Hydrolysis and Methanolysis of Silanes Catalyzed by Iridium(III) Bis-N-Heterocyclic Carbene Complexes: Influence of the Wingtip Groups

Abstract

New [Ir(CH 3 CN) 2 (I) 2 {κC,C′-bis(NHC)}]BF 4 complexes featuring bis-NHC ligands with a methylene bridge and different N substitution (−CH 2 CH 2 CH 2 CH 3 and −CH 2 CH 2 OPh) were synthesized. NMR studies and X-ray diffraction structures evidenced that the wingtip group −CH 2 CH 2 OPh presents a hemilabile behavior in solution, with the oxygen atom coordinating and dissociating at room temperature, which contrasts with the strong coordination of the ether functions in the complex [Ir-(I) 2 {κC,C′,O,O′-bis(NHC OMe )}]BF 4 (bis(NHC OMe ) = methylenebis(N,N′-bis(2-methoxyethyl)imidazol-2-ylidene)), previously reported by us. These complexes proved to be efficient catalysts for the hydrolysis and methanolysis of silanes, affording molecular hydrogen and silyl alcohols or silyl ethers as the main reaction products in excellent yields. The hydrogen generation rates were very much dependent on the nature of the hydrosilane and the coordination ability of the wingtip group. The latter also played a key role in the recyclability of the catalytic system.

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity

“…Furthermore, the C NCN resonance was found at δ 135.4 ppm in the 13 C{ 1 H} NMR spectrum (CD 3 OD), considerably high-field shifted compared to that of 13 (176.2 ppm) in agreement with the oxidation of the iridium center. 22,56,57 The ATR-IR spectrum show an intense absorption at 1694 cm -1 corresponding to the asymmetric stretching COO band of the coordinated carboxylate fragment, at higher energy than in the zwitterionic complex 13 (1648 cm -1 ). which were isolated as dark orange-red solids in good yields (Scheme 6).…”

Ruthenacyclic Carbamoyl Complexes: Highly Efficient Catalysts for Organosilane Hydrolysis

“…That 1a shows significant selectivity for primary silanes (RSiH 3 ) is particularly interesting; the rates are much faster than for the secondary (R 2 SiH 2 ) and tertiary silanes (R 3 SiH), and is probably related to the steric bulk of the organosilane molecule . As mentioned above, although several metal‐based catalysts have been reported for organosilane hydrolysis, none of them displayed such fast rates; this is the first example in which hydrolysis is completed within a few seconds, with a TOF estimated at ~6000 h –1 (Table S2) . Recyclability of the catalyst has been tested for up to five cycles; the yields show an initially slow but steady decline and falls to 68 % by the fifth cycle (Figure S1).…”

Hirshfeld and DFT analysis of the N-heterocyclic carbene proligand methylenebis(N-butylimidazolium) as the acetonitrile-solvated diiodide salt

“…For the preparation of the methylenebis(N-butylimidazolium) cation, [H 2 BisBuIm] 2+ , several pathways have been reported over the years. A general synthetic description could be as follows: a mixture of 1-butylimidazole and CH 2 X 2 [X = Cl (Lee et al, 2008;Lai et al, 2013;Li et al, 2015), Br (Cheng et al, 2010;Zou et al, 2014;Sun et al, 2015) or I (Poyatos et al, 2003;Quezada et al, 2003Quezada et al, , 2004Yang et al, 2008Yang et al, , 2010Mercs et al, 2011;Sun et al, 2011;Aliaga-Lavrijsen et al, 2015)] was stirred in refluxing nonpolar or polar aprotic solvents until a white solid precipitated. This product was then isolated by filtration and washed, giving high yields in all cases.…”

“…We report here the characterization of the bis(imidazolium) salt methylenebis(N-butylimidazolium) diiodide, [H 2 BisBuIm]I 2 , and its isolation as the crystalline material [H 2 BisBuIm]I 2 Á-CH 3 CN, (I), in combination with a Hirshfeld surface analysis and density functional theory (DFT) calculations. Although the [H 2 BisBuIm] 2+ cation has been frequently utilized, its solid-state structure has not been described previously (see, for example, Poyatos et al, 2003;Quezada et al, 2003Quezada et al, , 2004Jin et al, 2005;Lee et al, 2008;Yang et al, 2008Yang et al, , 2010 Lai et al, 2013;Zou et al, 2014;Aliaga-Lavrijsen et al, 2015;Cebollada et al, 2015;Li et al, 2015;Krü ger et al, 2015;Sun et al, 2015).…”