Abstract
Abstract The reaction of 3,3,6,6,8,8,11,11,14,14,16,16,19,19,21,21-hexadecamethyl-3,6,8,11,14,16,19,21-octasilacyclohenicosa-1,4,9,12,17-pentayne with an excess molar amount of [Mn(CO)3(Me-Cp)] in tetrahydrofuran (THF) under photochemical and refluxing conditions produced 2,2,4,4,9,9,11,11,13,13,15,15,17,17,21,21-hexadecamehyl-2,4,9,11,13,15,17,21-octasilahexacyclo[10.5.3.15,8.06,18.07,20.014,19]henicosa-1(18),5,7,12(20),14(19)-pentaene (2) as silyl-substituted [5]radialene derivative. This was reacted with lithium metal in THF to give dark red crystals of the tetralithium salt (4) of 2. The molecular structure of tetraanion of 2 with a novel ten-center, fourteen-electron π-system was established by X-ray crystallography. The tetralithium salt 4 has a monomeric structure and forms contact ion pairs (tetrakis-CIPs) in the crystals. The structural parameters of 4 are discussed in comparison with those of the neutral starting molecule 2. The structure of 4 in solution is also discussed on the basis of NMR spectroscopic data.
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