Christoph Marschner

A New and Easy Route to Polysilanylpotassium Compounds

A method is presented for the synthesis of tertiary, secondary, and primary polysilylpotassium compounds. Reaction of potassium tert-butoxide, in either DME or THF, with a suitable precursor molecule, proceeds by cleavage of a trimethylsilyl− polysilanyl bond, and formation of trimethylsilyl tert-butyl ether and a polysilanylpotassium compound. This route allows easy and flexible access to a number of novel polysilanylpotassium compounds, avoiding the hitherto common use of poisonous mercury compounds.

Coordination Chemistry of Cyclic Disilylated Stannylenes and Plumbylenes to Group 4 Metallocenes

Reduction of group 4 metallocene dichlorides with magnesium in the presence of cyclic disilylated stannylene or plumbylene phosphine adducts yielded the respective metallocene tetrylene phosphine complexes. Under the same conditions the use of the respective dimerized stannylene or plumbylene gave metallocene ditetrylene complexes. A computational analysis of these reactions revealed for all investigated compounds multiple-bonded character for the M–E(II) linkage, which can be rationalized in the case of the monotetrylene complex with the classical σ-donor/π-acceptor interaction. The strength of the M–E(II) bond increases descending group 4 and decreases going from Sn to its heavier congener Pb. The weakness of the Ti–E(II) bonds is caused by the significantly reduced ability of the titanium atom for d–p π-back-bonding.

Dispersion Energy Enforced Dimerization of a Cyclic Disilylated Plumbylene

By reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with PbBr2 in the presence of triethylphosphine a base adduct of a cyclic disilylated plumbylene could be obtained. Phosphine abstraction with B(C6F5)3 led to formation of a base-free plumbylene dimer, which features an unexpected single donor–acceptor PbPb bond. The results of density functional computations at the M06-2X and B3LYP level of theory indicate that the dominating interactions which hold the plumbylene subunits together and which define its actual molecular structure are attracting van der Waals forces between the two large and polarizable plumbylene subunits.

A cyclic disilylated stannylene: synthesis, dimerization, and adduct formation.

Reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with [(Me3Si)2N]2Sn led to the formation of an endocyclic distannene via the dimerization of a transient stannylene. In the presence of strong donor molecules such as PEt3, the stannylene could be trapped as adduct. Reaction of the PEt3 derivative with B(C6F5)3 gave rise to the formation of the stannylene B(C6F5)3 adduct.

The first structurally characterised oligosilylmagnesium compound

Abstract The crystalline magnesium compounds Mg[Si(SiMe3)3]2(thf)2 (1) and MgBr[Si(SiMe3)3](thf)2 (2) are obtained in high yield from MgBr2 and the Li or K sisyl in appropriate stoichiometry in Et2O or thf; NMR spectra and X-ray crystal data for 1 and 2 confirm their structures; for 1: MgSi 2.682(2) A, SiMgSi′ 131.19(15)°.

Seedless growth of sub-10 nm germanium nanowires.

We report the self-seeded growth of highly crystalline Ge nanowires, with a mean diameter as small as 6 nm without the need for a metal catalyst. The nanowires, synthesized using the purpose-built precursor hexakis(trimethylsilyl)digermane, exhibit high aspect ratios (>1000) while maintaining a uniform core diameter along their length. Additionally, the nanowires are encased in an amorphous shell of material derived from the precursor, which acts to passivate their surfaces and isolates the Ge seed particles from which the nanowires grow. The diameter of the nanowires was found to depend on the synthesis temperature employed. Specifically, there is a linear relationship between the inverse radius of the nanowires and the synthesis temperature, which can be explained by a model for the size-dependent melting of simple metals.

Group 4 metallocene complexes of disilenes, digermenes, and a silagermene.

Reactions of 1,2-dipotassiotetrakis(trimethylsilyl)disilane with group 4 metallocene dichlorides lead to the formation of the respective metallocene 1,1,2,2-tetrakis(trimethylsilyl)disilene complexes. While the disilene titanocene complex could be structurally characterized, the zirconocene and hafnocene compounds, which are believed to possess some degree of bis-[bis(trimethylsilyl)silylene] character, can only be isolated in substance as the respective trimethylphosphane adducts. Analogous metallocene 1,1,2,2-tetrakis(trimethylsilyl)digermene complexes and a tetrakis(trimethylsilyl)silagermene complex were prepared. Instead of metallocene 1,1,2,2-tetrakis(trimethylsilyl)distannene complexes, four-membered rings composed of a metallocene and three bis(trimethylsilyl)stannylene units were obtained.

Coordination of non-stabilized germylenes, stannylenes, and plumbylenes to transition metals

Abstract Complexes of transition metals with heavy analogs of carbenes (tetrylenes) as ligands have been studied now for some 40 years. The current review attempts to provide an overview about complexes with non-stabilized (having no π-donating substituents) germylenes, stannylenes, and plumbylenes. Complexes are known for groups 4–11. For groups 6–10 not only examples of monodentate tetrylene ligands, but also of bridging ones are known. While this review covers almost 200 complexes, the field in general has been approached only very selectively and real attempts for systematic studies are very scarce. Although some isolated reports exist which deal with the reactivity of the tetrylene complexes most of the so far published work concentrates on synthesis and characterization.

General synthesis of carbanucleosides via regiospecific epoxide opening by the aglycone

Abstract By reaction of 1,2-anhydro-5- o -acetyl-3- o -benzyl-α- d -carbaxylofuranose 8 with the glycone in alkaline medium followed by deprotection carbanucleosides 10 were obtained.

Coordination Chemistry of Disilylated Germylenes with Group 4 Metallocenes.

Reaction of the PEt3 adduct of a disilylated five-membered cyclic germylene with group 4 metallocene dichlorides in the presence of magnesium led to the formation of the respective germylene metallocene phosphine complexes of titanium, zirconium, and hafnium. Attempts to react the related NHC adduct of a disilylated four-membered cyclic germylene under the same conditions with Cp2TiCl2 did not give the expected germylene NHC titanocene complex. This complex was, however, obtained in the reaction of Cp2Ti(btmsa) with the NHC germylene adduct. A computational analysis of the structure of the group 4 metallocene germylene complexes revealed the multiple-bond character of the M–Ge(II) linkage, which can be rationalized with the classical σ-donor/π-acceptor interaction. The strength of the M–Ge(II) bond increases descending group 4.