Catalytic competence of silicon, aluminium and phosphorous

This thesis describes the usage of a silicon compound, an aluminium compound and a phosphorous compound in catalysing C-C bond formation and reduction of small molecules.Doctor of Philosoph

Lewis pair polymerization of alkyl methacrylate by amidinato silicon compounds and Tris(pentafluorophenyl)borane

0.5 mol% of the amidinato disilyne [LSi:]2 (1, L = PhC(NtBu)2) and 1 mol% of B(C6F5)3 cooperatively polymerized methyl methacrylate (MMA) to form poly(MMA) with the H and CH2C(=CH2)COMe end groups (P1, Mn = 3.1 ×103 gmol-1; repeating unit, n = 31; polydispersity index, Đ: 1.55). The catalytic mechanism is proposed, where compound 1 could react with MMA and B(C6F5)3 to form a zwitterionic active species [LSi{CH2C(Me)=C(OMe)O}B(C6F5)3]2. The latter could activate MMA molecules affording poly(MMA) chains on the silicon centers. The methyl group of the last enolate of a poly(MMA) chain on a silicon center could then react with the Si-C bond of the adjacent poly(MMA) chain to form P1, as well as regenerate compound 1 and B(C6F5)3. When compound 1 was replaced by the amidinato amidosilylene [LSiN(SiMe3)2] (2), 1 mol% of compound 2 and 1 mol% of B(C6F5)3 mediated living MMA polymerization in toluene to form the poly(MMA) P2 (Mn = 1.04 ×104 gmol-1; Đ: 1.97).National Research Foundation (NRF)Submitted/Accepted versionThis work is supported by the National Research Foundation Singapore NRF-ANR (NRF2018-NRF-ANR026 Si-POP). M.-C. Yang and M.-D. Su are grateful to the National Center for High-Performance Computing of Taiwan for generous amounts of computing time, and the Ministry of Science and Technology of Taiwan for the financial support

Aluminum-Hydride-Catalyzed Hydroboration of Carbon Dioxide

International audienceThis study describes the first use of a bis(phosphoranyl)methanido aluminum hydride, [ClC(PPh 2 NMes) 2 AlH 2 ] (2, Mes = Me 3 C 6 H 2) for the catalytic hydroboration of CO 2. Complex 2 was synthesized by the reaction of a lithium carbenoid [Li(Cl)C(PPh 2 NMes) 2 ] with two equivalents of AlH 3 •NEtMe 2 in toluene at-78 o C. 10 mol % of 2 was able to catalyze the reduction of CO 2 with HBpin in C 6 D 6 at 110 o C for 2 days to afford a mixture of methoxyborane [MeOBpin] (3a; yield: 78 %, TOF: 0.16 h-1) and bis(boryl)oxide [pinBOBpin] (3b). When more potent [BH 3 •SMe 2 ] was used instead of HBpin, the catalytic reaction was extremely pure, resulting in the formation of trimethyl borate [B(OMe) 3 ] (3e) [catalytic loading: 1 mol % (10 mol %); reaction time: 60 min (5 min); yield: 97.6 % (>99 %); TOF: 292.8 h-1 (356.4 h-1)] and B 2 O 3 (3f). Mechanistic studies show that the Al-H bond in complex 2 activated CO 2 to form [ClC(PPh 2 NMes) 2 Al(H){OC(O)H}] (4), which was subsequently reacted with BH 3 •SMe 2 to form 3e and 3f, along with the regeneration of complex 2. Complex 2 also shows good catalytic activity towards hydroboration of carbonyl, nitrile and alkyne derivatives