Silaethane XIII. Erzeugung von SiC-Doppelbindungen in der Koordinationssphaere von Eisencarbonylkomplexen

Article abstract of DOI:10.1016/0022-328X(89)88036-2

The suitability of the vinylsilyliron complexes RSi(Cl)CH=CH2 t (3), Fe(CO)2cp (4)> and of MeSi(Cl)CMe=CH2 (14) as precursors for the generation of silaethane derivatives has been investigated.The starting compounds 1 to 4 and 14 can be obtained from Me(Vi)SiCl2, Ph(Vi)SiCl2, HSiCl3 and MeSiCl3, 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 with LiBu^t at low temperatures (-10 deg 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 silaethane MeSi=CHCH2Bu^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 ClSiMeCH(CH2Bu^t)SiMeCH(Li)CH2Bu^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 deg.Similar to other 1,3-disilacyclobutane derivatives, 16 shows a fairly short transannular Si(1)...Si(2) distance of 2.641(1) Angstroem.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.