(η⁵‐Cyclopentadienyl)(η⁴‐tetrasila‐ and η⁴‐trisilagermacyclobutadiene)cobalt: Sandwich Complexes Featuring Heavy Cyclobutadiene Ligands

Abstract

Abstract (η 5 ‐Cyclopentadienyl)(η 4 ‐tetrasilacyclobutadiene)cobalt{[(η 4 ‐R 4 Si 4 )CoCp], 2 } and (η 5 ‐cyclopentadienyl)(η 4 ‐trisilagermacyclobutadiene)cobalt {[(η 4 ‐R 4 Si 3 Ge)CoCp], 4 } (R = SiMe t Bu 2 ) were synthesized by reaction of the dipotassium salts of tetrasilacyclobutadiene dianion K + 2 · [R 4 Si 4 ] 2– ( 1 ) and trisilagermacyclobutadiene dianion K + 2 · [R 4 Si 3 Ge] 2– ( 3 ) with [CpCoI 2 (PPh 3 )]. Alternatively, 4 was prepared by the reaction of 3 with [Cp 2 Co] + · [PF 6 ] – . X‐ray crystallographic analysis of 2 confirmed its sandwich‐type structure, manifesting a nearly square‐planar Si 4 ring and diagnostic perhaptocoordination of both ligands, η 4 ‐tetrasilacyclobutadiene and η 5 ‐cyclopentadienyl, to the Co atom. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)