Cobalt(0) and Iron(0) Isocyanides as Catalysts for Alkene Hydrosilylation with Hydrosiloxanes

Abstract

Iron and cobalt isocyanides, Fe(CNR) 5 (1) and Co 2 (CNR) 8 (2), where R = t-butyl ( t Bu), adamantyl (Ad), and mesityl (Mes), were prepared by reduction of FeBr 2 or CoI 2 in the presence of CNR by C 8 K or silica-Na. These complexes were subjected to catalytic hydrosilylation of alkenes with hydrosiloxanes, and the results are compared with those obtained by previously reported Fe(OPiv) 2 /CNAd or Co-(OPiv) 2 /CNAd catalyst systems. Hydrosilylation of allylic ethers with 1,1,1,3,3-pentamethyldisiloxane (PMDS) catalyzed by 1 and the reaction of several alkenes with PMDS or 1,1,1,3,5,5,5-heptamethyltrisiloxane (MD′M) catalyzed by 2 exhibited greater catalytic activity than that observed for the Fe(OPiv) 2 or Co(OPiv) 2 /CNR catalyst system. Complexes 1 and 2 were effective for catalytic chemical modification of silicone fluids containing Si−H groups and for two-component silicone curing. In all cases, selectivity of the reaction in terms of formation of the desired product by hydrosilylation and of byproducts due to dehydrogenative silylation did not differ between the metal isocyanide complexes and the corresponding M(OPiv) 2 /CNR catalyst system. Catalytically active species generated from 1, 2, and the M(OPiv) 2 /CNR catalyst system were also investigated.

Cobalt(II) and (I) Complexes of Diphosphine‐Ketone Ligands: Catalytic Activity in Hydrosilylation Reactions

“…The scope for the unsaturated substrate is versatile, including alkene,, , alkyne, carbonyl, and carboxylic derivative groups. Additionally, a number of different silanes can be used: much research is performed with phenylsilane, and other silanes such as diphenylsilane, alkyl silanes, and alkoxy silanes, can be employed as well.…”

Ni(ii) and Co(ii) bis(acetylacetonato) complexes for alkene/vinylsilane silylation and silicone crosslinking

“…Before quantifying the conversion and the selectivity, the major products of the reaction catalyzed by Ni(tmhd) 2 were identified by NMR spectroscopy. A combination of 1 H, 13 C and 29 Si NMR, as well as GC/GC-MS analyses (for confirmation, in 1-octene case in particular) revealed the major and minor products of the reaction depicted in Fig. 1 for vinylsilane model compounds and 1-octene (see Experimental section and ESI, † sections 1 to 5).…”

“…After the reaction, NMR and and/or GC/GC-MS analyses were performed. 1 H, 13 C and 29 Si NMR spectra were recorded on a Bruker 400 MHz and 700 MHz spectrometers in CDCl 3 and MCH d14. The mass spectra of the products were evaluated by gas chromatography coupled with mass spectrometry (GC-MS) and quantification was determined with gas chromatography (GC) analysis using calibration curves with appropriate substrates.…”

“…Nickel, cobalt and iron catalysts have already been reported and reviewed as relatively active and selective for alkene hydrosilylation (HS) and dehydrogenative silylation (DS). [6][7][8][9][10][11][12][13] Two types of systems have been reported in the literature: low-oxidation state and high-oxidation state complexes. Among low oxidation state catalysts, Chirik's bis(imino) pyridine iron(0) 14 and cobalt(I) 15 are seminal examples, which are very active under strict inert conditions.…”

Earth-Abundant Metal Catalysis Enabled by Counterion Activation

“…24,25 Recently, endogenous (activator free) protocols have been reported using cobalt acetylacetonate complexes to catalyze eneyne cyclisation-borylation 26,27 and alkene diborylation, 28,29 and iron-and cobalt carboxylate complexes to catalyse alkene hydrosilylation. [30][31][32] However, and to the best of our knowledge, only a single example of cobalt-catalysed hydroboration has been reported, 33,34 while endogenous activation for iron-catalysed hydroboration is yet to be realized (Scheme 1B).…”