Activation and discovery of earth-abundant metal catalysts using sodium tert-butoxide

First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert-butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2π+2π] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis

Naked (C5Me5)2M Cations (M = Sc, Ti, and V) and Their Fluoroarene Complexes

The ionic metallocene complexes [Cp*2M][BPh4] (Cp* = C5Me5) of the trivalent 3d metals Sc, Ti, and V were synthesized and structurally characterized. For M = Sc, the anion interacts weakly with the metal center through one of the phenyl groups, but for M = Ti and V, the cations are naked. They each contain one strongly distorted Cp* ligand, with one (V) or two (Ti) agostic C-H···M interactions involving the Cp*Me groups. For Sc and Ti, these Lewis acidic species react with fluorobenzene and 1,2-difluorobenzene to yield [Cp*2M(κF-FC6H5)n][BPh4] (M = Sc, n = 2; M = Ti, n = 1) and [Cp*2M(κ2F-1,2-F2C6H4)][BPh4], the first examples of κF-fluorobenzene and κ2F-1,2-difluorobenzene adducts of transition metals. With the perfluorinated anion [B(C6F5)4]-, both Sc and Ti form [Cp*2M(κ2F-C6F5)B(C6F5)3] contact ion pairs. The nature of the metal-fluoroarene interaction was studied by density functional theory (DFT) calculations and by comparison with the corresponding tetrahydrofuran (THF) adducts and was found to be predominantly electrostatic for all metals studied.