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The cyclic alkyl(amino) carbene (cAAC) [:C{N-C6H3(2,6-IPr2)}(CMe2)2CH2] stabilized MeGeGeMe has been isolated in the molecular form with composition (cAAC)MeGe–GeMe(cAAC) (1) at room temperature. Compound 1 was synthesized from the reduction of MeGeCl3 using three equivalents of KC8 in the presence of one equivalent of cAAC. The corresponding silicon compound (cAAC)MeSi–SiMe(cAAC) (2) was also prepared. Compounds 1 and 2 are the first examples of REER compounds (E = Ge, Si) carrying the smallest organic group. Furthermore the structures of compounds 1 and 2 have been investigated by using theoretical methods. The theoretical analysis of the structure of 1 is in agreement with the formation as an unprecedented carbene stabilized bis-germylene whereas compound 2 can be equally described as carbene stabilized bis-silylene with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene. The compounds were also characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Reduction of the neutral carbene tetrachlorosilane adduct (cAAC)SiCl4 (cAAC=cyclic alkyl(amino) carbene :C(CMe2)2(CH2)N(2,6-iPr2C6H3) with potassium graphite produces stable (cAAC)3Si3, a carbene-stabilized triatomic silicon(0) molecule. The Si−Si bond lengths in (cAAC)3Si3 are 2.399(8), 2.369(8) and 2.398(8) Å, which are in the range of Si−Si single bonds. Each trigonal pyramidal silicon atom of the triangular molecule (cAAC)3Si3 possesses a lone pair of electrons. Its bonding, stability, and electron density distributions were studied by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

An elegant general synthesis route for the preparation of two coordinate palladium(0) and platinum(0) complexes was developed by reacting commercially available tetrakis(triphenylphosphine)palladium/platinum with π-accepting cyclic alkyl(amino) carbenes (cAACs). The complexes are characterized by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. The palladium complexes exhibit sharp color changes (crystallochromism) from dark maroon to bright green if the C-Pd-C bond angle is sharpened by approximately 6°, which is chemically feasible by elimination of one lattice THF solvent molecule. The analogous dark orange-colored platinum complexes are more rigid and thus do not show this phenomenon. Additionally, [(cAAC)2Pd/Pt] complexes can be quasi-reversibly oxidized to their corresponding [(cAAC)2Pd/Pt]+ cations, as evidenced by cyclic voltammetry measurements. The bonding and stability are studied by theoretical calculations. [ABSTRACT FROM AUTHOR]

Compound (Me2-cAAC:)2Co0 ( 2; Me2-cAAC:=cyclic (alkyl) amino carbene; :C(CH2)(CMe2)2N-2,6- iPr2C6H3) was synthesized by the reduction of the precursor (Me2-cAAC:)2CoICl ( 1) with KC8 in THF. The cyclic voltammogram of 1 exhibited one-electron reduction, which suggests that synthesis of a bent 2-metallaallene ( 2) from 1 should be possible. Compound 2 contains one cobalt atom in the formal oxidation state zero, which is stabilized by two Me2-cAAC: ligands. Bond lengths from X-ray diffraction are 1.871(2) and 1.877(2) Å with a C-Co-C bond angle of 170.12(8)°. The EPR spectrum of 2 exhibited a broad resonance attributed to the unique quasi-linear structure, which favors near degeneracy and gives rise to very rapid relaxation conditions. The cAACCo bond in 2 can be considered as a typical Dewar-Chatt-Duncanson type of bonding, which in turn retains 2.5 electron pairs on the Co atom as nonbonding electrons. [ABSTRACT FROM AUTHOR]

One and a half decades ago the formation of Si2Cl4 from the intermediate species SiCl2 was theoretically predicted to be exothermic. The hypothetical Si2Cl4 has never been experimentally synthesized and isolated. Herein, we report that the Si2Cl4 species was stabilized as singlet biradical (Cy-cAAC-)2Si2Cl4 utilizing two cAAC (cyclic alkyl(amino) carbene). This compound is stable, isolable, and storable at rt under an inert atmosphere. The electronic structure and bonding were studied by theoretical calculations which revealed that the molecule possesses a singlet biradical ground state with an unpaired electron on each carbene C atom having opposite spin. [ABSTRACT FROM AUTHOR]

A radical change: Cyclic alkyl(amino) carbenes formed zwitterionic adducts with SiCl4, which were further converted into carbon‐centered stable radicals by changing the donor‐acceptor C→Si coordinate bond into a CSi covalent bond through a KC8 reduction. As the carbon radical site was directly bonded to a SiCl3 unit, a radical center that is right next to an acceptor has been generated. [ABSTRACT FROM AUTHOR]

Functionalization of N-heterocyclic carbenes (NHCs) has an important influence on their stability, Lewis donor, and acceptor properties. In this study, we report on the selective functionalization of a four-membered N-heterocyclic bis-silylene (2,6-Ar2C6H3NSi:)2 (1) (Ar = 2,4,6-iPr3C6H2) with mono-oxygen sources N2O and Me3NO. Treatment of 1 with N2O results in the selective formation of mono-silylene (2,6-Ar2C6H3NSi(OH)2)(2,6-Ar2C6H3NSi:) (2) as a major product, along with a small amount of further oxidized product (2,6-Ar2C6H3NSi(OH)2)2 (3). Compound 2 is the first four-membered mono-silylene with a di-coordinate silicon atom. [ABSTRACT FROM AUTHOR]

π ‐ Accepting cyclic alkyl(amino) carbenes (cAACs) react with tetrakis(triphenylphosphine)palladium(0) and the corresponding platinum(0) precursor to form [(cAAC)2Pd] and [(cAAC)2Pt] complexes, with two ‐ coordinate Pd and Pt, respectively, as presented by H. W. Roesky et al. in their Communication on page 9312 ff. The new complexes are characterized by NMR spectroscopy, mass spectrometry and X ‐ ray crystallography. Both Pd and Pt complexes are shown by cyclic voltammetry to undergo reversible one ‐ electron oxidation to produce [(cAAC)2Pd]+ and [(cAAC)2Pt]+. Interestingly, [(cAAC)2Pd] exhibits crystallochromism, changing color from dark maroon to bright green via bending of the C ‐ Pd ‐ C bond angle from 172.75(6)° to 166.94°. [ABSTRACT FROM AUTHOR]

The cyclic alkyl(amino) carbene (cAAC) stabilized biradicals of composition (cAAC)2SiH2 (1), (cAAC)SiMe[sub 2]-SiMe[sub 2](cAAC) (2), and (cAAC)SiMeCl- SiMeCl(cAAC) (3) have been isolated as molecular species. All the compounds are stable at room temperature for more than 6 months under inert conditions in the solid state. All radical species were fully characterized by single- crystal X-ray structure analysis and EPR spectroscopy. Furthermore, the structure and bonding of compounds 1-3 have been investigated by theoretical methods. Compound 1 contains the SiH[sub 2] moiety and this is the first instance, where we have isolated 1 without an acceptor molecule. [ABSTRACT FROM AUTHOR]

Intermediate species dichlorosilylene was generated in situ from trichlorosilane and inserted into the P-Cl bond of diphenylchlorophosphine (Ph2P-Cl) to obtain Ph2P-SiCl3 (1). Monodechlorination of 1 by cyclic alkyl(amino) carbenes (cAACs)/KC8 in THF at low temperature led to the formation of stable radicals Ph2P-Si(cAAC⋅)Cl2 (2a,b). Compounds 2a,b were characterized by X-ray single crystal diffraction, mass spectrometry and studied by cyclic voltammetry and theoretical calculations. Radical properties of 2 are confirmed by EPR measurements that suggest the radical electron in 2 couples with 14N (I = 1), 35/37Cl (I = 3/2), and 31P (I = 1/2) nuclei leading to multiple hyperfine lines. Hyperfine coupling parameters computed from DFT calculations are in good agreement with those of experimental values. Electronic distributions obtained from the theoretical calculations suggest that the radical electron mostly resides on the carbene C of 2. [ABSTRACT FROM AUTHOR]

A disiladicarbene, (Cy-cAAC)2Si2, was synthesized by reduction of Cy-cAAC:SiCl4 adduct with KC8. The dark-colored compound 2 is stable at room temperature for a year under an inert atmosphere. Moreover, it is stable up to 190 °C and also can be characterized by electron ionization mass spectrometry. Theoretical and Raman studies reveal the existence of a Si=Si double bond with a partial double bond between each carbene carbon atom and silicon atom. Cyclic voltammetry suggests that 2 can quasi-reversibly accept an electron to produce a very reactive radical anion, 2•− as an intermediate species. Thus, reduction of 2 with potassium metal at room temperature led to the isolation of an isomeric neutral rearranged product and an anionic dimer of a potassium salt via the formation of 2•−. [ABSTRACT FROM AUTHOR]

Two (cAAC)2Cu complexes, featuring a two-CO Ordinate copper atom in the formal oxidation state zero, were prepared by reducing (Et2-cAAC)2Cu+I- with metallic sodium in THF, and by a one-pot synthesis using Me2-cAAC, Cu(II)Cl2, and KC8 in toluene in a molar ratio of 2:1:2, respectively. Both complexes are highly air and moisture sensitive but can be stored in the solid state for a month at room temperature. DFT calculations showed that in these complexes the copper center has a d10 electronic configuration and the unpaired electron is delocalized over two carbene carbon atoms. This was further confirmed by the EPR spectra, which exhibit multiple hyperfine lines due to the coupling of the unpaired electron with 63/65Cu isotopes, 14N, and 1H nuclei. [ABSTRACT FROM AUTHOR]

Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl2 adduct (1) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound 1 was treated with 2 equiv of KC8 and LiB(sec-Bu)3H to yield a deep blue-colored dicarbene zinc compound (cAAC)2Zn (2) and the colorless hydrogenated zinc compound (cAACH)2Zn (3), respectively. Compounds 2 and 3 were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for 2 which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of 2 in CO2 activation, which yields a zwitterionic cAAC·CO2 adduct. [ABSTRACT FROM AUTHOR]