Controlled Conversion of the Transient 2‐Mesityl‐1,1‐bis(trimethylsilyl)silene into a Tetrahydro‐2,3‐disilanaphthalene, a 1,2‐Disilacyclobutane, or a 1,3‐Disilacyclobutane
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E-Article
Title:
Controlled Conversion of the Transient 2‐Mesityl‐1,1‐bis(trimethylsilyl)silene into a Tetrahydro‐2,3‐disilanaphthalene, a 1,2‐Disilacyclobutane, or a 1,3‐Disilacyclobutane
Description:
<jats:title>Abstract</jats:title><jats:p>Mesityl[tris(trimethylsilyl)silyl]methanol (<jats:bold>1</jats:bold>) reacts with strong bases with elimination of trimethylsilanolate according to a Peterson‐type mechanism, the outcome of the reaction being dependent on solvent, temperature, and nature of the organometallic base applied. Thus, <jats:bold>1</jats:bold> was converted by treatment with MeLi in ether at –78°C to (<jats:italic>E</jats:italic>)‐1,2,3,8a‐tetra ‐hydro‐1‐mesityl‐5,7,8a‐trimethyl‐2,2,3,3‐tetrakis (trimethylsi‐lyl)‐2,3‐disilanaphthalene (<jats:bold>3</jats:bold>), formally a [2 + 4] cyclodimer of the transient silene (Me<jats:sub>3</jats:sub>Si)<jats:sub>2</jats:sub>Si=CHMes (<jats:bold>2</jats:bold>). The reaction of <jats:bold>1</jats:bold> with PhMgBr in THF after some days resulted in the formation of (<jats:bold>Z</jats:bold>)‐3,4‐dimesityl‐1,1,2,2‐tetrakis(trimethylsilyl) ‐1,2‐disilacyclobutane (<jats:bold>6</jats:bold>) as the main product besides small quantities of <jats:bold>3</jats:bold>, the polysilane (Me<jats:sub>3</jats:sub>SiSi(SiMe<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>Mes (<jats:bold>10</jats:bold>), and the alkoxysilane (Me<jats:sub>3</jats:sub>Si)<jats:sub>3</jats:sub>SiCH(Mes)OSi(Si‐Me<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>Mes (<jats:bold>7</jats:bold>). Compound <jats:bold>6</jats:bold>, the formal [2 + 2] cycloadduct of <jats:bold>2</jats:bold>, can also be obtained by thermal treatment of <jats:bold>3</jats:bold> and is considered to be the thermodynamically more stable silene dimer whereas <jats:bold>3</jats:bold> is the kinetically preferred product. At high LiBr concentrations in the reaction mixture <jats:bold>1</jats:bold> was converted by PhMgBr in THF to (<jats:italic>E</jats:italic>)‐2,4‐dimesityl‐1,1,3,3‐tetrakis(tri‐ methylsilyl)‐1,3‐disilacyclobutane (<jats:bold>13</jats:bold>) besides <jats:bold>6</jats:bold> and [bis(tri‐methylsilyl)silyl]mesityl(trimethylsiloxy)methane (<jats:bold>11</jats:bold>). The unforeseen formation of <jats:bold>13</jats:bold> is discussed as proceeding via the silene‐lithium bromide adduct (Me<jats:sub>3</jats:sub>Si)<jats:sub>2</jats:sub>Si(Br)CH(Li)Mes (<jats:bold>12</jats:bold>). In the absence of LiBr <jats:bold>1</jats:bold> was converted by MeLi in THF at –78°C to <jats:bold>11</jats:bold> and the trisilane (Me<jats:sub>3</jats:sub>Si)<jats:sub>2</jats:sub>Si(Me)CH<jats:sub>2</jats:sub>Mes (<jats:bold>4b</jats:bold>). Probable pathways of the formation of all new compounds are discussed. For <jats:bold>6</jats:bold> and <jats:bold>13</jats:bold> the results of the X‐ray structural analyses are given.</jats:p>