The impact of earth-abundant metals as a replacement for Pd in cross coupling reactions

Abstract

Substitution of one metal catalyst for another is not straightforward as simply justifying this change based on the availability and/or cost of the metals. A life cycle-like assessment was performed...

Ni-NHC Nanoparticles in Micelles as an Effective and Reusable Catalyst for Hydrogenations and Reductive-Aminations in Water

“…38−40 abundant transition metals, which have been less applied in catalysis and which have become a priority for economical reasons that are not necessarily valid considering climate change and environment. 33 Thus, to the best of our knowledge, there are only five reports on the use of NHC ligands to stabilize Ni NPs and catalyze chemical reactions, such as Kumada couplings, carbonyl hydrosilylations, and alkyne semihydrogenation. 41−45 In particular, we have recently reported Ni nanoparticles coordinated to NHC ligands bearing an N-coordinated cinnamyl moiety that are readily prepared by the reduction of a [NiCpBr(NHC-cinnamyl)] complex with methyl magnesium bromide and that catalyze effectively the (Z)-selective semihydrogenation of alkynes and ynamides (Scheme 1).…”

“…However, the use of organic solvents represents a large source of waste in the chemical production and is also responsible for the major impact on climate change as analyzed recently by Lipshutz and coworkers. 33 Therefore, chemical reactions performed in water without the use of any other solvent are highly desirable.…”

“…In spite of these significant advances for sustainable chemical reactions, small amounts of organic solvents are often required to help in solubilizing the organic reagents or the catalyst in the micelles. However, the use of organic solvents represents a large source of waste in the chemical production and is also responsible for the major impact on climate change as analyzed recently by Lipshutz and coworkers . Therefore, chemical reactions performed in water without the use of any other solvent are highly desirable.…”

“…In order to prevent such drawbacks and simultaneously direct NP properties, different metal–support interactions and/or the use of organic ligands − have been investigated. In this context, N-heterocyclic carbenes (NHC), which are now privileged ligands in organometallic chemistry and homogeneous catalysis, have been established as valuable stabilization agents for NPs of precious transition metals. − However, this strategy is still at its infancy considering the earth-abundant transition metals, which have been less applied in catalysis and which have become a priority for economical reasons that are not necessarily valid considering climate change and environment . Thus, to the best of our knowledge, there are only five reports on the use of NHC ligands to stabilize Ni NPs and catalyze chemical reactions, such as Kumada couplings, carbonyl hydrosilylations, and alkyne semihydrogenation. − In particular, we have recently reported Ni nanoparticles coordinated to NHC ligands bearing an N-coordinated cinnamyl moiety that are readily prepared by the reduction of a [NiCpBr­(NHC-cinnamyl)] complex with methyl magnesium bromide and that catalyze effectively the ( Z )-selective semihydrogenation of alkynes and ynamides (Scheme ).…”

Graphitic Carbon Nitride as a Photocatalyst for Decarboxylative C(sp2)−C(sp3) Couplings via Nickel Catalysis

“…[2,3] In addition to its lower cost and greater abundance, nickel possesses a different reactivity profile to palladium: displaying a reduced propensity of Ni-alkyl intermediates to undergo β-hydride elimination, and possessing a broader array of accessible oxidation states (0, + 1, + 2, + 3, + 4), meaning that both two-and one-electron redox processes are possible. [4][5][6] These properties mean that nickel is now often the metal of choice for metallaphotoredox C(sp 2 )À C(sp 3 ) bond formation, with seminal examples being reported in 2014 by both Molander, using potassium trifluoroborate salts, and Mac-Millan and Doyle, using carboxylic acids as radical precursors, along with aryl halides, to form new bonds using a dual nickel-iridium catalysed system (Scheme 1A). [7,8] Since then, a wide variety of radical precursors as coupling partners has been reported, expanding the possible synthetic disconnections available for synthetic chemists.…”