The mechanism of aromatic C–C bond cleavage in quinoxaline (QoxH) catalyzed by the tungsten complexes W(PMe3)4(η2-CH2PMe2)H has been theoretically investigated at the DFT level. The mononuclear species (η2(N,C)-Qox)W(PMe3)4H (experimentally isolated and characterized) is directly involved in the formation of the final product [κ2(C2)-C6H4(NC)2]W(PMe3)4, where the aromatic C–C bond of quinoxaline has been broken. The mechanism requires a double insertion of the metal into two quinoxaline C–H bonds, thus affording the “strained” benzyne-type species η2(C2)-C6H4(NCCN)W(PMe3)4H2. After expulsion of H2 the η2(C2) complex leads to the [κ2(C2)-C6H4(NC)2]W(PMe3)4 product, thus relieving the structural strain of the small WCC cycle in η2(C2). Also, the theoretical investigation shows the existence of a stable (η4(C2N2)-QoxH)W(PMe3)3H2 complex (an unprecedented example of η4 coordination), in agreement with its experimental observation and characterization by X-ray diffraction.
G. P. Miscione, M. A. Carvajal, A. Bottoni (2011). “Aromatic Carbon–Carbon Bond Cleavage Using Tungsten Complexes. A DFT Computational Study”. ORGANOMETALLICS, 30, 4924-4934 [10.1021/om2005029].
“Aromatic Carbon–Carbon Bond Cleavage Using Tungsten Complexes. A DFT Computational Study”
MISCIONE, GIAN PIETRO;BOTTONI, ANDREA
2011
Abstract
The mechanism of aromatic C–C bond cleavage in quinoxaline (QoxH) catalyzed by the tungsten complexes W(PMe3)4(η2-CH2PMe2)H has been theoretically investigated at the DFT level. The mononuclear species (η2(N,C)-Qox)W(PMe3)4H (experimentally isolated and characterized) is directly involved in the formation of the final product [κ2(C2)-C6H4(NC)2]W(PMe3)4, where the aromatic C–C bond of quinoxaline has been broken. The mechanism requires a double insertion of the metal into two quinoxaline C–H bonds, thus affording the “strained” benzyne-type species η2(C2)-C6H4(NCCN)W(PMe3)4H2. After expulsion of H2 the η2(C2) complex leads to the [κ2(C2)-C6H4(NC)2]W(PMe3)4 product, thus relieving the structural strain of the small WCC cycle in η2(C2). Also, the theoretical investigation shows the existence of a stable (η4(C2N2)-QoxH)W(PMe3)3H2 complex (an unprecedented example of η4 coordination), in agreement with its experimental observation and characterization by X-ray diffraction.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.