Cleavage of Si–H and Si–C Bonds by Metal–Ligand Cooperation: Formation of Silyl Anion and Silylene Equivalents from Tertiary Silanes

Abstract

The cleavage of silicon−hydrogen bonds to generate silicon-containing metal complexes has played an essential role in the preparation of organosilicon compounds. Herein, we report the reaction of cyclopentadienone iridium complex 1 with hydrosilanes to afford hydroxycyclopentadienyl iridium silyl complexes 4 via the umpolung of the Si−H bond. The nucleophilicity of the Ir−Si bond in the resulting complex was demonstrated in the reaction with an allyl halide and ethyl acrylate. Furthermore, a silylene complex was formed from hydroxycyclopentadienyl silyliridium complex 4 via the formal reductive elimination of the C−H bond at the silicon center to release benzene. The silylene complex synthesized from tricarbylsilane showed ambiphilic reactivities, which are consistent with the classical reactivities of silylenes.

Piano‐stool dinuclear ruthenium (II) complexes of pyrazine‐carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

“…The bond angle for O(2)-Ru(1)-N(1) of 77.83 (10) in Ru1 is smaller than the bond angle for O(1)-Ru(1)-N (1) of 84.03 (12) in complex Ru3, possibly because of the steric constraints imposed by the quinoline moiety in ligand L3 À (Figures 1 and 2). The bond angles of N(1)-Ru (1)-O(1) 77.83 (10) in Ru1 and 84.03 (12) in Ru3 are within the average bond angle of 78.13 (24) for five related ruthenium (II) complexes containing the η 6 -pcymene spectator ligand. 51 2.3 | Transfer hydrogenation of ketones using Ru (II) catalysts Ru1-Ru4…”

“…This is due to its wide application in the synthesis of many valuable materials, which includes but not limited to fragrances, flavours, agrochemicals and fine‐chemical intermediates as well as pharmaceuticals 1–4 . Indeed, a number of transition metal complexes based on iron, 5 manganese, 6 cobalt, 7 ruthenium, 8 rhodium, 9 vanadium, 10 iridium, 11 nickel 12 and gold 13 have been employed as catalysts in the transfer hydrogenation reactions. Ruthenium (II)‐based catalysts for TH and other transformations have attracted considerable attention because of their efficiency and robustness 14–17 .…”

Reactivity umpolung (reversal) of ligands in transition metal complexes

“…49 where electrophilic attack by polarized dihydrogen on the d 1 silicon of the silylene leads to the dihydride 126 while nucleophilic attack by fluoride from HF leads to the silicon fluoride complex 127 . 142…”

Cyclopentadienone Vanadium(I) Complex: Synthesis, Red/Ox Activity, and Application to Catalytic Transfer Hydrogenation

“…The reactivities of CpO metal complexes are due to the degree of metal-to-CpO electron transfer; it was clarified that introducing an electron-deficient ligand and low-valent metal increased their activities in heterolytic bond cleavage due to the enhanced electron transfer . Accordingly, many research groups applied various low-valent late transition metals, such as Fe 0 , Ir I , , Ni 0 , Pt II , etc., to the red/ox-active metal–ligand cooperative system, which enabled unique elementary reactions and catalytic reactions.…”