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.

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Mononuclear gold(I) acyclic diaminocarbenes (ADCs) were prepared by the reaction of 1,2-cyclohexanediamine with the corresponding isocyanide complexes [AuCl(CNR)] (R = Cy, t Bu). The three-component coupling of aldehydes, amines, and alkynes was investigated by using these gold(I) ADC complexes. The new gold(I) metal complexes are highly efficient catalysts for the synthesis of propargylamines and indolizines in the absence of solvent and in mild conditions. This method affords the corresponding final products with excellent yields in short reaction times. Additionally, chiral gold(I) complexes with ADCs have been prepared and tried in the enantioselective synthesis of propargylamines.

Abstract. We describe a bis-N-heterocyclic carbene Rhodium(III) complex, featuring two trifluoroacetato ligands, that affords a variety of α-vinylsilanes in good yields by hydrosilylation of terminal alkynes. Selectivities around 7:1 α/β-(E) were reached, while the β-(Z) product was only marginally obtained. This example sharply contrasts with the β-(Z)-selectivity observed for its parent diiodido complex Vinylsilanes are valuable building blocks in organic synthesis and, therefore, new preparation methods that would pave the way to a more sustainable production of these compounds are of great interest.[1] Metal-catalyzed hydrosilylation of terminal alkynes is an efficient and atom economical route to vinylsilanes;[2] however, selectivity is a major issue for this reaction as three possible isomers may be obtained. The anti-Markovnikov syn-addition affords the  -(E)-vinylsilane, usually the major reaction product, while the anti-Markovnikov anti-addition gives the less frequent β-(Z)-vinylsilane.[3] On the other hand, Markovnikov additions to obtain selectively α-vinylsilanes are unusual. [3,4] Other noteworthy reports on the preparation of  -vinylsilanes include the hydrosilylation of terminal alkynes directed by hydroxy groups [5] or the silylcupration of terminal alkynes. [6] Although inner-sphere mechanisms seem to explain most of the selectivities hitherto reported, we recently proposed the first ionic outer-sphere mechanism for the hydrosilylation of terminal alkynes, substantiated by DFT calculations. The solvent, namely an acetone molecule, assists the heterolytic splitting of the Si-H bond by catalysts 1a and 1b (Figure 1). [7] Subsequently, the R3Si+ moiety is transferred by means of an oxocarbenium ion ([R3Si-O(CH3)2]+) to the substrate. Finally, nucleophilic attack of the hydrido ligand over the silylation product ([R3Si-C=C-R]+) affords selectively the β-(Z)-vinylsilane as a result of the steric interactions that govern the approach of R3Si-C=C-R+ to the hydrido ligand.

Rhodium complexes featuring one or two trifluoroacetato ligands catalyze the unusual formation of a variety of α‐vinylsilanes in good selectivities by non‐directed hydrosilylation of terminal alkynes.