MONONUCLEAR TRANSITION-METAL ETA-3-PROPARGLY ALLENYL COMPLEXES - SYNTHESIS, STRUCTURE AND REACTION CHEMISTRY

Synthetic approaches to a new class of monomeric transition-metal eta3 -propargy/allenyl complexes are presented. X-ray crystallographic stud ies on several such complexes show that the eta3-C3 fragment is bent a nd that the eta3-hydrocarbyl ligand is best considered as a hybrid of eta3-propargyl and eta3-allenyl resonance structures. H-1 and C-13 NMR data are in accord with such a description of the bonding. Reaction c hemistry of these complexes is characterized by the addition of nucleo philes at the central carbon atom of the eta3-propargyl/allenyl ligand , although addition at the metal to reduce ligand hapticity from eta3 to eta1 has also been encountered for the sterically less crowded meta l systems.