The selective semihydrogenation of alkynes to (E)-alkenes is a challenging transformation that is of significant synthetic interest. The development of direct hydrogenation catalysts for this transformation that are based on earth-abundant 3d transition metals and are tolerant of diverse functional groups is highly sought after. We report herein that the bis­(phosphino)­silyl Ni hydride complex ( i Pr-PSiPInd)­NiH (1) is an effective pre-catalyst for the (E)-selective semihydrogenation of a broad range of diaryl alkynes and SiMe3-protected terminal alkynes. Complex 1 exhibits this reactivity under mild conditions (1 atm H2, 25–50 °C, and 1–2.5 mol % Ni) to afford the corresponding (E)-alkenes with high selectivity. Stoichiometric experiments reveal that facile alkyne insertion and subsequent alkene isomerization lead to the observed selectivity.

The synthesis and structural characterization of low‐coordinate Fe(II) and Co(II) complexes supported by the monoanionic P,N‐ligand N‐(2‐dicyclohexylphosphinophenyl)‐2,6‐diisopropylanilide are described. A three‐coordinate (P,N)Fe‐hexamethyldisilazide complex (2), and four‐coordinate (P,N)Fe‐ (3‐Fe) and (P,N)Co‐alkyl (3‐Co) complexes were evaluated as pre‐catalysts for the hydrosilylative reduction of amides with PhSiH3 (5 mol % pre‐catalyst, 1 equiv. PhSiH3, 80 °C, 1–24 h). The Fe complex 2 proved to be more broadly effective for the reduction of a variety of tertiary amide substrates, and was shown to mediate the reduction of N,N‐dibenzylbenzamide at a loading of 1 mol %, to achieve near quantitative formation of tribenzylamine in 1 h (80 °C). Complex 2 also proved effective for the hydrosilylation of tertiary amides under ambient conditions (5 mol % Fe, 24 h), which is a unique example of room temperature amide hydrosilylation mediated by an Fe catalyst without the need for photochemical activation. Given the widespread use of amide reduction protocols in synthesis, the development of efficient Fe‐based catalysts that operate under mild conditions is an important target.

The Cover Feature depicts a three‐coordinate (P,N)Fe‐hexamethyldisilazide complex that functions as an effective pre‐catalyst for the hydrosilylative reduction of tertiary amides to amines using phenylsilane as the reductant. In their Full Paper, Laura Turculet and co‐workers detail the synthesis of this complex and related Fe and Co alkyl derivatives, and explore the scope of amide hydrosilylation catalysis mediated by such 3d‐metal species. Rare examples of room temperature reactivity in the absence of photochemical activation involving the Fe‐hexamethyldisilazide pre‐catalyst (5 mol% Fe, 24 h) are reported. More information can be found in the Full Paper by Dylan J. Hale et al. on page 3818 in Issue 16, 2019 (DOI: 10.1002/cctc.201900550).