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A series of acylsulfenyl iodides (RCOSI) were synthesized by the reactions of carbothioic acid group 11–16 element derivatives with iodine or N-iodosuccinimides in moderate to good yields.

This paper aims to clarify the effect of kaolin on the ash partitioning during combustion of a low-rank coal in O2/CO2 atmosphere. The coal sample was mixed mechanically with 10% kaolin and then combusted in a lab-scale drop tube furnace at 1400 °C in oxy-fuel atmosphere (28% O2 balanced with CO2). The resulting ash was segregated as bottom ash, fine ash and ultrafine ash. The ash distribution as a function of the particle size of kaolin added was examined. The results indicated that the particle size range of kaolin with 106–150 µm was the optimal for shifting the fine/ultrafine ash to the bottom ash, in which the total amount of fine and ultrafine ash was decreased by 18.1% compared with that of the raw coal combustion. The ultrafine ash with particle size less than 0.5 µm generated from combustion of the coal mixed with kaolin (106–150 µm) was decreased remarkably since alkali and alkaline earth metals (AAEM) including Na, K, Ca and Mg were captured by kaolin at high temperature. The formation of liquid layer on the surface of kaolin and coalescence of AAEM-rich particles were the main reason for shifting the fine/ultrafine ash to the bottom ash.

A series of Group 2 metal bis(arenecarbochalcogenoato)(crown ether) complexes M(EE'CAr)2(L)(L')x (M = Mg, Ca, Sr, Ba; Ar = aryl; E = S, Se; E' = O, S; L = H2O or THF; L' = 15-crown-5, 18-crown-6) were synthesized and their structures were revealed by X-ray analyses. The two carbothioato ligands in Mg, Ca and Sr 15-crown-5 complexes are located on the same side of the crown ether plane, while those in Mg, Ca, Sr, and Ba 18-crown-6 compounds are on both sides of the 18-crown-6 plane (trans relative to the plane). For the Ca 15-crown-5 complex, both carbothioato ligands are connected to the central Ca ion through an oxygen atom in a monodentate manner, and the two hydrogen atoms of the coordinated water molecule are intramolecularly hydrogen-bonded with thiocarbonyl sulfur atoms. One of the two carbothioate groups in the Ca 18-crown-6 complex is connected in a bidentate manner to the central metal, while the other is connected in a monodentate manner through an oxygen atom. The two thiocarboxylato ligands in the Sr 15-crown-5 congener are connected in a bidentate fashion to the same side of the crown ether plane. The Ca and Sr compounds are the first examples of alkali earth metal carbochalcogenoate complexes in which carbochalcogenolato ligands are connected in a monodentate manner through an oxygen atom. Both chalcogenoato ligands in Ba(SOCC6H4Me-4)2(18-crown-6) and Sr(SeOCC6H4Me-4)2(18-crown-6) are coordinated in a bidentate manner to the central metal ion.

The first ferrocenecarboselenoic acid was synthesized and characterized. The existence of tautomeric equilibrium between the selenol (FcCOSeH) and selenoxo forms (FcCSeOH) in polar solvents was proven by 1H-, 13C- and 77Se-NMR spectra. The selenoxo form exists predominantly in a polar solvent at low temperature below –70 °C. Treatment of this acid with lithium, sodium, and potassium hydrides and with rubidium and cesium fluorides gave the corresponding alkali metal ferrocenecarboselenoates in quantitative yields. Treatment with 4-methylphenyl isocyanate at room temperature led to ferrocenoyl 4-methylphenylcarbamoyl selenide FcCOSeC(O)NHC6H4Me-4 in high yield. A similar reaction with phenyl isothiocyanate formed a mixture of FcCOSeC(S)NHPh and FcCOSeC(SH)=NPh in moderate to good yield. The carboselenoic acid readily reacted with piperidine to give piperidinium ferrocenecarboselenoate in good yield. Air oxidation of this selenoic acid afforded diferrocenoyl selenide as a major product along with diferrocenoyl diselenide. The structures of the selenide (FcCO)2Se and diselenide (FcCOSe)2 were examined by single-crystal X-ray analysis.

Lithium, sodium, and potassium ferrocenecarboselenoates were synthesized in good yields by the reaction of ferrocenoyl chloride with the corresponding metal selenides. In air, the saltsquickly oxidized to give diferrocenoyl diselenide. The salts readily reacted with alkyl and organo-germanium, -tin and -lead halides to give the corresponding Se-alkyl and Se-organo Group-14 element ferrocenecarboselenoates [(FcCOSe)xMPh4–x (M = Ge, Sn, Pb; x = 1–3) in moderate to good yields. In contrast, the reaction of the sodium and potassium salts with trimethylsilyl chloride led to O-trimethylsilyl ferrocenecarboselenoate FcCSeOSiMe3. Treatment of the O-silyl ester with RbF and CsF led to rubidium and cesium ferrocenecarboselenoates, respectively, in good yields. The structures of FcCOSetBu, (FcCOSe)2SnPh2, and FcCOSePbPh3 were revealed by X-ray molecular structure analysis.

Compound (2-MeOC6H4CS)2S (1) showed an unusual saddle structure in which the –C(=S)–S–C(=S)– moiety is planar and two benzene rings lie a face-to-face and the distances (3.07 A) between the central sulfur atom and two 2-methoxy oxygen atoms are within the sum of van der Waals radii of the both atoms. However, the results of MO calculation at the B3LYP/6-311+G(2d, p) level showed no orbital interaction between both atoms. From the results of the calculations at the MP2 level, it was deduced that the crystal packing effect is important for such densely packed crystal, due to its less effective volume. On the other hand, the para-methoxy derivative (4-MeOC6H4CS)2S (2) in which the two methoxy oxygen atoms are not able to contact with the central sulfur atom shows an L-shaped structure in which the –C(=S)–S–C(=S)– moiety is not planar. The –C(=O)–S–C(=S)– moiety in compound (2-MeOC6H4CO)(2-MeOC6H4CS)S (3b) shows an L-shaped structure, though the two methoxy oxygen atoms are in intramolecular contact with the central sulfur atom. The deep blue to green colors of compounds 1 and 2 and the deep violet color of compound 3b are due to transitions of the lone-pair electrons in the HOMO (ψ87) of the thiocarbonyl sulfur atom to the LUMO (ψ89)and of those in the HOMO (ψ83) of the thiocarbonyl sulfur atom to the LUMO (ψ85), respectively.

A series of Te-1-acylmethyl carbotelluroates was prepared in good isolated yields from the reaction of potassium carbotelluroates with α-haloketones in acetonitrile. Thermolysis of the telluroesters afforded vinyl esters in 20−50% yields, while treatment of the carbotellurorates with potassium t-butanolate led to 1,3-diketones in 30−75% yields with the liberation of black tellurium. The reaction of potassium carbotelluroates with α-haloaceto oximes gave O-acyl oximes in 50−70% yields via Te-1-iminomethylcarbotelluroates.

The cathodic reduction of selenonium salts bearing substituted benzyl, allyl and ethoxycarbonylmethyl group gave the ylides which were confirmed by the Corey-Chaykovsky reaction with benzaldehyde. In the absence of benzaldehyde, the [2,3] Sigmatropic rearrangement, coupling reaction, and olefin or cyclopropane formation via the ylides occurred in good yield. To elucidate the reaction mechanisms of the reactions of selenium ylides from selenium salts bearing allyl group, the theoretical density functional calculations were performed by using B3LYP with the 6–31+G(d) basis set.

A wide range of selenium-containing reagents are known to undergo addition – elimination reactions under different reaction conditions. We report on selenium electrophiles, which are regenerated under the reaction conditions employed, and therefore only catalytic amounts of these reagents are necessary.

The generation and use of selenium electrophiles in ­catalytic, electrochemically driven selenenylation-elimination sequences is described.

Bowl-shaped phosphine (BSP) ligands markedly accelerated the rhodium-catalyzed hydrosilylation of ketones and ketimines as compared with the effect of conventional phosphine ligands such as PPh3 an...

Reaction of 2-(aminomethyl)pyridine with selenium dioxide leads to the formation of imidazo[1,5-a]pyridine (2-azaindolizine) skeleton in a single step. The major products of the reactions are 3-(2-...

This chapter has reviewed two types of rearrangements of compounds involving seleno- and tellurocarbonyl groups. First, focus has been laid on the rearrangement of a proton, that is tautomerization. Several types of tautomerizations such as selone/selenol and tellone/tellurol (keto/enol type isomerization), chalcogenocarboxylic acids (selenol/selenoxo and tellurol/telluroxo isomerization), and selenoamidate/selenoimidate and telluroamidate/telluroimidate are described. The seleno- and tellurocarbonyl groups have generally been understood to be less stable than the corresponding carbonyl and thiocarbonyl groups. Nevertheless, in many cases, chalcogenoxo forms are readily generated. Intramolecular and intermolecular hydrogen bonds also play crucial roles in these tautomerizations. Several theoretical approaches to the tautomerizations are also introduced. Many of them are in accordance with experimental results. Second, selenium and tellurium versions of Claisen rearrangements are discussed. Seleno- and telluro- Claisen rearrangements generally precede milder than ordinary rearrangement and the sulfur version. In the rearrangement generating seleno- and telluoraldehdyes, these reactive species are trapped with dienes and alkenes. The availability of the rearrangement involving selenoamides and selenotihoic acid S-esters as synthetic tools has been shown, in particular, for the construction of quaternary carbon centers. Despite these experimental developments, theoretical studies on seleno- and telluro-Claisen rearrangement have yet to be achieved. Keywords: tautomerization; tautomeric rearrangements; seleno-Claisen rearrangement; telluro-Claisen rearrangement; selenocarbonyl compounds; tellurocarbonyl compounds; rearrangement; isomerization

Bis(phosphine)bis(tellurocarboxylato)-palladium(II) and -platinum(II), [M(RCOTe)2(PR′3)2] (M = Pd or Pt; R = But, Ph, 4-MeC6H4, etc.; R′ = Et or Ph), were synthesized in moderate to good yields by treating sodium tellurocarboxylates or O-trimethylsilyl telluroesters with [MCl2(PR′3)2]. The platinum complexes with 2-methoxybenzenecarbotelluroato ligands also were synthesized from [Pt(PR′3)4] with the corresponding diacyl ditelluride. The tellurocarboxylato complexes are yellow to orange or red crystals, and labile thermally and toward oxygen. The nickel analogues [Ni(RCOTe)2(PR′3)2] (R′ = Et or Ph) were obtained by similar fashion, but were too labile to isolate. X-Ray diffraction analysis of trans-[Pt(4-MeC6H4COTe)2(PEt3)2] was carried out, and compared with those of the corresponding thio- and seleno-carboxylato complexes. These complexes crystallized in the same space group (P21/c) and are isostructural having a square-planar co-ordination geometry with thio- or telluro-carboxylato ligands which are unidentate.

Thiocarboxylic acids, such as selenocarboxylic acids, exist predominantly in the thioxo form (RCSOH, thion acid) in polar solvents such as tetrahydrofuran (THF) at temperatures below −50 °C. Tellurocarboxylic acids (5) were observed for the first time by acidolysis of the corresponding cesium tellurocarboxylates with hydrogen chloride. The telluroic acids (6) exist predominantly in the telluroxo form (RCTeOH, telluron acid) in THF at temperatures below −70 °C. Telluron acids were reddish to blue violet for the aliphatics (R = alkyl) and dark green for the aromatics (R = aryl) and reacted with aryl isocyanates at −70 °C to give crystalline acyl carbamoyl tellurides in good yields.

The X-ray structure analysis of arenecarbochalcogenoic acids (ArCOEH and ArCEOH, E = S, Se, Te) is successful for 4-MeC6H4COSH for the first time, which reveals that the syn-conformer forms a plana...

[2455-14-3] C28H40O2 (MW 408.63) InChI = 1S/C28H40O2/c1-25(2,3)19-13-17(14-20(23(19)29)26(4,5)6)18-15-21(27(7,8)9)24(30)22(16-18)28(10,11)12/h13-16H,1-12H3 InChIKey = GQIGHOCYKUBBOE-UHFFFAOYSA-N (oxidizing reagent for various oxidation reactions such as oxidative coupling of organometallic compounds, oxidative cross-coupling between nitrones and alkynes, N-heterocyclic carbene-catalyzed oxidative esterification, amidation, and azidation of aldehydes, Michael addition to α,β-unsaturated aldehydes) Alternate Names: 3,3′,5,5′-tetra-tert-butyl-4,4′-dibenzoquinone; 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone; 2,6-bis(1,1-dimethylethyl)-4-[3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadien-1-ylidene]-2,5-cyclohexadien-1-one; 2,6-bis(1,1-dimethylethyl)-4-[3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexa-dien-1-ylidene]-2,5-cyclohexadien-1-one; 2,2′,6,6′-tetra-tert-butyldiphenylquinone. Physical Data: mp 246 °C,1 244−246 °C.2 Solubility: sol MeOH, EtOH, iPrOH, THF, acetone, AcOH, hexane; insoluble in water. Form Supplied in: commercially available as a red to purple solid. Preparative Method: synthesized by oxidation of 2,6-di-tert-butylphenol with oxygen gas in the presence of KOH in t-BuOH.1 Purification: recrystallization from EtOH.1 Handling, Storage, and Precautions: store away from oxidizing agents in dark and cool place in tightly sealed container; avoid inhalation and contact with skin and eyes.

Reaction of 2-(aminomethyl)pyridine with selenium dioxide leads to the formation of imidazo[1,5-a]pyridine (2-azaindolizine) skeleton in a single step. The major products of the reactions are 3-(2-...

Thiocarboxylic acids, such as selenocarboxylic acids, exist predominantly in the thioxo form (RCSOH, thion acid) in polar solvents such as tetrahydrofuran (THF) at temperatures below −50 °C. Tellurocarboxylic acids (5) were observed for the first time by acidolysis of the corresponding cesium tellurocarboxylates with hydrogen chloride. The telluroic acids (6) exist predominantly in the telluroxo form (RCTeOH, telluron acid) in THF at temperatures below −70 °C. Telluron acids were reddish to blue violet for the aliphatics (R = alkyl) and dark green for the aromatics (R = aryl) and reacted with aryl isocyanates at −70 °C to give crystalline acyl carbamoyl tellurides in good yields.

Several potassium selenocarboxylates were synthesized in moderate to good yields by the direct reaction of acyl chlorides with potassium selenide. The potassium salts were readily oxidized with XeF2 to give diacyl diselenides in quantitative yields. The structure of di(4-methoxybenzoyl) diselenide was established by X-ray diffraction analysis. Intramolecular interactions between the carbonyl oxygen and the selenium that is connected to the opposite carbonyl group were observed. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 373–379, 1999

The reaction of S-2-(trimethylsilyl)ethyl selenothioates with KF, CsF, and RbF gave the corresponding alkali metal selenothioates in moderate to good yields. The use of 18-crown-6 ether gave the products in higher yields. The molecular structure analyses of some of metal salts were carried out.

A series of aromatic diacyl tellurides were prepared in moderate to good yields by the reactions of sodium orpotassium arenecarbotelluroates with acyl chlorides in acetonitrile. X-ray structure analyses and theoretical calculations of 2-methoxybenzoic anhydride and bis(2-methoxybenzoyl) sulfide, selenide and telluride were carried out. The two 2-MeOC(6)H(4)CO moieties of bis(2-methoxybenzoyl) telluride are nearly planar and the two methoxy oxygen atoms intramolecularly coordinate to the central tellurium atom from both side of C(11)-Te(11)-C(22) plane. In contrast, the oxygen and sulfur isologues (2-MeOC(6)H(4)CO)(2)E (E = O, S), show that one of the two methoxy oxygen atoms contacts with the oxygen atom of the carbonyl group connected to the same benzene ring. The structure of di(2-methoxybenzoyl) selenide which was obtained by MO calculation resembles that of tellurium isologues rather than the corresponding oxygen and sulfur isologues. The reactions of di(aroyl) tellurides with Grignard reagents lead to the formation of tellurocarboxylato magnesium complexes [MgBr][R(C=Te)O].

A new and convenient one-pot method for a catalytic addition-elimination reaction using selenium electrophiles has been developed. In the presence of 5 mol % diphenyl diselenide, [bis(trifluoroacetoxy)iodo]benzene in acetonitrile converted a range of (E)-3-butenoic acids into the corresponding butenolides in good yields.

Since the nature of P ligands is very important in transitionmetal-catalyzed reactions, a wide variety of these ligands has been designed to realize high catalytic activity and selectivity.[1] So far, most P ligands are rather small, and their design and modification have hitherto been performed within close proximity of the P atom. Recently, several large (nanosized) phosphorus ligands were developed for transition-metalcatalyzed reactions.[2,3] In the course of our studies,[3] we found that a bowl-shaped[4] phosphane ligand markedly enhances the rate of rhodium-catalyzed hydrosilylation of ketones.[5] The two triarylphosphanes tris(2,2’’,6,6’’-tetramethyl-mterphenyl-5’-yl)phosphane[6] (denoted as P(tm-tp)3) and tris(m-terphenyl-5’-yl)phosphane (denoted as P(tp)3) were prepared and compared with common phosphanes in the rhodium-catalyzed hydrosilylation of cyclohexanone with a trisubstituted silane (Table 1). P(tm-tp)3 was first prepared in 2001[6a] and its Pd0 complex [Pd{P(tm-tp)3}2] was reported in 2002.[6b] In the presence of catalytic amounts of P(tm-tp)3 and [{RhCl(C2H4)2}2] (P/Rh= 2), the reaction proceeded smoothly in benzene at room temperature over 3 h, and cyclohexanol was obtained in 97% yield after desilylation (Table 1, entry 1). In contrast, the same reaction with P(tp)3 afforded the product in only 25% yield (entry 2). Furthermore, other representative triarylphosphanes (entries 3–6) and trialkylphosphanes (entries 7–9) were also much less effective than P(tm-tp)3. With these ligands (entries 2–9), the reactions were sluggish at room temperature, and much longer reaction times (40–500 h) were required to obtain the products in good yields (70–95%). A kinetic study indicated that the P(tm-tp)3 catalyst system (entry 1) realized 154, 31, and 28 times faster reactions than PPh3 (entry 3), P(tp)3 (entry 2), and P(o-tol)3 (entry 5), respectively.[7] Benzene is a better solvent than CH2Cl2 in the reactions of entries 1–3. The rate enhancement with P(tm-tp)3 was further confirmed with various silanes and ketones, and compared with P(tp)3 and PPh3 (Table 2). With HSiEt3 (Table 2, entries 1–3) or HSiMePh2 (entries 4–6), the hydrosilylation of cyclohexanone proceeded much faster with P(tm-tp)3 (entries 1 and 4) than with P(tp)3 (entries 2 and 5) and PPh3 (entries 3 and 6). Furthermore, in the hydrosilylation of various ketones such as acetophenone (entries 7–9), 2-octanone (entries 10–12), and ( )-menthone (entries 13–15), rate enhancement with P(tmtp)3 was also evident. As catalyst precursor, the cationic rhodium complex [Rh(cod)2]BF4 (cod= cyclooctadiene) showed a similar rate enhancement with P(tm-tp)3 (entries 16–18). P(tm-tp)3 is a much more efficient than P(tp)3, although the two ligands strongly resemble each other. The structures of P(tm-tp)3 and P(tp)3 were optimized by HF/6-31G(d) calculations[8a] on initial structures generated by CONP R

Potassium, rubidium, and cesium thiocarboxylates were found to be synthesized by the reaction of thiocarboxylic acid or its O-trimethylsilyl esters with KF, RbF, and CsF. Tetramethylammonium thiocarboxylates were prepared in good yields by the reaction of sodium thiocarboxylates with tetramethylammonium chloride. The structures of potassium benzene-, 2-methoxybenzene-, and 4-methoxybenzenecarbothioates, rubidium 2-methoxybenzenecarbothioate, tetramethylammonium 2-methoxy- and 2-trifluoromethylbenzenecarbothioates, potassium 2-methoxybenzenecarboselenoate, and rubidium 2-methoxybenzenecarbotelluroate were characterized by X-ray structural analysis. All of these alkali metal salts exhibit a dimeric structure in which the oxygen and/or sulfur atom is associated with the metal of the opposite molecule, while the tetramethylammonium thiocarboxylates are monomeric. In potassium 2-methoxybenzenecarbothioate, the two thiocarboxylate groups chelate to the potassium atoms above and below the plane which involves the thiocarboxylate groups. In potassium 4-methoxybenzenecarbothioate, one thiocarboxylate group chelates to potassium. Without exception, the o-methoxy oxygen intermolecularly coordinates to the metal of the opposite molecule. The C-O bond lengths of the thiocarboxylate group are in the range 1.22-1.24 A, which is slightly longer than those of common thioesters. The C(sp(2))-S distances are in the range 1.70-1.72 A, which is close to that of a typical C-S single bond and suggests that the negative charge may be somewhat localized on the sulfur atom. The interaction number of the metals with oxygen and sulfur atoms was 7 for K and 8 for both Rb and Cs. The dihedral angle between the thiocarboxyl group and the phenyl ring is substantially increased by the introduction of the o-methoxy group. In these alkali metal thio-, seleno-, and tellurocarboxylates, only cesium 2-methoxybenzenecarbotelluroate showed an intermolecular nonbonding interaction between the cesium and the phenyl ring carbons.

Dithiocarboxylic acids and their trimethylsilyl esters were found to readily react with potassium, rubidium, and cesium fluorides to give the corresponding alkali metal dithiocarboxylates 3-5 in moderate to good yields. A series of tetramethylammonium dithiocarboxylates 8 have been prepared in good yields by the reaction of sodium dithiocarboxylates 7 with tetramethylammonium chloride. The structures of potassium (3b), rubidium (4g), cesium (5f), and tetramethylammonium 4-methylbenzenecarbodithioates (8e) and tetramethylammonium 2-methoxybenzenecarbodithioate (8f) were characterized crystallographically. These heavier alkali metal salts (3b, 4g, 5f) have a dimeric structure [(RCSSM)(2), M = K, Rb, Cs] in which the two dithiocarboxylate groups are chelated to the metal cations which are located on the upper and lower sides of the plane involving the two opposing dithiocarboxylate groups. The K(+) cations interact with the tolyl fragment of a neighboring molecule, while the Rb(+) and Cs(+) cations interact with two neighboring tolyl fragments, in which the ipso and ortho carbons are positioned close to the metals. The interaction number of the metals with surrounding atoms is 8 for K(+) and Rb(+) and 12 for Cs(+). The C-S distances of the dithiocarboxylate group are different for the potassium salt 3b. In contrast, those of the rubidium salt 4g and cesium salt 5f are equal. Similarly, the chelating sulfur-metal bond distances of 3b are different, while those of 4g and 5f are almost equal. The dihedral angles of the phenyl ring and dithiocarboxylate plane increase in the order of the K, Rb, and Cs salts. The structural analysis of sodium 4-methylbenzenecarbodithioate (7g) revealed the presence of 4-CH(3)C(6)H(4)CS(2)Na(0.36). In contrast, the tetramethylammonium salts 8 are monomeric where the cation moieties are located out of the dithiocarboxylate plane. The potassium 3, rubidium 4, and cesium dithiocarboxylates 5 readily reacted with methyl iodide or triorganotin chlorides at room temperature to give the corresponding methyl 9 and triorganotin dithioesters 10 in good yields. At 0 degrees C, the reactivity of the rubidium 4 and cesium salts 5 to methyl iodides decreases dramatically compared with those of the sodium salts 7 and potassium salts 3.

The first synthesis and characterization of sodium and potassium tellurocarboxylates were achieved by the reaction of acyl chlorides with the corresponding alkali metal tellurides. The salts are yellow to red solids or oils. The aliphatic derivatives are very sensitive toward oxygen and very thermally sensitive. However, the aromatic derivatives are relatively stable and can be stored for 1 week below -5 degrees C and under oxygen-free conditions. The most practical method for the synthesis of Te-alkyl telluroesters was established by the reaction of the sodium and potassium tellurocarboxylates with alkyl iodides at 0 degrees C. The first X-ray structural analysis of telluroesters (RCOTeR') was carried out for Te-methyl 4-chlorobenzenecarbotelluroate (4-ClC(6)H(4)COTeCH(3)), whose crystals are monoclinic (P2(1)/a) with a = 5.975(3) A, b = 14.517(2) A, c = 10.617(3) A, beta = 92.74(3) degrees, V = 919.8(4) A(3), and Z = 4. The molecule was nearly planar. The C=O and C-Te bond lengths are 1.204(3) and 2.153(3) A, respectively, indicating C=O double and C-Te single bonds. The C-Te-C angle of the C(O)TeCH(3) moiety is close to a right angle (92.3 degrees ), much more narrow compared with those [C-E-C, E = O (>105 degrees ), S (>102 degrees ), Se (>95)] of common esters and thio- and selenoesters (ArC(O)ER', E = O, S, Se; R' = alkyl). The nu(C=O) bands and the (13)C=O and (125)Te NMR spectra of the sodium and potassium tellurocarboxylates are discussed in comparison with those of other alkali metal or oxygen, sulfur, and selenium isologues.

A series of selenium and tellurium bis(carbodithioates and carbothioates) were synthesized. X-Ray structure analysis revealed that Se(SSCC(6)H(4)OMe-2)(2), Te(SSCC(6)H(4)OMe-2)(2) and Te(SSCC(6)H(4)Me-4)(2) have trapezoidal-planar configuration of ES(4) (E = Se, Te) and despite the larger atomic radii, the C=S···Te distances in Te(SSCC(6)H(4)OMe-2)(2) are comparable to those in the corresponding selenium derivatives Se(SSCC(6)H(4)OMe-2)(2). Molecular-orbital calculations performed on compounds E(E'SCR)(2) (E = S, Se, Te; E' = O, S; R = Me, Ph, C(6)H(4)OMe-2) showed that the syn-conformers of Se(SSCR)(2) and Te(SSCR)(2) are more stable than the corresponding anti-ones, while, in the case of carbothioic acid derivatives, E(SOCR)(2) showed that their anti-conformers are all more stable than the corresponding syn-ones. Natural bond orbital (NBO) analyses of these dithio-compounds revealed that two types of orbital interactions, n(S(1))→σ*(E-S(2)) and n(O)→σ*(E-S(2)), play a role in the bonding of E[S(2)S(1)CC(6)H(4)OMe-2](2) (E = Se, Te) and the former play a particularly predominant role.

The reaction of S-2-(trimethylsilyl)ethyl selenothioates with KF, CsF, and RbF gave the corresponding alkali metal selenothioates in moderate to good yields. The use of 18-crown-6 ether gave the products in higher yields. The molecular structure analyses of some of metal salts were carried out.

l-Cyano-3-(2-pyridinecarboxamido)-2-(2-pyridiyl)indolizine (2) was readily synthesized by the one-pot reaction of 2-(cyanomethyl)pyridine (la) with selenium dioxide. The reaction of 3- or 4-(cyanomethyl)pyridines (lb,c) under the same reaction conditions gave 2,3-bi(3-pyridyl)-2-butenedinitrile (3b) and 2,3-bi(4-pyridyl)-2-butenedinitrile (3c), respectively. The indolizine 2 (L-H) reacted with Ni(NO 3 ) 2 ·6H 2 O in ethanol to produce the NiL 2 complex (4). The structure was determined by X-ray crystallography.