Propargyl ligands

The recently reviewed chemistry of the -aUenyl and propargyl ligands has significant contributions from Re complexes. U -propargyl derivatives of the ReCp (CO)2 fragment (80) have been prepared either by H abstraction from alkyne complexes ReCp (CO)2(RC=CR) or... 

In the polynuclear framework [see Polynuclear Organometallic Cluster Complexes, allenyl and propargyl ligands are often bound to the metals with various crossing interactions, which serve to bring the metal atoms into close proximity and stabilize the hydrogen-deficient organic moiety. In the... 

The jt-allyl ligand bonded to cationic Pd(II) center tends to undergo nucleophilic substitution by organic nucleophiles from the opposite side of the metal center (Chapter 8). Attack of Pd(0) or Pt(0) complex in this fashion causes inversion of stereochemistry of the complex repetition of the reactions results in epimerization. The allyl ligand transfer between Pd centers takes place much faster than that from Pd to Pt. Isomerization between the Pt(II) complexes with a propargyl ligand and that with an allenyl ligand is catalyzed by Pd(0) complex (Eq. 5.58) [200,201]. 

The propargyl ligand is electronically analogous to the allyl if both are bound to the metal via 7 -coordination. If bound in the 7 -form, the former may generate considerably higher strain compared to the 7 -allyl system. The 7 -propargyl ligand... 

Electrophilic attack also occurs at the -Y-position of propargyl ligands, and this reaction converts propargyl complexes to allene complexes. An example of this protonation process is shown in Equation 12.61. This reaction has been used to initiate cycloaddition reactions. An example of this type of cycloaddition is the [3-t2] reaction of p-toluenesulfonyl isocyanate with the propargyl complex in Equation 12.62. Propargyl and Ti -allyl ligands are about equally reactive toward such cycloadditions. 

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