bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental questions about entropy III. A kind of mobile order in liquids : preferential contacts between molecular groups
Authors: Huyskens P. L. , Siegel G. G. 
Published: September 2010

AbstractAt 25°C, in liquid alcohols and in water an O‐H proton follows an oxygen atom of a neighbouring molecule in its peregrinations during a fraction (1‐γ) of the time (more than 95% for the lower alcohols). During this time the proton can be found only in a part Vo of the standardized domain <DomA> of the molecule. Neither Vo not <DomA> are fixed. The highly preferential contacts create in the liquid a kind of mobile order that does not exist in crystalline substances. As a consequence of the mobile order the standardized possibilities <WA> of one molecule A of the liquid are reduced by a factor <WA mobile order > = γ−γ (1‐γ)γ‐1 (Vo/ <DomA> 1‐γ. This factor is smaller than one. In the case of water there are two such factors, one for the first and the other for the second proton. The mobile order provokes a change in the molar entropy ΔSA mobile order = R In <WA mobile order> that is therefore negative. <DomA> is the volume of the solution divided by the number of A molecules. In the series of the normal alcohols, up to hexanol, the changes of γ can be neglected. Vo and the effects of H‐bonding on the vibrations can also be considered as constant. As a consequence in this series one expects an increase of the negative value of the entropy of mobile order according to d(−ΔSA mobile order) = R d ln VA. This is confirmed by the differences between the standard entropies of the alcohols and of their homomorphous hydrocarbons. In the vapour phase where H‐bonding is negligible, the differences are positive and practically constant: 13.8 ± 0.7 JK−1 mole−1. For the liquids the differences are negative and increase with the molecular weight.
Laterite as a catalyst for the hydrotreatment of heavy Oil. II. Influence of chemical and thermal treatments on the HDS and HDM activity
Authors: Yunes S. , Thakur D. S. , Grange P. , Delmon B. 
Published: September 2010

AbstractEffects of thermal treatment and iron extraction by the dithionate method (DCB) on the pore size distribution of laterite, and influence of iron and molybdenum impregnation on hydrodesulfurization (HDS) and hydrodemetallization (HDM) of natural DAO Morishal feedstock, were investigated. Thermal treatment up to 400°C noticeably improves pore size distribution and surface area. Higher temperatures drastically decrease the specific surface area, although the total pore volume remains constant. Iron extraction of laterite calcined at 550°C decreases HDS activity, but improves HDM activity. On the contrary, iron and molybdenum impregnation noticeably increases HDS activity and does not improve the HDM function.
A convenient preparation of 3H‐1,3‐Oxazol‐2‐One and its N‐formyl derivative
Authors: Tavernier Dirk , van Damme Sabine , Ricquier Patrick , Anteunis Marc J. O. 
Published: September 2010

AbstractThe electrochemical hydroxylation of 1,3‐oxazolidin‐2‐one to 4‐hydroxy‐1,3‐oxazolidin‐2‐one is reported; a substantial side product is the symmetrical ether derived from the hydroxycompound. An improved synthesis of 3H‐1,3‐oxazol‐2‐one has been developed; nothing more is involved than boiling the readily available 4‐methoxy‐1,3‐oxazolidin‐2‐one with an excess of acetic acid and one equivalent of acetic anhydride, evaporation of the solvents and recrystallization of the residue. The mechanism of the reaction is discussed. In a reinvestigation of the known conversion, by acetic anhydride, of 4‐methoxy‐1,3‐oxazolidin‐2‐one to N‐acetyl‐1,3‐oxazol‐2‐one, we have uncovered the formation of two 3,4′‐bioxazole side products [3‐(2‐oxo‐1,3‐oxazolidin‐4‐yl) 1,3‐oxazol‐2‐one and its N‐acetyl derivative], especially in the presence of added acids. We have found that N‐formyl‐1,3‐oxazol‐2‐one can be made in good yield by treatment of 3H‐1,3‐oxazol‐2‐one with a mixture of formic acid and acetic anhydride (“acetic formic anhydride”) in the presence of 4‐(N, N‐dimethylamino)pyridine; the formation of an intermediate phosphonate derived from 3H‐1,3‐oxazol‐2‐one, as described in the literature synthesis of N‐formyl‐1,3‐oxazolone, is superfluous.
Ft‐Ir study of the interaction between N, N,1,9‐tetramethylguanine and the Li+ Ion. Comparison with protonation
Authors: Parmentier J. , De Taeye J. , Zeegers‐Huyskens Th. 
Published: September 2010

AbstractThe interaction between N, N, 1, 9‐tetramethylguanine and the Li+ ion is investigated in acetonitrile and in the solid state by FT‐IR spectrophotometry. The spectroscopic results are in agreement with the ab initio calculations of Del Bene which predict a structure where Li+ is bonded to the N7 and O6 atoms. In contrast, protonation takes place on the N7 atom. The comparison of results for other carbonyl systems allows to establish a correlation between the calculated elongation of the carbonyl bond and the frequency variation of the °C = O vibration.
Nucleophilic substitutions on 2‐Chloro‐3‐Nitroquinoxaline
Authors: Nasielski‐Hinkens R. , Kaisin M. , Grandjean D. , Loos M. , Nasielski J. 
Published: September 2010

AbstractPiperidine, cyclohexylamine, methoxide ion and para‐thiocresolate ion react with 2‐chloro‐3‐nitroquinoxaline 1 by selectively substituting the nitro group, in contrast to the behavior of most ortho‐chloronitroaromatics which loose halide when subjected to nucleophilic substitution reactions. This inversion is interpreted as being due to the lack of activation of the 2‐position by the nitro group in the 3‐position because of the low value of the π‐bond index between these two vertices. It is also suggested that the substitution by neutral reagents such as amines is strongly influenced by stabilizing interactions between the negatively charged nitro group and the ammonium moiety in the σ complex; this built‐in solvation may be responsible for inversions in the chemoselectivity between chloro and nitro nucleofugicities.
Three new norditerpenes with an isopimarane skeleton from vellozia variabilis
Authors: Pinto Angelo C. , Ribeiro Núbia Moura , Brito Lavínia , Tinant Bernard , Declercq Jean Paul 
Published: September 2010

AbstractThree new γ‐lactone norditerpenes with an isopimarane skeleton were isolated from roots, stem and leaf sheaths of Vellozia variabilis. X‐ray diffraction analysis established the structure of one of these norditerpenes. The other two were elucidated through spectroscopic data and chemical correlation.
Electronic stabilized four‐membered tin cycles. Molecular structure of bis‐μ‐sulfido‐bis{1,4‐Diethyl‐1,4‐Diaza‐8‐Stannatricyclo [3. 2. 3.1,804,8]Undecane}
Authors: Schollmeyer D. , Kalbitz J. , Hartung H. , Tzschach A. , Jurkschat K. 
Published: September 2010

AbstractThe synthesis of the intramolecular penta and hexa‐coordinated tin compounds [MeN(CH2CH2CH2)2SnS]2 3, and [(CH2N(Et)CH2CH2CH2)2 SnS]2 5, is described and their 1H, 13C and 119Sn NMR data are reported. 5 crystallizes in the monoclinic space group P21/C with the unit cell dimensions a =8.977(2), b = 13.053(2), c = 13.310(1) Å, β = 103.54(2)ρ, V 1516.3(5) Å3, ρ= 1.529 g/cm3, Z=2. The structure was refined to a final R value of 0.058 for 1.774 observed independent reflections. The tin atoms are hexa‐coordinated by 2 C, 2 S and 2 N. The intramolecular Sn‐N distances amount to 2.766 and 2.859 Å.
Bicyclic imidazolidinones as potential antibiotics
Authors: Marchand‐Brynaert Jacqueline , Vanlierde Huguette , Ghosez Léon 
Published: September 2010

AbstractThe bicyclic imidazolidinones 5 topologically related to the penicillin family, are susceptible to form a stable carbamate with serine‐ D, D‐peptidases. A series of N‐7 acylated or sulfonylated (2R, 5R)‐ 3,3‐dimethyl‐8‐oxo‐4‐thia‐7, 1‐diazabicyclo[3.3.0]octane‐2‐carboxylates 12–21 have been prepared. None of these novel penicillin analogs exhibited antibacterial activity.
Electrochemical behaviour of the Ni(II) ion in soda‐lime‐silica melts
Authors: Claes P. , Tilquin J. Y. , Glibert J. 
Published: September 2010

AbstractDetermination of the oxidation state of solutes in glass‐forming melts can be made in situ using electrochemical techniques. Nevertheless accurate voltammetric measurements are perturbed by the simultaneous influence of broader voltamperometric signals and high residual currents. The aim of this investigation was to test various voltammetric methods as well as chronopotentiometry, chronoamperometry and AC impedance plots in order to analyze the electrochemical behavior of a given solute. The Ni(II) entity was selected, its reduction wave being well‐defined. Experiments were carried out over the temperature range from 1148 to 1473 K.
Spectroscopic and Thermodynamic Investigation of Molecular Complexes of 1,2,3,4‐Tetrachloro‐Bicyclo [4,2,0] Octa‐1,3,5‐Triene‐7,8‐Dione with π‐Electron Donors In Solution
Authors: Nagy Ottó B. , Szpakowska Mariola , Hevesi Làszló , Nagy Jà nos B. 
Published: September 2010

AbstractThe title compound (Q) forms readily molecular complexes with various π‐donor molecules in 1,2‐dichloroethane solutions. It is shown that the intermolecular charge transfer occurs between the highest occupied molecular orbital of the donors (D) and two closely spaced unoccupied orbitals of the acceptor Q. The complexes are of composition 1:1. They are rather weak having only slightly ionic intermolecular bonds. The studied complexes obey all the relationships valid for weak molecular complexes from which the unknown electron affinities of Q(EA1=0.916 eV and EA2=0.724 eV) and ionization potential of fluorene (ID=7.82 eV) could be determined. The LCDA MO theory is also fully borne out by the experimental data. It turns out that the new acceptor compares favourably with analogous halogenated oxygen containing π‐electron acceptors.
Monitoring of Deprotection Reactions of Cyclic Somatostatin Analogues by Fast Atom Bombardment Mass Spectrometry
Authors: Elseviers M. , Jaspers H. , Laus G. , Tourwé D. , van Binst G. 
Published: September 2010

AbstractThe removal of t‐butyloxycarbonyl‐, benzyloxycarbonyl‐and O‐benzyl group from protected somatostatin analogues by hydrogenolysis and acidolysis was monitored by FAB‐mass spectrometry. Sideproducts can be identified and the optimum deprotection conditions can be determined using a minimal amount of peptide.
Application De La Methodologie De La Recherche Experimentale A La Synthese Du Methylene‐2 Vinylcyclopentane Par Cyclodimerisation Du Butadiene A L'Aide De Complexes Du Nickel
Authors: Masotti Henriette , Peiffer Gilbert , Siv Chhan , Joblet Elisabeth , Luu Roger Phan Tan 
Published: September 2010

AbstractThe cyclodimerisation reaction of butadiene leading to methylene‐2‐vinylcyclopentane catalysed by zerovalentnickel in presence of Threophos ligand has been optimised using the experimental research methodology. Thus, we obtain the cyclodimer with 70% of selectivity for a conversion rate of 90% and this in the following conditions: temperature 80°C; time 6 hours; [ligand]/[Ni0]=1; [butadiene]/[Ni0]=80; [methanol]/[Ni0]=50.
Thermal Reactions of Arylamidoximes
Authors: Da Costa Leite Lúcia F. C. , Srivastava Rajendra M. , Cavalcanti Alexandre P. 
Published: September 2010

AbstractThe effect of heat on arylamidoximes, la‐g, has been examined. When acetic acid was used as solvent, amidoximes, la‐g, provided three products, viz., 3,5‐bis‐aryl‐1,2,4‐oxadiazoles, 2a‐g, 3‐aryl‐5‐methyl‐1,2,4‐oxadiazoles, 3a‐g, and a small quantity of an unknown polar compound. Heating arylamidoximes at controlled temperature without acetic acid furnished bis‐aryloxadiazoles, 2a‐g. An insight has been obtained about the mechanism of formation of 2 from 1.
Face Selectivity of the Diels‐Alder Reaction of Thebaine‐Like Morphinandienes, A Computational Approach (Chemistry of Opium Alkaloids, Part XXXI)
Authors: Linders J. T. M. , Maat L. 
Published: September 2010

AbstractMolecular mechanics {MMP2(85)} have been employed for the calculation of the geometry of morphinan‐6,8‐dienes.The X‐ray structure of desoxycodeine‐A, a morphinan‐5,7‐diene, and of other morphinans were well‐reproduced by the minimization program. The conformations of 4,5α‐epoxymorphinan‐6,8‐dienes and their 4‐hydroxy analogues show considerable differences, which account for the observed face selectivity in the Diels‐Alder cycloaddition.
Effect of the Anionic Ligand on the Equilibrium Between Mononuclear and Binuclear Complexes of Copper(II) Carboxylates in Pyridine‐Chlorobenzene Solutions
Authors: Szpakowska M. , Radecka Ł. 
Published: September 2010

AbstractThe electronic and EPR spectra of Cu(RCO2)2 [R=(CH3)2CH‐, C2H5‐, (CH3)3C‐] have been measured in pyridine‐chlorobenzene solvent mixtures. The results have been interpreted in terms of equilibrium between mononuclear and binuclear forms of copper(II) carboxylate complexes with pyridine. The dimerization constant, Kc, and ϵb ϵm values for bi‐ and mononuclear complexes have been determined in various mixed solvent compositions. The Kc values decrease with the basicity of the carboxylate ligand. The observed tendency is opposite to that obtained for Cu(II) carboxylate complexes with α‐methyl‐substituted pyridines. The axial position of pyridine ligands in the elongated octahedron structure of mononuclear forms seems to be responsible for this correlation. It appears also that detailed comparison of physico‐chemical properties of different copper complexes is possible only when the geometric structures of the species in equilibrium are identical. Furthermore, steric effect dominates the behaviour of complexes studied in binary solvent mixtures.
Acid Catalyzed Heterolysis of a Pyrazol α‐Chloroacetanilide Derivative with Alkyl‐Amidonitrogen Fission
Authors: Rouchaud Jean , Metsue Marc , Gustin Fabrice , Moulart Claude , Herin Marc 
Published: September 2010

AbstractThe base‐catalyzed hydrolysis of 2‐chloro‐N‐(2,6‐dimethylphenyl)‐N‐(1H‐pyrazol‐1‐ylmethyl)‐acetamide (1) generated 2‐hydroxy‐N‐(2,6‐dimethylphenyl)‐N‐(1H‐pyrazol‐1‐ylmethyl)‐acetamide (2). The acid‐catalyzed hydrolysis of compound 1 generated after a short time 2‐chloro‐N‐(2,6‐dimethyl)‐acetamide (3) and pyrazol (5); after a longer period of time, 4,4′‐methylenebis‐(2,6‐dimethylbenzenamine) (4) and pyrazol (5) were formed; compound 4 was formed by condensation of the non isolated intermediates 2,6‐dimethylaniline and formaldehyde. Thus the base‐catalyzed hydrolysis of compound 1 did not cleave the amide; the acid‐catalyzed one first cleaved the N‐amido‐alkyl bond; then, the N‐amido‐acyl bond, the hydrolysis products condensing simultaneously together to give the unexpected compound 4.
Exchange Reactions of Substituted Benzaldehyde Hydrazones
Authors: Hearn Michael J. , Sy Karen Grace 
Published: September 2010

AbstractHydrazones IV, derived from substituted benzaldehydes and N‐aminophthalimide, experience an exchange reaction with one equivalent of 2,4‐dinitrophenylhydrazine under conditions free of added mineral acid to cleanly and irreversibly produce the related 2,4‐dinitrophenylhydrazones V in good yields. Although literature melting points for compounds V may vary from one reference to another, the infrared spectra (v (mull), cm−1; IV: 1770, 1710; V: 3280, 1615, 1580, 1510) of starting materials and products in the exchange process are strikingly different and permit ready characterization.
Cyclization of A Linear Precursor of Virginiamycin S1 (VS1) Mediated by Woodward's Reagent K
Authors: Sharma N. K. , Anteunis M. J. O. 
Published: September 2010

AbstractCyclization of a model linear hexapeptide (VS1 linear peptide, 1) was achieved by using N‐ethyl‐5‐phenylisoxazolium‐3′‐Sulfonate (Woodward's Reagent K). Yields of the resulting cyclic product 2 were quite low (∼ 15%) in various solvents. The yield in CH2Cl2 increased substantially when the reaction was carried out under free air instead of N2 atmosphere.
Synthèse De Dérivés Oxo De La Benzoselenazine‐1,3
Authors: Mbuyi M. , Christiaens L. , Renson M. 
Published: September 2010

AbstractSynthesis of 1,3‐benzoselenazine derivatives is attempted via cyclization of o‐methylselenobenzoylformamidines, via ring‐expansion of 1,2‐benzisoselenazolin‐3‐ones and via N‐ethoxy‐carbonyl o‐bromoselenobenzaldimine. This research succeeded in the synthesis of 2,3‐dihydro‐4H‐1,3‐benzoselenazine‐2,4‐dione and 2,3‐dihydro‐4H‐1,3‐benzoselenazine‐4‐one.
Étude De La Réactivité Du Bis‐[Phényl‐4 Oxo‐2 Benzodiazépine‐1,5 YL‐1]‐1,1' Méthane
Authors: Achour Reddouane , Essassi El Mokhtar , Salem Moussa , Zniber Rachid 
Published: September 2010

AbstractStudy of the reactivity of Bis‐1,1'‐[4‐phenyl 2‐oxo 1,5‐benzodiazepine 1‐yl]methane allowed us to throw into relief different reactive site of this type of molecule.
TG/XRD/Sem Study of the Conversion of Gibbsite to (Pseudo) Boehmite
Authors: Decleer Jos G.M. 
Published: September 2010

AbstractThe conversion of gibbsite to (pseudo) boehmite has been studied by thermogravimetry, X‐ray diffractometry and scanning electron microscopy, supplemented by density and surface area measurements. As a reference for desired product properties, commercial pseudoboehmite, laboratory synthesized pseudoboehmite and autoclaved boehmite have also been studied. Three kinds of heating processes have been applied: in an oven, in a steam flow and under vacuum. All experiments were carried out at 220°C. Prolonged heating under vacuum resulted in a complete conversion of gibbsite to (pseudo) boehmite. The product still differs too much from commercial pseudoboehmite to be a valuable alternative. Also taking into account the manufacturing implications of vacuum heating, this process seems hardly feasible on a large scale.
Synthesis and Study of Rh(III), Pd(II), Pt(II), Ag(I) and Au(III) Complexes of 1‐Methyl‐3, 4‐Diphenylpyrazole
Authors: Kovala‐Demertzi Dimitra , Perlepes Spiros P. , Lazaras George 
Published: September 2010

AbstractThe new complexes [RhLCl3]x, mer‐[RhL3Cl3], (LH)2[MCl4] (M=Pd,Pt), cis‐[ML2Cl2] (M=Pd,Pt) trans‐[PdL2Cl2], [AgL2](NO3), (LH)[AuCl4] and [AuLCl3], where L=1‐methyl‐3, 4‐diphenylpyrazole, have been isolated. Several synthetic routes were investigated. The complexes were characterized by elemental analyses, conductivity measurements, X‐ray powder patterns, thermal methods, magnetic susceptibilities and spectral (IR and far‐IR, Raman, ligand field, 1 H‐NMR) studies. Pseudooctahedral stereochemistries for the Rh(III) complexes and square planar structures for the Pd(II), Pt(II) and Au(III) compounds are assigned in the solid state. The Ag(I) complex exhibits a linear twofold coordination with [AgL2]+ cations and uncoordinated nitrates. The unsubstituted N(2) atom (the “pyridine” nitrogen) of L is the donor atom to the metal ions or the protonation site.
Influence of Several Factors on the Determination of Manganese Using Electrothermal Atomic Absorption Spectrometry
Authors: Stobbaerts R. F. J. , Deelstra H. A. 
Published: September 2010

AbstractThe influence of instrumental parameters on the determination of Mn using EAAS is investigated and the interference of several acids, cations and anions determined. When NaCl or KCl is present an interference suppressor, such as L‐ascorbic acid, has to be added. The contamination resulting from dust particles in the laboratory or from a mixer is found to be negligible. Using NBS samples several destruction techniques are investigated and comparison is made with results obtained by FAAS.
Polyimides: Synthèse, Caractérisation Et Applications
Authors: Grenier‐Loustalot Marie‐Florence 
Published: September 2010

Abstract13C high resolution liquid and solid (CP MAS) states NMR spectroscopy has been coupled with DSC, Xray diffraction, infrared Fourier transform spectroscopy techniques to study the mechanisms, kinetics, solid state structures and conformation of several polyimides.Chemical data were obtained on model compounds and applied for polymers synthetised by polycondensation or chain extension and crosslinking.We have shown that solid state 13C NMR and IRFT were able to detect chemical structure differences caused by different cure schedules.
Poly(p‐Thiophénylene) Et Ses Copolymères Synthèses Et Mécanismes Réactionnels
Authors: Fradet Alain 
Published: September 2010

AbstractPoly(p‐thiophenylene (PPS) can be synthesized following some very different reaction paths: electrophilic substitution, nucleophilic substitution or electrooxidation. The most popular route involves high temperature nucleophilic substitution of 1,4‐dihalo benzene by sodium sulfide in dipolar aprotic solvents like NMP. The mechanism of this reaction has not yet been clearly established. Several mechanisms have been put forward: SNAr and single electron transfer chain processes with the formation of either radical cations or radical anions as reactive intermediates. They are reviewed and discussed. To obtain more information on the mechanism, the reactivity of halogen in ZϕX with X=halogen has been investigated. Depending on the nature of Z, large differences of reactivity were found and are discussed in relation to the proposed mechanisms.
Les Polysiloxanes: Développements Récents
Authors: Leempoel Patrick , Parbhoo Bhukan 
Published: September 2010

AbstractPolysiloxanes are characterized by an inorganic backbone made from siloxy units, substituted by hydrocarbon groups. They can be classified in cyclic, branched and linear polymers. The latter constitute the most important class and are extensively used due to the numerous substitution options of the hydrocarbon chains by terminal or pendant organic groups, functional or not. The presence of such groups opens up all the doors of organic chemistry and these new molecules are used in many different area such as High Technology or for the synthesis of silicone‐organic copolymers.
Synthesis and Characterization of New Macrocyclic Imine‐Carbinolamine Complexes of Nickel(II)
Authors: Amer S. A. , El‐Hefnawy G. B. , Seleim G. W. , Desseyn H. O. 
Published: September 2010

AbstractReaction of 2,3‐diformylfurane and ethylenediamine in ethanol in the presence of nickel(II) acetate gives an imine‐carbinolamine macrocyclic complex whilst its reaction with propylenediamine gives a diimine macrocyclic complex. The imine‐carbinolamine macrocyclic complex can also be prepared by reaction of 2,3‐diformylthiophene and ethylenediamine in ethanol in the presence of nickel(II) acetate. Attempts to prepare macrocyclic compounds of 2,3‐diformylthiophene and propylenediamine were unsuccessful. On the basis of various physical properties, the complexes can be described as four coordinate, square planar structures for imine‐carbinolamine macrocyclic complexes and six co‐ordinate, pseudo‐octahedral structure for the diimine. Simple reactions led to the isolation of isothiocyanate and perchlorate derivatives including neutral complexes having axially coordinated isothiocyanate and perchlorate.
Synthesis, Physical Properties and Spectroscopy of Pd(II) Complexes With CH3OOCCSNH2
Authors: Jacobs Patrick , Dimitrou Katerina , Perlepes Spiros P. , Plakatouras John , Desseyn Herman O. 
Published: September 2010

AbstractThe new complexes trans‐[Pd(HL)2Cl2] 0.5 H2O, trans‐[Pd(HL)2X2] (X=Br, I, SCN). [Pd(HL)(ONO2)2]. cis‐[Pd(HL2)X2] (X=NCS, ONO2) and [Pd(HL)4]X2 (X=Cl, ClO4), where HL=H2NCSC′OOCH3, have been prepared. The complex trans‐[Pt(HL)2Cl2] was also isolated for comparison reasons. The complexes were characterized by elemental analyses, conductivity measurements, X‐ray powder patterns, TG/DTG studies and spectral (1H‐NMR electronic, IR and far‐IR, Raman) studies. The vibrational analysis of the complexes is also given using deuterium isotopic substitutions. Monomeric square planar structures are assigned for the 1:2 and 1:4 complexes in the solid state: the 1:1 nitrato complex is a polymer containing both monodentate and bidentate bridging nitrato groups. The thioamide sulfur atom of HL is the donor atom to Pd(II) and Pt(II). The thiocyanate ions are coordinated through sulfur in the trans complex and through nitrogen in the cis product. This differentiation in the mode of thiocyanate bonding is discussed.