Synthesis and crystal structures of two iron derivatives of permethylcyclopentasilane

Abstract

Reaction of dodecamethylcyclohexasilane with Me 3SiCl and AlCl 3 produces a mixture of cyclo-Si 5Me 9SiMe 2Cl (Ia) and cyclo-Si 5Me 8ClSiMe 2Cl (III). Treatment with [Fe(CO) 2Cp] − produced cyclo-Si 5Me 9SiMe 2[Fe(CO) 2Cp] (II) and cyclo-Si 5Me 8[Fe(CO) 2Cp]SiMe 2[Fe(CO) 2Cp] (IV). The structures of II and IV were determined by single crystal X-ray diffraction. Compound II crystallizes in the monoclinic space group P2 1/ c with a 21.531(9) Å, b 9.865(4) Å, c 13.917 Å, β 101.67(2)°, V 2895(2) Å 3 and with Z = 4. Compound IV crystallizes in the monoclinic space group P2 1/ c with a 7.923(2) Å, b 22.504(9) Å, c 19.168(7) Å, β 92.86(3)°, V 3413(2) Å 3 and with Z = 4. The cyclopentasilane fragment of II is in a C s conformation, with four silicon atoms coplanar and the remaining silicon 1.02 Å out of the plane, forming a dihedral angle of 137°. In the silicon ring the average SiSiSi bond angle is 104(2)° and the average SiSi bond length is 2.356(10) Å. In compound IV the second iron atom is attached at the 2 position on the cyclopentasilane ring, which is in a distorted C s , conformation with average SiSi bond length 2.326(2) Å and average SiSiSi bond angle 104(2)°.