Catharina Goedecke

A Digermyne with a Ge–Ge Single Bond That Activates Dihydrogen in the Solid State

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 which readily add ammonia, carbon monoxide and other small molecules,

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 σ-donors. They are commonly viewed as workhorses exhibiting reliable, but undramatic, chemical behaviour. The N → Ccarbene π-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(NiPr2)2, adds CO. This reaction affords a β-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.

Low‐Valent Ge2 and Ge4 Species Trapped by N‐Heterocyclic Gallylene

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)).

Spacer Separated Donor–Acceptor Complexes [D→C6F4→BF3] (D = Xe, CO, N2) and the Dication [Xe→C6F4←Xe]2+. A Theoretical Study

Quantum chemical calculations using density functional theory at the BP86/TZ2P+ level and ab initio calculations at MP2/def2-TZVPP have been carried out for the donor-acceptor complexes [D→C(6)F(4)→BF(3)] (D = Xe, CO, N(2),) and the dication [Xe→C(6)F(4)←Xe](2+). The calculations predict rather short D→C(6)F(4)(BF(3)) and (D)C(6)F(4)→BF(3) bonds in the neutral systems which indicate rather strong binding interactions. The calculated partial charges which give large positive values for the donor moieties and negative values for the acceptor fragments and the large bond indices also suggest very strong donor-acceptor interactions D→C(6)F(4)→BF(3) and Xe→C(6)F(4)(2+)←Xe. An energy decomposition analysis suggests very strong intrinsic interactions for both systems. The donor-acceptor bonds in [D→C(6)F(4)→BF(3)] are much stronger than the direct donor-acceptor interactions D→BF(3) which are only weakly bonded van der Waals complexes. The calculated donor-acceptor interactions D→C(6)F(4)(BF(3)) are 26.1 kcal/mol for D = Xe, 121.5 kcal/mol for D = CO, and 86.9 kcal/mol for D = N(2). The strength of the intrinsic (D)C(6)F(4)→BF(3) interactions are calculated to be between 51.1-51.6 kcal/mol. The theoretical bond dissociation energies for the decomposition of [D→C(6)F(4)→BF(3)] yielding D + C(6)F(4) + BF(3) suggests that the xenon compound [Xe→C(6)F(4)→BF(3)] is metastable but may become stabilized in the condensed phase by intermolecular interactions. The complexes [OC→C(6)F(4)→BF(3)] and [N(2)→C(6)F(4)→BF(3)] are predicted to be thermodynamically stable. It is suggested that the above adducts are examples of spacer-separated donor-acceptor complexes [D→S→A] which are a hitherto unrecognized class of molecules.

The Dewar–Chatt–Duncanson model reversed — Bonding analysis of group-10 complexes [(PMe3)2M–EX3] (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl; X = H, F, Cl, Br, I)

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] wit...

Spirobis(pentagerma[1.1.1]propellane): A Stable Tetraradicaloid

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.