Regioselective hydrosilylation of epoxides catalysed by nickel(ii) hydrido complexes

Abstract

Bench-stable nickel fluoride complexes bearing NNN pincer ligands have been employed as precursors for the regioselective hydrosilylation of epoxides at room temperature. A nickel hydride assisted epoxide opening is followed by the cleavage of the newly formed nickel oxygen bond by σ-bond metathesis with a silane.

Catalytic Reduction of Cyclic Ethers with Hydrosilanes

“…[19] A1 :1 reaction of 3a with styrene oxide resulted in the exclusivef ormation of nickel alkoxide 3b, which could quantitativelyr eact with silanes to regenerate 3a, with the release of ar ing-opening product (Scheme 4). [20] Consistent with such stoichiometric observations, in situ generated 3a was found to catalyze the hydrosilylation of ar ange of styrene oxide derivatives (Scheme 5). The reactiono fs tyrene oxides with as ubstituent at the para positiona nd PhSiH 3 smoothly proceeded at 25 8Ci nt he presence of 3 (5 mol %) to…”

“…Recently, Gade and co‐workers synthesized a nickel(II) fluoride complex with NNN pincer ligand, 3 , which was found to be readily converted into nickel hydrido complex 3 a with hydrosilanes (Scheme ) . A 1:1 reaction of 3 a with styrene oxide resulted in the exclusive formation of nickel alkoxide 3 b , which could quantitatively react with silanes to regenerate 3 a , with the release of a ring‐opening product (Scheme ) . Consistent with such stoichiometric observations, in situ generated 3 a was found to catalyze the hydrosilylation of a range of styrene oxide derivatives (Scheme ).…”

Coordination Chemistry of the PdmBOX Pincer Ligand: Reactivity at the Metal and the Ligand

“…The geometries in both complexes are structurally closely related, and similar to the previously described lithium complex, adopting a distorted tetrahedral coordination (for bond angles see the caption in Figure ). The distortion is also clearly manifested by the strong deviation between the directionality of the pyrrole nitrogen metal bond and the plane of the pyrrole cycle, which is in stark contrast to the previously reported nickel complexes , . As expected for an NNN pincer, the monoanionic pyrrole nitrogen donor features a significantly shorter N–M distance than the corresponding neutral oxazoline nitrogen atoms [2.00 vs. 2.09 Å and 1.96 vs. 2.03 Å for Fe ( 3 ) and Co ( 4 ), respectively], establishing the basis for a robust pincer framework.…”

“…We initially employed these new pincers in the synthesis of nickel compounds, including stable nickel(II) hydride species, for which this structural modification suppressed the previously observed tendency to undergo redox‐transformations to T‐shaped nickel(I) complexes . We have demonstrated that these (PdmBOX)Ni II hydrides cleave strained C–O bonds of epoxides, giving rise to the first nickel‐catalyzed, regioselective hydrosilylation of styrene oxide derivatives to form the corresponding primary alcohols . This catalytic transformation could be realized exclusively with the newly developed spectator ligand since the competition of one‐electron redox steps and the resulting radical transformations were found to be completely suppressed.…”

Alkene hydrosilylation catalyzed by easily assembled Ni(ii)-carboxylate MOFs

“…The ester group (1q and 1r) was compatible. Although nickel-catalyzed ring-opening of epoxide was reported, 60 epoxide was tolerated by this method (1s and 1t). Allylic ether (1u) and allylic amine (1v and 1w) were also suitable substrates.…”