Übergangsmetall-koordinierte heteroalkene als synthesebausteine: Nachweis und charakterisierung einer zwischenstufe der reaktion von thio- und selenoaldehyd-komplexen mit bis(diethylamino)acetylen

Abstract Pentacarbonyl(thiobenzaldehyde)- and -(selenobenzaldehyde)tungsten, (CO) 5 W[XC(Ph)H] [X = S ( 1a ), Se ( 1b )] react with bis(diethylamino)acetylene, Et 2 NCCNEt 2 ( 2 ), by addition of the alkyne to the XC bond under electrocyclic ring opening to give substituted pentacarbonyl(thioacrylamide)- and -(selenoacrylamide)tungsten complexes, (CO) 5 W[XC(NEt 2 )C(NEt 2 )C(Ph)H]. The kinetically controlled reaction product is the Z -isomer (with respect to the CC double bond) ( 3 ). In a subsequent, slower reaction, 3 isomerizes to give the E -isomer 4 . 3b isomerizes more rapidly than 3a . For the isomerization of 3a to 4a the free enthalpy of activation Δ G ≠ is 102 kJ/mol (at 40°C in CD 3 COCD 3 ). The complex 3a was isolated and its structure established by an X-ray diffraction study.