Tetrasilabutadiene 1,4 addition reaction

Addition Reactions. While cycloadditions to 6 are still exceedingly rare, reactions of 6 with small molecules, as summarized in Scheme 8.1, were more successful. Treatment of the tetrasilabutadiene with small amounts of water led, via the 1,2-addition product 16 to the rearranged oxatetrasilacyclopentane 17, an analogue of tetrahydrofuran. With an excess of water the tetrasilane-l,4-diol 18 was obtained, which showed no tendency to eliminate water with the formation of 17. ... 

Keywords silylenes, disilenes, tetrasilabutadiene, multiple bonds, addition reactions, cycloadditions, germanium compounds... 

The reaction of tetrasilabutadiene 64 with Cl2 gives 1,2,3,4-tetrachlorotetrasilane 182 [Eq. (86)].125 As chlorine gas is added, the solution of 64 turns from dark red to blue-black to orange, and finally to colorless. On this basis, the addition is proposed to proceed stepwise via the initial formation of a charge-transfer complex between 64 and Cl2 to give 183, which is converted to disilene 184 and then to 182 by the addition of a second molecule of Cl2. 

Reactions. Experimental results of reactions of (Tip)2 Si= Si(Tip) Si(Tip)=Si(Tip)2 are summarized in Scheme 40. Treatment of the tetrasilabutadiene with a small amount of water gave an analog of tetrahydrolhran, an oxatetrasilolane derivative, probably via the 1,2-addition and the following rearrangement. Addition of an excess amount of water resulted in the formation of the tetrasila-l,4-diol derivative, which showed no tendency to ehminate water with the formation of the oxatetrasilolane derivative. 

In the following text, results concerning the syntheses and reactions of disilenes of types 1-4 are presented. In addition, dehalogenations of the disilenes 2 and 4, and dehydrobromination of the disilane R HBrSi-SiBrHR, which possibly lead to disilynes of types 5-7, will be described (in some cases, these reactions obviously proceed via cyclotrisilenes as well as cyclotetrasilenes and even tetrasilabutadienes). The disilenes 1 (R = Ph), 3, and 4 and, (obviously) the disilyne 7, could be obtained under normal conditions due to an adequate steric shielding of the reactive >Si=Si< and -Si Si- entities with bulky silicon-bound groups. 

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