Reactions of complex ligands Part 91. Application of ring closing metathesis to Fischer-type carbene complexes: synthesis and structure of medium-sized chromium oxacycloalkenylidenes

Six- and seven-membered pentacarbonyl(2-oxacycloalkenylidene) chromium comp lexes 17 and 6 have been synthesized in moderate to good yields from alkeny loxy(methyl)carbene complex precursors applying an alpha-alkylation/rutheni um based ring closing metathesis sequence. The ring-closure is hampered for beta-alkylated vinylcarbene complexes which may undergo competing intermol ecular cross metathesis at the alkenyloxy terminus in low yield. (C) 2000 E lsevier Science S.A. All rights reserved.