Stereodivergent Formation of Alkenylsilanes: syn or anti Hydrosilylation of Alkynes Catalyzed by a Cyclopentadienylcobalt(I) Chelate Bearing a Pendant Phosphane Tether

Abstract

Abstract:The hydrosilylation of alkynes is catalyzed by the di-tert-butylphosphanylethylcyclopentadienylcobalt chelate 1. While the reaction of internal alkynes exclusively affords syn hydrosilylation products with triethylsilane, the reaction with triethoxysilane shows predominant anti stereoselectivity. Reactions of terminal alkynes are less selective with triethylsilane and result in cyclotrimerization when triethoxysilane is used.

[NiX2(NHC)2] Complexes in the Hydrosilylation of Internal Alkynes

“…[35] A cobalt(I) complex was shown to yield 71 % of the (E)-product in 10 h, using 5 mol-% catalyst loading at 40°C. [15] However, using heterogeneous platinum on carbon, the same product could be obtained in 95 % yield in 3 h using only 0.02 mol-% Pt at 80°C. [12] Although the latter catalyst is clearly the most efficient, the nickel catalyst under study may be an attractive alternative as it does not make use of the rather scarce and expensive platinum or rhodium.…”

“…The product was purified by chromatography (silica gel, petroleum ether), and obtained as a colorless oil, which analyzed as (E)-1,4-dimethoxy-2-triethylsilyl-2-butene; [15] yield 219 mg (95 %).…”

“…In general, the hydrosilylation of internal alkynes is less explored than the hydrosilylation of terminal alkynes. [15] Scheme 1. Products in the hydrosilylation of terminal alkynes.…”

“…The hydrosilylation of alkynes may be catalyzed by a number of different metal complexes, including rhodium, [5][6][7] iridium, [6,8] ruthenium [9,10] and platinum. [11][12][13] Complexes of the less precious metals nickel, [14] cobalt, [15] and titanium [16] have also [a] Leiden Institute of Chemistry, Leiden University, P. O. Box 9502, 2300 RA Leiden, The Netherlands Fax: +31-71-5274761 E-mail: bouwman@chem.leidenuniv.nl of the symmetric alkyne 3-hexyne in 60 min at 50°C, with 5 mol-% catalyst loading.…”

A Ligand‐Free Pt3Cluster Catalyzes the Markovnikov Hydrosilylation of Alkynes with up to 106Turnover Frequencies

“…To confirm that the Pt 3 clusters andn oo ther Pt speciesa re catalytically active for the formation of a-vinylsilanes, Pt 3 clusters were synthesized in the form of Chini clusters, including [NEt 4 ] 2 [Pt 3 (CO) 6 ] 3 , [19] Na 2 [Pt 3 (CO) 6 ] 5 , [22] and Na 2 [Pt 3 (CO) 6 ] 10 . [19] These clusters have al ayered structure that only exposes the two terminal Pt 3 units to the reactants, and the CO ligands can exchange with alkynes in < 1min in solution ( Figure S6 in the Supporting Information).…”