Four palladium chelate complexes with S‐ or Se‐containing substituted salicylaldehyde Schiff‐base derivatives have been synthesized. Spectroscopic and crystallographic data indicate that, in the complexes, the deprotonated salicylaldehyde ligand is bound to the metal in an O,N,S (or Se)‐terdentate coordination mode, forming one six‐ and one five‐membered chelate ring. The complexes are thermally and air stable and efficiently catalyze the Suzuki–Miyaura cross‐coupling of aryl bromides with phenylboronic acid in air.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Regio- and stereoselective reactions accompanied by rearrangements with ring extension or contraction.

Regio- and stereoselective ring-opening reaction of 2-bromomethyl-1,3-thiaselenole with thiols proceeded as nucleophilic attack at the selenium atom of seleniranium intermediate affording unsaturated selanyl sulfides, (Z)-CH2=CHSCH=CHSeSR, in up to 93% yield. Dithiols were involved in this reaction giving symmetrical polyunsaturated compounds with two S–Se bonds in 70–75% yields. Efficient synthesis of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines in 69–96% yields was developed by the acid-catalyzed cyclization of the unsaturated selanyl sulfides. Mild reaction conditions (room temperature) and short reaction times are important features of this methodology.

The reaction of 2-(bromomethyl)-1,3-thiaselenole with potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on the generation of sodium 1,3-thiaselenol-2-ylmethylselenolate from 1,3-thiaselenol-2-ylmethyl selenocyanate or bis(1,3-thiaselenol-2-ylmethyl) diselenide followed by nucleophilic substitution reactions. Sodium 1,3-thiaselenol-2-ylmethylselenolate underwent nucleophilic addition to alkyl propiolates in a regio- and stereoselective manner affording 1,3-thiaselenol-2-ylmethyl vinyl selenides in high yields predominantly with Z-configuration. Not a single representative of the 1,3-thiaselenol-2-ylmethyl selenide scaffold has been previously described in the literature.

A series of organoselanyl-and organotellanyl-substituted ethyl-and propylamines and their hydrochlorides, as well as 2-(methylsulfanyl)ethylamine have been synthesized. Efficient general synthetic routes have been developed to chalcogen(S, Se, Te)-containing Schiff bases with di-and trimethylene bridges between the nitrogen atom of the imino group and the chalcogen, by condensation of 3-(tert-butyl)-and 3-(1-ethylpropyl)-2-hydoxybenzenecarbaldehydes with the amines. The influence of the organylchalcogenyl-group on some spectral characteristics ( 1 H, 13 C, 77 Se NMR spectroscopy) of both amines and Schiff bases is discussed.Schiff bases are among the most investigated ligands in coordination chemistry, 1 but interest in them remains high, due partly to the wide range of possibilities for varying the substituents in these ligand systems and also because of their potential applications in homogeneous catalysis. One class of Schiff bases, which has received particular attention, is that of the bidentate salicylaldimines formed by the reaction of o-hydroxybenzaldehydes with the corresponding amines. Use of amines which incorporate alkylamino-, hydroxy-, alkoxy-, alkyl-and arylthio groups capable of additional coordination leads to the possibility of an increase in denticity of the ligand in complex formation. 2 An alternative procedure for the preparation of this type of ligands containing sulfur consists of electrochemical rupture of the disulfide bond of the corresponding bis-2-salicylaldiminoethyl disulfides. 3 Large 24-and 28-membered macrocyclic Schiff bases are also known with selenide and telluride functions linked to the nitrogen atom of the imine bond through polymethylene bridges (CH 2 ) n (n = 2,3). 4 Schiff bases bearing a sulfide group connected to the nitrogen atom of the imine function by a dimethylene bridge are formed by condensation of 2-(organosulfanyl)ethylamine, 2-[(2-aminoethyl)thiomethyl]benzimidazole or imidazole, with substituted salicylaldehydes, 5 acetophenone or acetylacetones. 6Taking into account the potential of these Schiff bases as tridentate ligands, 1 and at the same time the extremely scarce knowledge about these compounds, which is limited mainly to sulfur-containing derivatives, we have synthesized salicylaldimines bearing sulfide-, selenide-and telluride functions connected to nitrogen by a polymethylene bridge (CH 2 ) n (n = 2,3) starting from 3-(tert-butyl)-and 3-(1-ethylpropyl)-2-hydroxybenzenecarbaldehydes and a series of 2-(organylselanyl)ethylamines 6, 2-(organyltellanyl)ethylamines 7, 3-(organylselanyl)propylamines 8, and 3-(organyltellanyl)propylamines 9 synthesized by us. For comparison purposes we have also prepared the analogous Schiff bases using 2-(methylsulfanyl)ethylamine 5.It should be pointed out that terminal organylchalcogenylalkylamines in themselves are prospective ligands, which has been shown for N-{2-(4-methoxyphenyltellanyl)ethyl}morpholine, 7 bis-{2-(N-morpholino)ethyl}telluride, 7b 3-organylselanyl(tellanyl) propylamines, 8 2-organylselanylethylamine, ...

a b s t r a c tRegio-and stereoselective reactions of selenium dihalides with diorganyl diethynyl germanes in CHCl 3 afford in yields from preparative to quantitative the first representatives of a new class of selenium-germanium containing heterocycles -3,6-dihalogen-4,4-diorganyl-1,4-selenagermafulvenes. The reaction of selenium tetrachloride under the same conditions leads to the first representatives of a new class of selenium-germanium containing cyclopentene heterocycles -2-dichloromethyl-2,4-dichloro-3,3-diorganyl-1-selena-3-germacyclopentenes-4 as well as to the unknown 3,6,6-trichloro-4,4-dialkyl-1,4-selenagermafulvenes formed as a result of a spontaneous dehydrochlorination of the cyclopentene heterocycles. In a case of SeBr 4 the process of dehydrobromination is dominating. The structures of the heterocycles were proved by multinuclear ( 1 H, 13 C, 77 Se) spectroscopy and mass-spectrometry. In the 1 H NMR spectra of Z-isomers of 1,4-selenagermafulvenes a long-range spin-spin interaction between exo-and endocyclic olefinic protons through five bonds is revealed lacking in the E-isomers.

The first organic metals were obtained based on tetrathiafulvalene. The most significant advance in the field of organic metals was the discovery of superconductivity. The first organic superconductors were obtained based on tetramethyltetraselenafulvalene. These facts demonstrate great importance of tetraselenafulvalenes and their precursors, diselenafulvenes, for materials sciences. Derivatives of 1,4-diselenafulvene and 1,4,5,8-tetraselenafulvalene are useful building blocks for organic synthesis and donor units for the preparation of charge-transfer complexes and radical ion salts, the construction of organic metals, superconductors, organic Dirac materials, semiconductors, ferromagnets, and other conductive materials. This review covers the literature on the design, synthesis, and application of 1,4,5,8-tetraselenafulvalenes and 1,4-diselenafulvenes and their tellurium analogs over the past 15–20 years. These two classes of compounds are interconnected, since the main part of methods for the synthesis of tetraselenafulvalenes is based on the diselenafulvene derivatives as starting compounds. Special attention is paid to the development of novel efficient synthetic approaches to these classes of compounds. Conducting properties and distinguishing features of materials based on tetraselenafulvalenes and their tellurium analogs as well as examples of materials with high conductivity are discussed.

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