The terminal zinc hydride complex [Tntm]ZnH (2; Tntm=tris(6-tert-butyl-3-thiopyridazinyl)methanide) is an efficient hydrosilylation catalyst of CO at room temperature without the need of Lewis acidic additives. The inherent electrophilicity of the system leads to selective formation of the monosilylated product (MeO) SiO CH (at room temperature with a TOF of 22.2 h and at 45 °C with a TOF of 66.7 h ). In absence of silanes, the intermediate formate complex [Tntm]Zn(O CH) (3) is quantitatively formed within 5 min. All complexes were fully characterized by H and C NMR spectroscopy and single-crystal X-ray diffraction analyses. Density functional theory (DFT) calculations reveal a high positive charge on zinc and the increased preference of the ligand to adopt a κ -coordination mode.

The terminal zinc hydride complex [Tntm]ZnH (2; Tntm = tris(6-tert-butyl-3-thiopyridazinyl)methanide) is an efficient hydrosilylation catalyst of CO 2 at room temperature without the need of Lewis acidic additives.T he inherent electrophilicity of the system leads to selective formation of the monosilylated product (MeO) 3 SiO 2 CH (at room temperature with aTOF of 22.2 h À1 and at 45 8 8Cwith aTOF of 66.7 h À1 ). In absence of silanes,t he intermediate formate complex [Tntm]Zn(O 2 CH) (3)i sq uantitatively formed within 5min. All complexes were fully characterized by 1 Ha nd 13 CNMR spectroscopya nd single-crystal X-rayd iffraction analyses. Density functional theory (DFT) calculations reveal ah igh positive charge on zinc and the increased preference of the ligand to adopt a k 3 -coordination mode.The use of carbon dioxide as substrate for catalytic transformations has received considerable attention not only because of environmental aspects,b ut also because it is ac heap and potentially useful C 1 feedstock. [1] Reduction to the formic acid level is of particular interest, because it can also be used as fuel. [2] Furthermore,o wing to its excellent potential as H 2 carrier,the demand of formic acid is expected to increase in the near future. [3] Thecatalytic reduction of CO 2 with silanes is well-known, mainly using ruthenium complexes with ac ombination of high CO 2 pressures (20-80 bar) and moderate to high temperatures (45-100 8 8C), [4] but also Cu, [5] Ir, [6] and Pd [7] complexes were found to catalyze this reaction under mild conditions.In terms of price,a bundance,a nd toxicity of the metal center, the use of zinc-based systems is of significant interest. Thus,it is surprising that only very few examples of zinc-catalyzed hydrosilylation of CO 2 have been reported:t wo cationic,Nheterocyclic carbene (NHC) stabilized zinc complexes,ad icationic NHC-stabilized zinc hydride cluster,a swell as the tris(thiopyridyl)methane based [Tptm]ZnH and the tris[(1isopropylbenzimidazol-2-yl)dimethylsilyl]methane based [Tism PriBenz ]ZnH complexes were shown to catalytically react with CO 2 in presence of silanes (Figure 1). [8][9][10][11][12] However,these systems require either high temperatures and high pressures or only show low to moderate turnover numbers and turnover frequencies.O nly the recently introduced [Tism PriBenz ]b ased system was found to catalyze the hydrosilylation of CO 2 under ambient conditions,albeit with the use of ab orane additive and with only low turnover frequencies. [11] Herein we show that the recently introduced [Tntm] system [13] allows the isolation of the terminal zinc hydride complex [Tntm]ZnH. Compared to the similar [Tptm]ZnH complex, the more electron deficient thiopyridazine heterocycles were expected to render the metal center more Lewis acidic and thus more reactive (Figure 1). Indeed, we found [Tntm]ZnH to catalytically reduce CO 2 with trimethoxysilane at room temperature and under mild conditions.T his is the first zinc-based system capable of catalytically reducing CO...