Silaethene: XIII. Erzeugung von SiC-Doppelbindungen in der Koordinationssphäre von Eisencarbonylkomplexen

Abstract The suitability of the vinylsilyliron complexes [Cp(CO) 2 Fe]RSi(Cl)CHCH 2 [R = Me ( 1 ), Ph ( 2 ), Bu t ( 3 ), Fe(CO) 2 Cp ( 4 )] and of [Cp(CO) 2 Fe]MeSi(Cl)CMeCH 2 ( 14 ) as precursors for the generation of silaethene derivatives has been investigated. The starting compounds 1 to 4 and 14 can be obtained from Me(Vi)SiCl 2 , Ph(Vi)SiCl 2 , HSiCl 3 and MeSiCl 3 , respectively, by judicious combination of published procedures. They have been characterized by analytical and spectroscopic studies as well as by comparison with known data. The generation of the SiC intermediates was attempted by treating the vinylsilyl iron complexes wit LiBu t at low temperatures (−10°C). Only with 1 was a smooth reaction observed with formation of the Z Z dimer 1,3-bis(cyclopentadienyl-dicarbonyliron)-1,3-dimethyl-2,4-dineopentyl-1,3-disilacyclobutane ( 16 ) of the expected silaethene [Cp(CO) 2 Fe]-MeSiCHCH 2 Bu t . This intermediate also seems plausible on the basis of trapping experiments, using 2,3-dimethyl-1,3-butadiene, isoprene or 1,3-cyclohexadiene. However, since 16 is formed as the main product even in the presence of an excess of these dienes, the cyclization of the lithiated precursor ClSiMe[Fe(CO) 2 Cp]-CH(CH 2 Bu t )SiMe[Fe(CO) 2 Cp]CH(Li)CH 2 Bu t must be regarded as an alternative route to 16 . The crystal and molecular structure of 16 indicate a Z Z configuration of the bulky ring substituents. The disilacyclobutane skeleton is nonplanar with a dihedral angle of 18.7°. Similar to other 1,3-disilacyclobutane derivatives, 16 shows a fairly short transannular Si(1)⋯Si(2) distance of 2.641(1) A. Due to the −I effect of the phenyl substituent reaction of 2 with LiBu t yields oligomeric coupling products, whereas in 3 , 4 or 14 for steric reasons LiBu t clearly attacks the carbonyl ligand instead of the CC double bond to give black, pyrophoric solids of low solubility.