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The labile germylene hydride L(Cy)GeH is capable of activating CO2 affording the corresponding formate L(Cy)GeOCH([double bond, length as m-dash]O) (2) (L(Cy) = cyclo-C6H8-1-NAr-2-C(Ph)NAr, Ar = 2,6-iPr2C6H3). Compound and the previously reported LGeOCH([double bond, length as m-dash]O) (L = CH(MeC[double bond, length as m-dash]NAr)2, Ar = 2,6-iPr2C6H3) (2) could be further converted to methanol with the AlH3 · NMe3 alane-amine adduct as a hydrogen source upon workup with water. A plausible mechanism for the conversion of the formate complexes to methanol is proposed based on additional results from the conversion of with the milder hydride delivery agent LAlH2.

Synthesis and characterization of the first manganese(II)-containing heavier thiocarboxylate analogues, [L(Dip)Si(=S)OMnL(Dep)] (4; L(Dip)=CH[C(Me)N(2,6-iPr(2)C(6)H(3))](2), L(Dep)=CH[C(Me)N(2,6-Et(2)C(6)H(3))](2)) and [L(Dip)Ge(=S)OMnL(Dep)] (5) are described. They are accessible through reaction of the silicon and germanium analogues of the respective thiocarboxylic acids [L(Dip)E(=S)OH] (E=Si, Ge) with the β-diketiminato (nacnac) manganese(II) hydride precursor [(L(Dep)Mn)(2)(μ-H)(2)] (3) in high yield. The first Mn nacnac hydride 3 has been prepared by the reaction of manganese bromide [(L(Dep)Mn)(2)(μ-Br)(2)] (2) with KBEt(3)H. Compounds 4 and 5 represent the first transition-metal heavier thiocarboxylates with the Si=S and Ge=S functionalities. All new compounds are paramagnetic and were characterized by elemental analysis, IR spectroscopy, MS (EI), and single-crystal X-ray diffraction analyses. Due to the N→E (E=Si, Ge) and E=S→Mn donor-acceptor interaction as well as the carboxylate-like π-electron delocalization within the E(S)O moieties, the E=S double bonds in these compounds are resonance stabilized., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The isolable ylide-like N-heterocyclic germylene LGe: (2) {L = CH[(C=CH(2))CMe][N(aryl)](2), aryl = 2,6-(i)Pr(2)C(6)H(3)} shows an unprecedented dual reactivity toward terminal alkynes: its reaction with acetylene leads via [4+2] cycloaddition to the novel intramolecular donor stabilised germylene 3, while conversion of phenylacetylene furnishes the analogous cycloadduct 4 along with a C-H bond activation product, the novel N-donor stabilised alkynyl germylene 5.

Monatomic zero-valent silicon and germanium complexes (silylones and germylones), stabilised by neutral donating ligands, emerged only recently as a new class of low-valent group 14 element compounds. Featuring four valence electrons in the form of two lone pairs at a single site, silylones and germylones represent a molecular resting state of single Si and Ge atoms, which are typically only observed at high temperature in the gas phase or in interstellar matter. These species are capable of transferring single Si and Ge atoms to unsaturated substrates and acting as building blocks for novel group 14 species. After introducing this type of compound and the examples known to date, this feature article highlights some chelating bis N-heterocyclic carbene (bis(NHC)) and bis N-heterocyclic silylene (bis(NHSi)) supported Si0 and Ge0 complexes, for which a range of unprecedented reactivity has been discovered. The characteristic behaviour of these silylones and germylones discussed here consists of (i) coordination to Lewis acids, (ii) oxidation with elemental chalcogens, (iii) bond activation of common organic substrates and inert small molecules; and (iv) homocoupling of the Si0 and Ge0 centres. This wealth of reactivity has opened the door to a series of Si and Ge compounds, which would be otherwise difficult to realise. [ABSTRACT FROM AUTHOR]

Using the chelating C,C′‐bis(silylenyl)‐ortho‐dicarborane ligand, 1,2‐(RSi)2‐1,2‐C2B10H10 [R=PhC(NtBu)2], leads to the monoatomic zero‐valent Ge complex ("germylone") 3. The redox non‐innocent character of the carborane scaffold has a drastic influence on the reactivity of 3 towards reductants and oxidants. Reduction of 3 with one molar equivalent of potassium naphthalenide (KC10H8) causes facile oxidation of Ge0 to GeI along with a two‐electron reduction of the C2B10 cluster core and subsequent GeI‐GeI coupling to form the dianionic bis(silylene)‐supported Ge2 complex 4. In contrast, oxidation of 3 with one molar equivalent of [Cp2Fe][B{C6H3(CF3)2}4] as a one‐electron oxidant furnishes the dicationic bis(silylene)‐supported Ge2 complex 5. The Ge0 atom in 3 acts as donor towards GeCl2 to form the trinuclear mixed‐valent Ge0→GeII←Ge0 complex 6, from which dechlorination with KC10H8 affords the neutral Ge2 complex 7 as a diradical species. [ABSTRACT FROM AUTHOR]

A facile, one-pot synthesis of [Na(OC≡As)(dioxane) x] ( x=2.3-3.3) in 78 % yield is reported through the reaction of arsine gas with dimethylcarbonate in the presence of NaO tBu and 1,4-dioxane. It has been employed for the synthesis of the first arsaketenyl-functionalized germylene [LGeAsCO] ( 2, L=CH[CMeN(Dipp)]2; Dipp=2,6- iPr2C6H3) from the reaction with LGeCl ( 1). Upon exposure to ambient light, 2 undergoes CO elimination to form the 1,3-digerma-2,4-diarsacyclobutadiene [L2Ge2As2] ( 3), which contains a symmetric Ge2As2 ring with ylide-like Ge=As bonds. Remarkably, the CO ligand located at the arsenic center of 2 can be exchanged with PPh3 or an N-heterocyclic carbene iPrNHC donor ( iPrNHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to afford the novel germylidenylarsinidene complexes [LGe-AsPPh3] ( 4) and [LGe-As( iPrNHC)] ( 5), respectively, demonstrating transition-metal-like ligand substitution at the arsinidene-like As atom. The formation of 2- 5 and their electronic structures have been studied by DFT calculations. [ABSTRACT FROM AUTHOR]

The first zwitterionic borata-bis(NHC)-stabilized phosphaketenyl germyliumylidene [(L2(O=C=P)Ge:] 2 (L2=( p-tolyl)2B[1-(1-adamantyl)-3-yl-2-ylidene]2) has been synthesized by salt-metathesis reaction of [L2(Cl)Ge:] 1 with sodium phosphaethynolate [(dioxane) nNaOCP]. Unexpectedly, its exposure to UV light affords, after reductive elimination of the entire PCO group, the unprecedented [L2Ge-GeL2] complex 3 in 54 % yields bearing the Ge22+ ion with Ge in the oxidation state +1. In addition, the 1,3-digermylium-2,4-diphosphacyclobutadiene [L2Ge(μ-P)2GeL2] 4 and bis(germyliumylidenyl)-substituted diphosphene [(L2Ge-P=P-GeL2)] 5 could also be obtained in moderate yields. The formation of 3- 5 and their electronic structures have been elucidated with DFT calculations. [ABSTRACT FROM AUTHOR]

The synthesis, reactivity, and electronic structure of the unique germylone iron carbonyl complex [SiNSi]Ge0→Fe(CO)4 is reported. The compound was obtained in 49 % yield from the reaction of the bis(N-heterocyclic silylenyl)pyridine pincer ligand SiNSi (1,6-C5NH3-[EtNSi(NtBu)2CPh]2) with GeCl2⋅(dioxane) to give the corresponding chlorogermyliumylidene chloride precursor [SiNSi]GeIICl+ Cl−, which was further reduced with K2Fe(CO)4. Single-crystal X-ray diffraction analysis of [SiNSi]Ge→Fe(CO)4 revealed that the Ge0 center adopts a trigonal-pyramidal geometry with a Si-Ge-Si angle of 95.66(2)°. Remarkably, one of the SiII donor atoms in the complex is five-coordinated because of additional (pyridine)N→Si coordination. Unexpectedly, the reaction of [SiNSi]Ge→Fe(CO)4 with GeCl2⋅(dioxane) (one molar equivalent) yielded the first push-pull germylone-germylene donor-acceptor complex, [SiNSi]Ge→GeCl2→Fe(CO)4 through the insertion of GeCl2 into the dative Ge0→Fe bond. The electronic features of the new compounds were investigated by DFT calculations. [ABSTRACT FROM AUTHOR]

The unexpected isomerization of the potassium bis(N-heterocyclic carbene)borate [BPh2( tBuNHC)2]K ( 2′) ( tBuNHC = 3- tert-butylimidazole-2-ylidene) in toluene, affording the unique potassium imidazolyl-NHC-borate [BPh2( tBuIm)( tBuNHC)]K ( 2) ( tBuIm = 3- tert-butyl-2-imidazolyl), is reported. The latter crystallizes as the centrosymmetric dimer 22. According to the results of DFT calculations, the rearrangement of 2′ is basically triggered by the solvation of the K+ ion: while 2′ is most stable in THF solutions, the formation of 2 is feasible in least coordinating toluene and drastically favored through dimerization to give 22. The latter reacts with GeCl2 ·dioxane to form solely the unprecedented chlorogermyliumylideneborate [BPh2( tBuIm)( tBuNHC)]GeCl ( 3). Treatment of 3 with KHB( sBu)3 furnishes the corresponding hydridogermyliumylideneborate complex [BPh2( tBuIm)( tBuNHC)]GeH ( 4) in 66 % yield. [ABSTRACT FROM AUTHOR]

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In contrast to the well-established chemistry of ketones (R2CO), the reactivity of the elusive heavier congeners R2EO (E=Si, Ge, Sn, Pb) is far less explored because of the high polarity of the EO bonds and hence their tendency to oligomerize with no activation barrier. Very recently, great advances have been achieved in the synthesis of isolable compounds with EO bonds, including the investigation of donor-stabilized isolable silanones and the first stable 'genuine' germanone. These compounds show drastically different reactivities compared to ketones and represent versatile building blocks in silicon-oxygen and germanium-oxygen chemistry. This and other exciting achievements are described in this Minireview. [ABSTRACT FROM AUTHOR]

Modifying the β-diketimine ligand LH 1 (LH=[ArNC(Me)CHC(Me)NHAr], Ar=2,6- iPr2C6H3) through replacement of the proton in 3-position by a benzyl group (Bz) leads to the new BzLH ligand 2, which could be isolated in 77 % yield. According to 1H NMR spectroscopy, 2 is a mixture of the bis(imino) form [(ArNC(Me)]2CH(Bz) 2a and its tautomer [ArNC(Me)C(Bz)C(Me)NHAr] 2b. Nevertheless, lithiation of the mixture of 2a and 2b affords solely the N-lithiated β-diketiminate [ArNC(Me)C(Bz)C(Me)NLiAr], BzLLi 3. The latter reacts readily with GeCl2⋅dioxane to form the chlorogermylene BzLGeCl 4, which serves as a precursor for a new zwitterionic germylene by dehydrochlorination with LiN(SiMe3)2. This reaction leads to the zwitterionic germylene BzL′Ge: 5 (BzL′=ArNC(CH2)C(Bz)C(Me)NAr) which could be isolated in 83 % yield. The benzyl group has a distinct influence on the reactivity of zwitterionic 5 in comparison to its benzyl-free analogue, as shown by the reaction of 5 with phenylacetylene, which yields solely the 1,4-addition product 6, that is, the alkynyl germylene BzLGeCCPh. Compounds 2- 6 have been fully characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of the first manganese(II)-containing heavier thiocarboxylate analogues, [LDipSi(S)OMnLDep] ( 4; LDip=CH[C(Me)N(2,6- iPr2C6H3)]2, LDep=CH[C(Me)N(2,6-Et2C6H3)]2) and [LDipGe(S)OMnLDep] ( 5) are described. They are accessible through reaction of the silicon and germanium analogues of the respective thiocarboxylic acids [LDipE(S)OH] (E=Si, Ge) with the β-diketiminato (nacnac) manganese(II) hydride precursor [(LDepMn)2(μ-H)2] ( 3) in high yield. The first Mn nacnac hydride 3 has been prepared by the reaction of manganese bromide [(LDepMn)2(μ-Br)2] ( 2) with KBEt3H. Compounds 4 and 5 represent the first transition-metal heavier thiocarboxylates with the SiS and GeS functionalities. All new compounds are paramagnetic and were characterized by elemental analysis, IR spectroscopy, MS (EI), and single-crystal X-ray diffraction analyses. Due to the N→E (E=Si, Ge) and E=S→Mn donor-acceptor interaction as well as the carboxylate-like π-electron delocalization within the E(S)O moieties, the ES double bonds in these compounds are resonance stabilized. [ABSTRACT FROM AUTHOR]

Starting from the chlorogermyliumylidene chloride salt [L(Cl)Ge:]Cl (1) (L = 1,1′-methylene-3,3′-di-2,6-diisopropyl-phenylimidazole-2,2′-diylidene), the chloride ion can be easily substituted by BPh4 to yield [L(Cl)Ge:]BPh4 (3). Reaction of the latter with NaN3 furnishes [L(N3)Ge:]BPh4 (4). In contrast, the direct reaction of 1 with NaN3 affords exclusively the first azidogermyliumylidene azide salt [L(N3)Ge:]N3 (2). The latter represents the first isolable diazido Ge(ii) complex with a covalently bonded azido ligand and a weakly coordinating azide anion as the counterion. All new compounds 2, 3, and 4 were fully characterized, including using X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Conspectus Monoatomic zerovalent main-group element complexes emerged very recently and attracted increasing attention of both theoretical and experimental chemists. In particular, zerovalent silicon complexes and their congeners (metallylones) stabilized by neutral Lewis donors are of significant importance not only because of their intriguing electronic structure but also because they can serve as useful building blocks for novel chemical species. Featuring four valence electrons as two lone pairs at the central atoms, such complexes may form donor-acceptor adducts with Lewis acids. More interestingly, with the central atoms in the oxidation state of zero, they could pave a way to new classes of compounds and functional groups that are otherwise difficult to realize. In this Account, we mainly describe our contributions in the chemistry of monatomic zerovalent silicon (silylone) and germanium (germylone) supported by a chelate bis-N-heterocyclic carbene (bis-NHC) ligand in the context of related species developed by other groups in the meantime. Utilizing the bis-NHC stabilized chlorosilyliumylidene [:SiCl]+ and chlorogermyliumylidene [:GeCl]+ as suitable starting materials, we successfully isolated silylone (bis-NHC)Si and germylone (bis-NHC)Ge, respectively. The electronic structures of the latter complexes established by theoretical calculations and spectroscopic data revealed that they are genuine metallylone species with electron-rich silicon(0) and germanium(0) centers. Accordingly, they can react with 1 molar equiv of GaCl3 to form Lewis adducts (bis-NHC)E(GaCl3) (E = Si, Ge) and with 2 molar equiv of ZnCl2 to furnish (bis-NHC)Si(ZnCl2)2. Conversion of the metallylones with elemental chalcogens affords isolable monomeric silicon(II) and germanium(II) monochalcogenides (bis-NHC)EX(GaCl3) (X = Se, Te), representing molecular heavier congeners of CO. Moreover, their reaction with elemental chalcogens can also yield monomeric silicon(IV) and germanium(IV) dichalcogenides (bis-NHC)EX2 (X = S, Se, Te) as the first isolable complexes of the molecular congeners of CO2. Moreover, (bis-NHC)Si could even activate CO2 to afford the monomolecular silicon dicarbonate complex (bis-NHC)Si(CO3)2 via the formation of SiO and SiO2 complexes as intermediates. Furthermore, starting with a chelate bis-N-heterocyclic silylene supported [:GeCl]+, we developed two bis-N-heterocyclic silylene stabilized germylone→Fe(CO)4 complexes. Our achievements in the chemistry of metallylones demonstrate that the characteristic of monatomic zerovalent silicon and its analogues can provide novel reaction patterns for access to unprecedented species and even extends the series of functional groups of these elements. With this, we can envision that more interesting zerovalent complexes of the main-group elements with unprecedented reactivity will follow in the near future. [ABSTRACT FROM AUTHOR]

Stoichiometric reduction of the bulky β-diketiminato germanium(II) chloride complex [(ButNacnac)GeCl] (ButNacnac = [{N(Dip)C(But)}2CH]-, Dip = C6H3Pri2-2,6) with either sodium naphthalenide or the magnesium(I) dimer [{(MesNacnac)Mg}2] (MesNacnac = [(MesNCMe)2CH]-, Mes = mesityl) afforded the radical complex [(ButNacnac)Ge:]• in moderate yields. X-ray crystallographic, EPR/ENDOR spectroscopic, computational, and reactivity studies revealed this to be the first authenticated monomeric, neutral germanium(I) radical. [ABSTRACT FROM AUTHOR]

The article examines the synthesis of new types of cyclopentadienides (Cp) analogues containing divalent group 14 elements, which may lead to electron-rich transition metal complexes with unusually high reduction potential, owing to the presence of strong electropositive low-valent group 14 metals. According to the authors, to their knowledge, no Cp analogues containing low-valent heavier group 14 elements are known as yet.