10.1021/acs.organomet.9b00507.s001
Michael Haas
Michael
Haas
Andreas Knoechl
Andreas
Knoechl
Tanja Wiesner
Tanja
Wiesner
Ana Torvisco
Ana
Torvisco
Roland Fischer
Roland
Fischer
Cameron Jones
Cameron
Jones
Attempted Synthesis of a Homocyclic Bis(silyl)silylene
Leads to the Formation of a Tricyclo[3,1,1,1<sup>2,4</sup>]octasilane
American Chemical Society
2019
Et 3 SiH
endocyclic disilene 1
hexasilanes 10
2.1 equiv
formation
dianionic compound 13
salt metathesis reaction
KO
Dianionic species 12
2019-10-07 19:52:03
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Attempted_Synthesis_of_a_Homocyclic_Bis_silyl_silylene_Leads_to_the_Formation_of_a_Tricyclo_3_1_1_1_sup_2_4_sup_octasilane/9946997
The
reduction of 1,1-dibromo-cyclopentasilane with a mildly reducing
magnesium(I) dimer [{(MesNacnac)Mg−}<sub>2</sub>] was examined,
which gave rise to the formation of endocyclic disilene <b>1</b>. The formation of <b>1</b> was further confirmed by a trapping
experiment with MeOH. Additionally, <b>1</b> was found to dimerize
slowly to <b>1-dimer</b>. Furthermore, the formation of the
homocyclic silylene was demonstrated by performing the reduction in
the presence of Et<sub>3</sub>SiH as a trapping agent. To prevent
the 1,2-trimethylsilyl shift, which causes a rapid degradation of
the silylene, a second synthetic strategy was established. Therefore,
two different tetrasilanes <b>4</b> and <b>5</b> were
synthesized. Compounds <b>4</b> and <b>5</b> were subsequently
reacted with 2.1 equiv of trifluoromethanesulfonic acid to corresponding
bis(trifluoromethanesulfonates) <b>6</b> and <b>7</b>.
1,4-Dihalo-tetrasilanes <b>8a</b>,<b>b</b> and <b>9</b> as well as hexasilanes <b>10</b> and <b>11</b> were
obtained by a subsequent nucleophilic substitution of the triflate
substituent with X<sup>–</sup> (X = Cl<sup>–</sup>,
Br<sup>–</sup>, or R<sub>3</sub>Si<sup>–</sup>). Dianionic
species <b>12</b> and <b>13</b> were synthesized by the
reaction of corresponding hexasilanes <b>10</b> and <b>11</b> with 2.1 equiv of KO<i>t</i>-Bu. Surprisingly, the salt
metathesis reaction of dianionic compound <b>13</b> does not
lead to the formation of the expected 1,1-halocyclopentasilanes. Instead
the formation of cyclobutasilane <b>14</b> was observed. The
reaction of <b>9</b> with lithium led again to the formation
of <b>14</b> alongside with the formation of cyclohexasilane <b>15</b>. Interestingly, <b>14</b> underwent a ring-opening
formation by the reaction with gaseous HCl in the presence of AlCl<sub>3</sub> and compound <b>16</b> was formed. The reduction of <b>16</b> allowed straightforward access to <b>17</b> as a
structurally complex hitherto unknown tricyclic polysilane.