Platinum Complexes with Chelating Acyclic Aminocarbene Ligands Work as Catalysts for Hydrosilylation of Alkynes.

ABSTRACT: This work describes the preparation of a series of platinum-aminocarbene complexes [PtCl{C(N=C ^a (C₆R²R³R⁴R⁵CON ^b ))=N(H)R¹}(CNR¹)] ^a-b (8-19, 65-75% isolated yield) via the reaction of cis-[PtCl₂(CNR¹)₂] (R¹ = Cy 1, t-Bu 2, Xyl 3, 2-Cl-6-MeC₆H₃ 4) with 3-iminoisoindolin-1-ones HN=C ^a (C₆R²R³R⁴R⁵CON ^b H) (R²-R⁵ = H 5; R³ = Me, R², R⁴, R⁵ = H 6; R³, R⁴ = Cl, R², R⁵ = H 7). New complexes 17-19 were characterized by elemental analyses (C, H, N), ESI⁺-MS, Fourier transform infrared spectroscopy (FT-IR), one-dimensional (¹H, ¹³C{¹H}), and two-dimensional (¹H,¹H correlation spectroscopy (COSY), ¹H,¹³C heteronuclear multiple quantum correlation (HMQC)/¹H,¹³C heteronuclear single quantum coherence (HSQC), ¹H,¹³C heteronuclear multiple bond correlation (HMBC)) NMR spectroscopy, and authenticity of known species 8-16 was confirmed by FT-IR and ¹H and ¹³C{¹H} NMR. Complexes 8-19 were assessed as catalysts for hydrosilylation of terminal alkynes with hydrosilanes to give vinyl silanes, and complex [PtCl{C(N=C ^a (C₆H₃(5-Me)CON ^b ))=N(H)(2-Cl-6-MeC₆H₃)}{CN(2-Cl-6-MeC₆H₃)}] ^a-b (18) showed the highest catalytic activity. The catalytic system proposed operates at 80-100 °C for 4-6 h in toluene and with catalyst loading of 0.1 mol %, enabling the reaction of a number of terminal alkynes (PhC?CH, t-BuC?CH, and 4-(t-Bu)C₆H₄C?CH) with hydrosilanes (Et₃SiH, Pr₃SiH, i-Pr₃SiH, and PhMe₂SiH). Target vinyl silanes were prepared in 48-95% yields (as a mixture of ?/? isomers) and with maximum turnover number of 8.4 × 10³. Hydrosilylation of internal alkynes (PhC?CPh, Me(CH₂)₂C?C(CH₂)₂Me, and PhC?CMe) with hydrosilanes (Et₃SiH, PhMe₂SiH) led to the corresponding trisubstituted silylated alkenes in 86-94% yields. Initial observations on the mechanism of the catalytic action of platinum-ADC catalysts 8-19 suggested a molecular catalytic cycle.

SUBMITTER: Chay RS 

PROVIDER: S-EPMC6641237 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature