Homogeneous Catalysis. IV. Some Reactions of Silicon Hydrides in the Presence of Cobalt Carbonyls

Abstract

The catalysis of silicon hydride addition t o 1-olefins, catalyzed by dicobalt octacarbonyl, was investigated for triethyl-, triethoxy-, and phenyldichlorosilane. I n all three cases the rate of olefin isomerization exceeded that of olefin hydrosilation. Evidence for the mechanism of the reaction was obtained by examining the reaction of silicon hydrides with dicobalt octacarbonyl. Cobalt hydrocarbonyl and silylcobalt carbonyls were identified as the initial products. The cobalt hydrocarbonyl then decomposes t o hydrogen and dicobalt octacarbonyl or reacts with silicon hydride t o form a silylcobalt carbonyl and hydrogen depending on the concentration and nature of the silicon hydride. I n the presence of olefin it is proposed that alkylcobalt carbonyls are formed from the cobalt hydrocarbonyl, and further reaction with silicon hydrides yields alkylsilanes and regenerates cobalt hydrocarbonyl. No evidence for the participation of silylcobalt carbonyls in the catalytic reaction was found, except for the exchange reaction:Isomerization of deuteriumlabeled terminal olefins was found t o involve intermolecular exchange of deuterium with both C3 + CZ and G -C1 shifts of deuterium. These results are similar to those found earlier for the rhodium chloride trihydrate catalyzed isomerization of olefins and are consistent with the rapid reversible addition of a hydrogen atom or ion to coordinated olefin. Carbon monoxide was found to participate in the reaction of triethylsilane and ethylene to produce unsaturated alkoxysilanes.n previous communications1r2 we reported the use of I dicobalt octacarbonyl as a catalyst for the hydrodation of olefins and the preparation of silylcobalt tetracarbonyls by direct reaction of silicon hydrides with dicobalt octacarbonyl. Since our original communication, the existence of compounds of the type R3Si. CO(CO)~ has received independent confirmation with the synthesis of the parent compound H3Si.Co-(CO)43 and other silylcobalt carbonyl^.^ In this paper we present in detail the preparation and properties of a series of silylcobalt carbonyls and our studies of their role in the cobalt carbonyl catalyzed hydrosilation of olefins, both in the presence and absence of carbon monoxide. Experimental SectionMaterials. Dicobalt octacarbonyl was obtained from Alpha Inorganics as a crystalline solid and as a solution in toluene or heptane. Solutions were analyzed by the method of Sternberg, et al.5The other reagents were purified before use, unless otherwise indicated; the silanes were purified by distillation on a vacuum line, rejecting the first and last quarter of the distillate; olefins were treated by passage through an alumina column to give a product which no longer gave a positive test for hydroperoxide.6Triethylsilane, diphenylsilane, triphenylsilane, trimethylsilane, and trihexylsilane were obtained from Peninsular Chem Research, Inc. Trichlorosilane, phenyldichlorosilane, triethoxysilane, and 1,3,5,7-tetramethylcyclotetrasiloxane were obtained from General Electric Silicone Products Departm...

Catalytic Synthesis of β3‐Amino Acid Derivatives from α‐Amino Acids

“…Related work by Murai and co-workers on the carbonylation of epoxides, [18a] oxetanes, [18b] and benzylic esters [18c] 8 ]. [17,19] Our initial experiments focused on the carbonylation of a representative substrate, 4-ethyl-2-phenyl-2-oxazoline, which proceeded smoothly in 75 % yield using 1 in tetrahydropyran (THP) [Eq. (1)].…”

Post-Functionalization: A Useful Method for the Synthesis of Donor-Func­tionalized N-Heterocyclic Carbene–Transition-Metal Catalysts

“…Cobalt complexes with carbonyl, phosphine, and cyclopentadienyl ligands have long been known to catalyze the hydrosilylation of olefins, but suffer from low catalytic activity, requiring harsh reaction conditions, and promoting side reactions of alkene isomerization and dehydrogenative hydrosilylation. 18 In contrast, the silyl-donor-fuctionalized NHC complexes 12-14 are very active in catalyzing the hydrosilylation of 1-octene with PhSiH 3 with fast initial rates, large turnover number, and high selectivity (Scheme 6). 15 The reaction employing 12 (0.1 mol%) in five minutes can produce n-C 8 H 17 SiPhH 2 and n-C 6 H 13 CHMeSiPhH 2 in 89% total yield with the ratio of 14:1, along with only trace amounts of n-C 8 H 18 (3%) and 2-C 8 H 16 (2%).…”

Formation and multinuclear magnetic resonance investigation of silylammonium tetracarbonylcobaltate contact ion pairs

“…Conductivity measurements have been performed using a Radelkis OK-102/0 type conductivity meter and an electrode of the type K-902 with a cell constant of 0.68 cm −1 (Radelkis). Silylcobalt tetracarbonyls [12,23,38] and N -trimethylsilyl-piperidine [39] were prepared by literature methods. Other amines were commercially available compounds which were dried by standard techniques [40] and distilled before use.…”