The cyclic alkyl(amino) carbene stabilized Si2H2 has been isolated in the molecular form of composition (Me-cAAC:)2Si2H2 (1) and (Cy-cAAC:)2Si2H2 (2) at room temperature. Compounds 1 and 2 were synthesized from the reduction of HSiCl3 using 3 equiv of KC8 in the presence of 1 equiv of Me-cAAC: and Cy-cAAC:, respectively. These are the first molecular examples of Si2H2 characterized by single crystal X-ray structural analysis. Moreover, electrospray ionization mass spectrometry and (1)H as well as (29)Si NMR data are reported. Furthermore, the structure of compound 1 has been investigated by theoretical methods. The theoretical analysis of 1 explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene.

The reduction of an N‐heterocyclic carbene (1,3‐diisopropyl‐4,5‐dimethylimidazolin‐2‐ylidene, IiPrMe2 ) adduct of dichloro(ortho‐bromophenyl)borane by tert‐butyl lithium at low temperature yields the IiPrMe2 adduct A of parent benzoborirene, a highly strained boron‐containing bicyclic compound. A is unstable at room temperature and dimerizes at low temperature to the bis‐IiPrMe2 adduct of 9,10‐dihydro‐9,10‐diboraanthracene, characterized by single‐crystal X‐ray crystallography.

Silicon difluoride (SiF ) is highly unstable at room temperature and condenses at this temperature rapidly to a polymeric material of unknown structure. Therefore, the isolation of a stable monomeric silicon difluoride species is a challenging task. The cyclic alkyl(amino) carbene (cAAC) coordinated silicon difluoride was isolated as (cAAC) SiF (2), synthesized from the reduction of cAAC-SiF (1) by using two equivalents of KC in the presence of one equivalent of cAAC. In the solid state, compound 2 is stable at room temperature for a long time under inert conditions. The reduction of compound 1 in the presence of one equivalent KC resulted in the first stable silicon trifluoride monoradical (cAAC)SiF (3).

Reaction of a C2-arylated imidazolium iodide (IPrPh)I (1) (IPrPh = 1,3-bis­(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with PdCl2 in the presence of Ag2O affords abnormal N-heterocyclic carbene (aNHC) palladium complexes (aIPrPh)­PdCl2 (2) and (aIPrPh)2PdCl2 (3) (aIPrPh = 1,3-bis­(2,6-diisopropylphenyl)-2-phenyl-imidazol-4-ylidene). Treatment of 2 with a pyridine gives Pd-PEPPSI-type complexes (aIPrPh)­PdCl2(L) (L = pyridine (py), 5; L = 3-chloropyridine (3Cl-py), 6). Compounds 5 and 6 are also accessible by a one-pot reaction of 1, PdCl2, and Ag2O in a pyridine solvent. While the use of a conventional base K2CO3 leads to the formation of mixed halide complexes (aIPrPh)­Pd­(Cl)­I­(L) (7, L = py; 8, L = 3Cl-py), iodide derivatives (aIPrPh)­PdI2(L) (9, L = py; 10, L = 3Cl-py) can be selectively prepared with addition of an excess of KI to the reaction mixture. Albeit in a low yield, a putative transmetalation agent {(aIPrPh)2Ag}­AgI2 (4) has been isolated and characterized. Compounds 2–10 are air stable crystalline solids and have been characterized by elemental analysis, mass spectrometry, and NMR spectroscopic studies. Molecular structures of 2–10 have been established by single crystal X-ray diffraction analyses. Catalytic activity of three representative compounds 2, 5, and 6 has been tested for the Suzuki-Miyaura cross-coupling reactions.

A convenient new method was added to the toolbox of the ligand design of N-heterocyclic silylenes and their transition-metal complexes. Herein we report on six novel compounds of two novel classes of copper­(I) complexes based on the benzamidinate silylene (Cl)­Si­(PhC­(NtBu)2). By taming the high reactivity of the free electron pair of the Si­(II) atom via a preset metalation with a desired metal precursor (in this case copper­(I) halides) we can easily introduce novel pyridyl-based groups in the subsequent functionalization of the chloro group and undergo coordination of the metal atom at the same time. The resulting pseudocubane-like tetramer [XCu­(I) ← (Cl)­Si­(PhC­(NtBu)2)]4 2a–2c and the trinuclear dimer [(XCu­(I))3­(PyNMes)­Si­(PhC­(NtBu)2)] 3a–3c (with X = Cl (2a/3a), Br (2b/3b), I (2c/3c)) were fully characterized via X-ray diffraction analysis, NMR spectroscopy, mass spectrometry, and elemental analysis. Moreover, we took a look into the catalytic potential of the Cu­(I) complexes 2b and 3b by testing them under the conditions of the renowned copper­(I)-catalyzed alkyne–azide cycloaddition and observed an increased activity of the functionalized species.