Silicon—selenium bonds

Palladium-catalyzed addition of the selenium-silicon bond of PhSe-SiMe3 to arylacetylenes proceeds in a regio- and stereoselective manner to afford (Z)-a-(phenylseleno)-/ -(trimethylsilyl)styrenes (Equation (123)).250 Aliphatic alkynes fails to undergo the addition reaction. Analogous addition of the Se-Ge bond to alkynes occurs under similar conditions. 

Element-element bonds, addition to G-G multiple bonds arsenic—selenium bonds, 10, 782 boron—boron bonds, 10, 727 boron—sulfur bonds, 10, 778 B-S and B-Ge bonds, 10, 758 chalcogen—chalcogen additions, 10, 752 germanium—germanium bonds, 10, 747 germanium-tin bonds, 10, 780 overview, 10, 725-787 phosphorus—phosphorus bonds, 10, 751 phosphorus—selenium bonds, 10, 782 phosphorus-sulfur bonds, 10, 781 Se-Si and Se-Ge bonds, 10, 779 silicon-germanium bonds, 10, 770 silicon-phosphorus bonds, 10, 780 silicon-silicon bonds, 10, 734 silicon-sulfur bonds, 10, 779 silicon-tin bonds, 10, 770 tin-boron bonds, 10, 767 tin-tin bonds, 10, 748... 

Selenium-silicon and selenium-germanium bonds. Similar to boron, silicon shields Se nuclei when attached. In addition to those compounds published prior to 1995, a large number of papers have appeared reporting Se-Si and Se-Ge bonds in various constellations, a representative choice of which is illustrated below. 

A new and potentially valuable photochemical route to tetra-methyldisilene (175) has been reported and involves irradiation of 7,7,8,8-tetramethyl-7,8-disilabicyclo[2.2.0]octa-2,5-diene(176)in an argon matrix at 10 the disilene readily undergoes [ 4 + 2] cycloaddition to benzene to regenerate the precursor. The silane-selenones (177), reactive intermediates with a silicon-selenium double bond, can be photochemically generated and trapped with hexamethylcyclotrisiloxane as shown in Scheme 9. Irradiation of hexamesitylcyclotrisilane (178) in the presence of azobenzene... 

Photolysis of cyclic silicon-selenium ring systems (analogs of D3, (Me2SiO)3) apparently generated compounds with silicon-selenium double bonds these were trapped with hexamethylcyclotrisiloxane to yield the two-atom insertion products158 (equation 100). 

The methods available for synthesis have advanced dramatically in the past half-century. Improvements have been made in selectivity of conditions, versatility of transformations, stereochemical control, and the efficiency of synthetic processes. The range of available reagents has expanded. Many reactions involve compounds of boron, silicon, sulfur, selenium, phosphorus, and tin. Catalysis, particularly by transition metal complexes, has also become a key part of organic synthesis. The mechanisms of catalytic reactions are characterized by catalytic cycles and require an understanding not only of the ultimate bond-forming and bond-breaking steps, but also of the mechanism for regeneration of the active catalytic species and the effect of products, by-products, and other reaction components in the catalytic cycle. 

Silicon-Selenium and Silicon-Tellurium Double Bond Compounds... 

Germylene insertion into germacyclobutanes to give 1,2-digermacyclopentanes has already been described (Scheme 88). However, the tetraethyl derivative (95) is better made via the mercury derivative (Scheme 162). Like its silicon counterpart, (95) is slowly oxidized at room temperature, and inserts sulfur, selenium and bromine in the Ge—Ge bond. While (95) is less stable than the 1,2-digermacyclohexane, dichlorocarbene inserts into the /3-C—H bond of both rings, and not the Ge—C bond (Scheme 163) (69JOM(16)227). 

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