The crystal packing is dominated by weak but directional N-H···I (N···I distance of 3.47(2) A) and C-H···I (C···I distances of 3.74(3)3.77(3) A) interactions to give layers of ions. The layers stack parallel to the (101) direction and are linked together by an additional C-H···I interaction (C···I distance of 3.816(5) A). Crystal data: triclinic, P-1 (No. 2), a = 8.2940(13), b = 8.3842(11), c = 5.0978(8) A, a = 93.761(11)°, s = 112.281(12)°, ? = 106.887(11)°, V = 307.63(8) A3, Z = 1, Scalc = 2.22 g/cm3. Final residual values based on 997 observed (I > 2s(I)) reflections: R = 0.026, Rw = 0.034.

A comparative study of the structural parameters of bis(dioxime) vitamin B12 models reveal an interesting squeezing of the metallabicycle. The lateral compression and the butterfly bending angle have a common origin in the steric bulk of the dioxime substituents. The first crystal structure of an organocobaloxime with cyclohexanedionedioxime(chgH) as the equatorial ligand is also reported. The compound MeCo(chgH)2Py crystallises in the monoclinic system, with the space group P21/n with Z=4 and unit cell parameters a=8.7074(9), b=9.3989(8), c=23.886(2) A and β=91.862(8)°.

The isolation and characterization of the trimethylenesulfide-coordinated complex, [CpRu(PPh3)2(SC3H6)]CF3SO3, is reported. The structure of [CpRu(PPh3)2(SC3H6)]CF3SO3 was determined by X-ray diffraction techniques: monoclinic space group I2/a, a=23.864(10), b=14.233(3), c=24.385(7) A, β=97.10(3)°, Z=8, R=0.046, Rw=0.065. The Ru is attached to two triphenylphosphine ligands, a cyclopentadienyl and the trimethylenesulfide. The Ru-S distance is 2.3459(20) A.

In the quasibinary system MnIn 2 S 4 -MnIn 2 Se 4 a series of solid solutions of general formula MnIn 2 S x Se 4- x exists for 2.4 ≥ x ≥ 0.2 with the layered MgAl 2 S 4 structure. The samples have been characterized by X-ray powder diffraction and investigated by electrical measurements and diffuse reflectance spectroscopy. The compounds are semiconductors with optical band gaps varying between 1.6 and 1.2 eV depending on x . From Arrhenius plots of the conductivity data at least two different activation energies E a can be obtained: in the temperature interval from 50 to 200°C we find E a = 0.5 eV, independent of the composition of the samples, while in the high temperature region from 200 to 400°C, E a varies with x from 1.35 to 0.56 eV.

The isolation and characterization of two mercaptan complexes of the general formula [CpRu(PPh3)2(RSH)]BF4, where R=benzyl and phenethyl, were undertaken to model the substrate/catalyst interaction of the hydrode-sulfurization (HDS) process. The IR data show a shift in the SH stretching frequency upon coordination. The structure of the [CpRu(PPh3)2(C6H5CH2CH2SH)]BF4 complex was determined by X-ray diffraction techniques: monoclinic space group P21/n, a=15.317(4), b=13.924(9), c=21.815(7) A, β=95.20(2)°, Z=4, R=0.057, Rw=0.073. The Ru is attached to two triphenylphosphine ligands, a cyclopentadienyl and the phenethylmercaptan. The Ru-S distance is 2.369(2) A and the S-H distance is 1.18 A.

The systems MnGa2S4MnV2S4, MnGa2S4MnTi2S4 and the corresponding magnesium systems MgGa2S4MgV2S4 and MgGa2S4MgTi2S4 were studied by x-ray diffraction methods on quenched powder samples. In all four systems new quaternary compounds crystallizing in a layered structure have been obtained. MgGa1.6Ti0.4S4 (a = 370.9, c = 1219.1 pm) adopts a structure of α-FeGa2S4-type while MnGa1.6Ti0.4S4 (a = 370.9, c = 1219.0 pm) and MnGa1.8V0.2S4 (a = 370.2, c = 3652 pm) are of ZnIn2S4(IIIa)-type at 700 °C and undergo a phase transition to the α-FeGa2S4 type at 960 °C. Samples of MgGa1.6V0.4S4 consist of a mixture of both layered structures.

The systems CoGa2S4CoV2S4 and CoGa2S4CoTi2S4 were studied by x-ray diffraction methods on quenched powder samples. In both systems new quaternary compounds CoGa1.8V0.2S4 and CoGa1.8Ti0.2S4 crystallizing in the trigonal layered structure of FeGa2S4 type (a=364.5, c=1203.8 pm and a=364.3, c=1205.8 pm, respectively.) have been obtained. They are formed only at temperatures above 800 and 900 °C, respectively, but can be quenched without decomposition. The phase width of both compounds increases with increasing temperature. For the end member compounds no phase width could be detected.

The crystal structure of CoGaInS4 has been determined from single crystal X-ray diffraction data and refined to R = 0.03. It crystallizes in the trigonal FeGa2S4 type (space group P 3 m1 , No. 164, a = 3.759(1), c = 12.184(2) A, Z = 1) with the following cation distribution: (Co0.61In0.39Ga)t(Co0.39In0.61)oS4. The system xCoGa2S4-(1 − x)CoIn2S4 is quasibinary. The compound CoGaInS4 has a large region of homogeneity with a marked dependence on temperature, ranging from x = 0.2 to x = 0.8 at 800°C. Compounds with high indium content show a phase transition to the ZnIn2S4(IIIa) type at 1000°C. Electronic spectra have been recorded on samples with different composition and on samples quenched from different temperatures.

An expedient synthesis of previously unknown (1 Z , 3 Z )-1, 4-dibromobutadiene is reported. When this dibromide is treated with s- or t-butyllithium, (1 Z , 3 Z )-1-bromo-4-lithio-butadiene is generated. Treatment of the dibromide with four equivalents of t-butyllithium gives (1 Z , 3 Z )-dilithiobutadiene. Reaction of (1 Z , 3 Z )-1-bromo-4-lithiobutadiene with (η 5 -C 5 H 5 )Fe(CO) 2 I gives (1 Z , 3 Z )-(η 5 -C 5 H 5 )Fe-(CO) 2 CH=CHCH=CHBr. X-ray crystallographic analysis of this latter compound establishes the geometry about the bromobutadiene ligand.

The specification generated during the requirements specification phase acts as a cornerstone for the entire software development process. The quality of this document directly influences the overall quality of the resulting software product. The process of requirements specification uses as its input a natural language requirements document, generated by the system's users. This document serves as a guide to the actual specification process. A method is presented for the evaluation and analysis of this document. This analysis permits improvements to be made in the initial requirements document before its use in a formalized specification paradigm. By improving the quality of this document, the input to the specification process is enhanced. This enhancement strengthens not only the developed specification, but also the entire software development process.