Nickel-catalysts supported by phosphines, amines, and N-heterocyclic carbenes have been widely used in the development of important C-C and C-heteroatom reactions.[1-4] In many cases, Ni-NHC complexes were found to facilitate more-efficient transformations and complementary selectivities compared to phosphine and amine-based systems. Typically, Ni-NHC catalysts were prepared in situ from Ni(COD)2 and ligand.[4] Unfortunately, however, in situ generation of these catalysts can be problematic due to increased sensitivity of Ni-NHC systems to metal-ligand stoichiometry than those with phosphine or amine ligands.[4-6] To address this challenge, researchers at the University of Michigan sought to develop a new class of discrete Ni(0) catalysts with pre-defined 1:1 NHC–metal stoichiometry. Remarkably, stabilization of an electron-rich [Ni-NHC] metal fragment with electron deficient olefins (e.g. methyl methacrylate, di-tert-butyl fumarate) was found to give well-defined, highly active, air-tolerant pre-catalysts of broad utility.[7]
Strem is proud to announce the release of this technology to customers. As shown in Fig. 1, pre-catalysts featuring IMes 28-1040 and 28-1050 NHC-ligands[7] are now available for purchase by catalog or website.
Fig. 1. New, well-defined Ni(0)-NHC catalysts available from Strem.
So far, catalytic activity and efficiency of representative members of (NHC)−Ni(0) catalysts have been evaluated in reductive coupling of aldehydes and alkynes and in N-arylations of amines. Importantly, however, this class of catalysts are expected to be suitable for a wide array of Ni(0)-catalyzed processes.[7]
References:
Products Mentioned & Related Resources:
28-1040: Bis(di-tert-butyl fumarate)(1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene)nickel(0), 96% (2091838-72-9)
28-1050: Bis(methyl methacrylate)(1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene)nickel(0), 98% (2230140-51-7)