The reduction of the bulky amido-germanium(II) chloride complex, LGeCl (L = N(SiMe(3))(Ar*); Ar* = C(6)H(2)Me{C(H)Ph(2)}(2)-4,2,6), with the magnesium(I) dimer, [{((Mes)Nacnac)Mg}(2)] ((Mes)Nacnac = [(MesNCMe)(2)CH](-); Mes = mesityl), afforded LGeGeL, which represents the first example of a digermyne with a Ge-Ge single bond. Computational studies of the compound have highlighted significant electronic differences between it and multiply bonded digermynes. LGeGeL was shown to cleanly activate H(2) in solution or the solid state, at temperatures as low as -10 °C, to give the mixed valence compound, LGeGe(H)(2)L.

N-Heterocyclic carbenes (NHCs) are extremely valuable as nucleophilic organocatalysts. They are widely applied as ligands in transition-metal catalysed reactions, where they are known as particularly potent s-donors. They are commonly viewed as workhorses exhibiting reliable, but undramatic, chemical behaviour. The N / C carbene p-donation stabilises NHCs at the expense of low reactivity towards nucleophiles. In contrast to NHCs, stable (alkyl)(amino)carbenes exhibit spectacular reactivity, allowing, for example, the splitting of hydrogen and ammonia and the fixation of carbon monoxide. NHCs have been judged to be electronically not suitable for showing similar reactivity. Here, we demonstrate that a ferrocene-based NHC is able to add ammonia, methyl acrylate, tert-butyl isocyanide, and carbon monoxide-reactions typical of (alkyl)(amino)carbenes, but unprecedented for diaminocarbenes. We also show that even the simplest stable diaminocarbene, C(NiPr 2 ) 2 , adds CO. This reaction affords a b-lactam by a subsequent intramolecular process involving a C-H activation. Our results shed new light on the chemistry of diaminocarbenes and offer great potential for synthetic chemistry and catalysis.

Formyl chloride (H(Cl)C=O) is unstable at room temperature and decomposes to HCl and CO. Silicon analogue of formyl chloride, silaformyl chloride IPr·SiH(Cl)=O·B(C(6)F(5))(3) (3) (IPr = 1,3-bis(2,6-diisopropyl-phenyl)imidazol-2-ylidene), was stabilized by Lewis donor-acceptor ligands. Compound 3 is not only the first stable acyclic silacarbonyl compound but also the first silacarbonyl halide reported so far.

Quantum-chemical calculations using DFT and ab initio methods have been carried out for 32 carbenes RR'C which comprise different classes of compounds and the associated ketenes RR'C═C═O. The calculated singlet-triplet gaps ΔE(S-T) of the carbenes exhibit a very high correlation with the bond dissociation energies (BDEs) of the ketenes. An energy decomposition analysis of the RR'C-CO bond using the triplet states of the carbene and CO as interacting fragments supports the assignment of ΔE(S-T) as the dominant factor for the BDE but also shows that the specific interactions of the carbene may sometimes compensate for the S/T gap. The trend of the interaction energy ΔE(int) values is mainly determined by the Pauli repulsion between the carbene and CO. The stability of amino-substituted ketenes strongly depends on the destabilizing conjugation between the nitrogen lone-pair orbital and the ketene double bonds. There is a ketene structure of the unsaturated N-heterocyclic carbene parent compound NHC1 with CO as a local energy minimum on the potential-energy surface. However, the compound NHC1-CO is thermodynamically unstable toward dissociation. The saturated homologue NHC2-CO has only a very small bond dissociation energy of D(e) = 3.2 kcal/mol. The [3]ferrocenophane-type compound FeNHC-CO has a BDE of D(e) = 16.0 kcal/mol.

In this contribution, we report a spirobis(pentagerma[1.1.1]propellane) derivative as a novel type of molecular architecture in cluster chemistry that features two spiro-fused [1.1.1]propellane units and represents a stable tetraradicaloid species. The crucial issue of the nature of the interaction between the germanium bridgeheads was probed computationally, revealing weak bonding interactions between the formally unpaired electrons.

Quantum chemical calculations of the reaction profiles for addition of one and two H 2 molecules to amido-substituted ditetrylynes have been carried using density functional theory at the BP86/def2-TZVPP//BP86/def2-TZVPP level of theory for the model systems L′EEL′ and BP86/def2-TZVPP//BP86/def-SVP for the real compounds. The hydrogenation of the digermyne LGeGeL (L = N(SiMe 3 )Ar*; Ar* = C 6 H 2 Me{C(H)Ph 2 } 2 -4,2,6) follows a stepwise reaction course. The addition of the first H 2 gives the singly bridged species LGe(μ-H)GeHL, which rearranges with very low activation barriers to the symmetrically hydrogenated compound LHGeGeHL and to the most stable isomer LGeGe(H) 2 L, which is experimentally observed. The addition of the second H 2 proceeds with a higher activation energy under rupture of the Ge−Ge bond, yielding LGeH and LGeH 3 as reaction products. Energy calculations which consider dispersion interactions using Grimme's D3 term suggest that the latter reaction is thermodynamically unfavorable. The second hydrogenation reaction LGeGe(H) 2 L → L(H) 2 GeGe(H) 2 L possesses an even higher activation barrier than the bond-breaking hydrogenation step. Further calculations which consider solvent effects change the theoretically predicted reaction profile very little. The calculations of the model system L′GeGeL′ (L′ = NMe 2 ) give a very similar reaction profile. Calculations of the model disilyne and distannyne homologues L′SiSiL′ and L′SnSnL′ suggest that the reactivity of the amido-substituted ditetrylynes always has the order Si > Ge > Sn. The most stable product of the addition of one H 2 to the distannyne L′SnSnL′ is the doubly bridged species L′Sn(μ-H) 2 SnL′, which has been experimentally observed when bulky groups are employed. Analysis of the H 2 − L′EEL′ interactions in the transition state for the addition of the first H 2 with the EDA-NOCV method reveals that the HOMO− LUMO and LUMO−HOMO interactions have similar magnitudes.

Much π and no σ: quantum chemical calculations showed that the Ge atoms of the Ga(2)Ge(2) core in Ge(2)[Ga(DPP)](2) are not bonded by σ interactions, but rather by a transannular π interaction. The compound is formed by reduction of (PCy(3))⋅GeCl(2) with Ga(DDP)/KC(8) which also yielded a further product Ge(4)[Ga(DPP)](2) with a Ge(4) tetrahedron (DDP=HC(CMeNC(6)H(3)-2,6-iPr(2))(2)).

Quantum chemical calculations using BP86 with TZ2P basis sets were carried out to elucidate the structures and the bond–bond dissociation energies of the donor–acceptor complexes [(PMe3)2M–EX3] with X = H, F, Cl, Br, I; E = B, Al, Ga, In, Tl; and M = Ni, Pd, Pt. The nature of the metal–ligand bond was investigated with an energy decomposition analysis. The geometry optimizations gave for most compounds T-shaped structures with nearly linear P–M–P angles where the EX3 ligand has either a staggered or eclipsed conformation with respect to the PMP plane. The energy differences between the conformations are very small which means that there is nearly free rotation about the M–EX3 axis. The equilibrium structures of eight nickel compounds have a distorted geometry where one E–X bond is engaged in attractive interactions with the metal atom which yields a distorted square-planar arrangement of the metal atom. The complex [(PMe3)2Ni–TlI3] exhibits two attractive interactions between Tl–I bonds and the metal which features a five-coordinated metal atom. The calculated bond dissociation energies show that the boron complexes exhibit a different trend for the De values than the heavier group-13 homologues. The results for the Pd and Pt complexes suggest that the [(PMe3)2M–BX3] bond strength increases with F < Cl < Br < I < H which means that the BH3 ligands are the most strongly bonded Lewis acids and BF3 is the most weakly bonded species . The trend for the heavier group-13 complexes [(PMe3)2M–EX3] where E = Al, Ga, In, Tl follows the opposite order F > Cl > Br > I > H. The energy decomposition analysis of the M–EX3 bonds indicates a substantial π contribution of between 12.7% and 30.3% to the total orbital interactions. There is no direct correlation between the strength of the orbital interactions or any of the other energy terms ΔEelstat or ΔEPauli which correlates with the total interaction energy. The bond dissociation energy of the EX3 ligands after breaking the M–EX3 bonds is quite large. It is shown that the intrinsic strength of the M–EX3 bonds is much larger than the BDEs and that the trends of ΔEint and De are not always the same. The EX3 ligands in [(PMe3)2M–BX3] always carry a large negative charge.