Reduction of CO2 by Hydrosilanes in the Presence of Formamidinates of Group 13 and 12 Elements

Weiheng Huang (1) , Thierry Roisnel (1) , Vincent Dorcet (1) , Clement Orione (1) , Evgueni Kirillov (1)

1 ISCR - Institut des Sciences Chimiques de Rennes

Homoleptic complexes 1-M of group 13 and 12 elements (M = B-In and M = Zn, respectively) incorporating electron-withdrawing formamidinate ligands {(C6F5)N=CHN(C6F5)}(-) ({NCN}(-)) were synthesized and isolated in high yields. The compounds were characterized by X-ray crystallography, NMR spectroscopy, and elemental analysis. While the single-component 1-M appeared to be sluggishly active or inactive in the reduction of CO2 with hydrosilanes, a good catalytic performance was achieved with the two-component systems derived from combinations of 1-M and E(C6F5)(3) (E = B, Al). In particular, the binary combination 1-Al/B(C6F5)(3) showed the best performance within the whole series, thus providing quantitative hydrosilane (Et3SiH) conversions under a range of conditions (P-CO2, temperature, benzene or bromobenzene solvent) and affording mainly CH2(OSiEt3)(2) and CH4 as products. Kinetic and mechanistic studies revealed that at the initiation step the binary catalytic systems undergo a complex transformation in the presence of CO2/Et3SiH, affording the products of 1-Al decomposition namely, (C6F5 )N(H)SiEt3, (C6F5)N(Me)SiEt3, {NCN}SiEt3, and also some unidentified aluminum species. Thus, the overall process of the reduction of CO2 with hydrosilanes is presumed to be catalyzed by complex multisite systems, evolved from the formamidinate precursor 1-Al, implicating different tandem combinations of N-base/B(C6F5)(3) with putative Al-containing species.

Domaines: Chimie de coordination; Catalyse

Weiheng Huang, Thierry Roisnel, Vincent Dorcet, Clement Orione, Evgueni Kirillov. Reduction of CO2 by Hydrosilanes in the Presence of Formamidinates of Group 13 and 12 Elements. Organometallics, 2020, 39 (5), pp.698-710. ⟨10.1021/acs.organomet.9b00853⟩. ⟨hal-02531302⟩