SYNTHESIS AND REACTIONS OF ENANTIOPURE (NEOMETHYLCYCLOPENTADIENYL)IRIDIUM(III) HALIDES WITH SILVER SALTS - A DRAMATIC STERIC EFFECT ON THE COMPETITION BETWEEN INTERMOLECULAR AND INTRAMOLECULAR C-H ACTIVATION

Reactions of enantiomerically pure (NMCp)M-(PMe3)(Me)X complexes (NMCp = neomenthylcyclopentadienyl; M = Rh, Ir) have revealed that the 16-e lectron (NMCp)M(Pme3)(Me)+ intermediates are achiral (planar) at the m etal centers on the time average. Generation of the presumed intermedi ate (NMCp)Ir-(Pme3) by photolysis of (NMCp)Ir(Pme3)(H)2 in the presenc e of hydrocarbons results in intermolecular C-H activation. In contras t, the presumed intermediate (NMCp)M(Pme3)(Me)+ exhibits only intramol ecular C-H activation involving the neomenthyl group. One of these cyc lometalation products has been structurally characterized. The differe nt outcomes of these two systems are attributed to energy differences in the transition states based on molecular mechanics calculations.