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

[Image: see text] This work describes the preparation of a series of platinum–aminocarbene complexes [PtCl{C(N=C(a)(C(6)R(2)R(3)R(4)R(5)CON(b)))=N(H)R(1)}(CNR(1))](a–b) (8–19, 65–75% isolated yield) via the reaction of cis-[PtCl(2)(CNR(1))(2)] (R(1) = Cy 1, t-Bu 2, Xyl 3, 2-Cl-6-MeC(6)H(3)4) with 3-iminoisoindolin-1-ones HN=C(a)(C(6)R(2)R(3)R(4)R(5)CON(b)H) (R(2)–R(5) = H 5; R(3) = Me, R(2), R(4), R(5) = H 6; R(3), R(4) = Cl, R(2), R(5) = H 7). New complexes 17–19 were characterized by elemental analyses (C, H, N), ESI(+)-MS, Fourier transform infrared spectroscopy (FT-IR), one-dimensional ((1)H, (13)C{(1)H}), and two-dimensional ((1)H,(1)H correlation spectroscopy (COSY), (1)H,(13)C heteronuclear multiple quantum correlation (HMQC)/(1)H,(13)C heteronuclear single quantum coherence (HSQC), (1)H,(13)C heteronuclear multiple bond correlation (HMBC)) NMR spectroscopy, and authenticity of known species 8–16 was confirmed by FT-IR and (1)H and (13)C{(1)H} 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)(C(6)H(3)(5-Me)CON(b)))=N(H)(2-Cl-6-MeC(6)H(3))}{CN(2-Cl-6-MeC(6)H(3))}](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)C(6)H(4)C≡CH) with hydrosilanes (Et(3)SiH, Pr(3)SiH, i-Pr(3)SiH, and PhMe(2)SiH). Target vinyl silanes were prepared in 48–95% yields (as a mixture of α/β isomers) and with maximum turnover number of 8.4 × 10(3). Hydrosilylation of internal alkynes (PhC≡CPh, Me(CH(2))(2)C≡C(CH(2))(2)Me, and PhC≡CMe) with hydrosilanes (Et(3)SiH, PhMe(2)SiH) 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.