Kinetics of the BpCu-catalyzed carbene transfer reaction (Bp equals dihydridobis(1-pyrazolyl)borate). Is a 14-electron species the real catalyst for the general copper-mediated olefin cyclopropanation?

Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in t he presence of BpCu (1) and in the presence or absence of olefin have led t o the determination of several kinetic and thermodynamic parameters, and a consistent mechanism has been proposed for the olefin cyclopropanation reac tion. Related studies with the complexes [Cu(bipy)(2)]I (bipy = bipyridine) and [Cu(bis(oxazoline))(2)]OTf have shown strong similarities with the res ults obtained with 1. A general mechanism covering the copper-based systems reported in the literature has been proposed, the real catalyst (i.e., the species to be reacted with EDA) in all cases being a neutral, 14-electron fragment of composition (L-L)Cu (L-L = Bp- and Tp-like ligands, semicorrins , salicylaldehyde derivatives) or, alternatively, the isoelectronic, cation ic [(L-L)Cu](+) (for L-L = bis(oxazoline), bipyridine).