Petra Vasko

A germanium isocyanide complex featuring (n → π*) back-bonding and its conversion to a hydride/cyanide product via C-H bond activation under mild conditions.

Reaction of the diarylgermylene Ge(Ar(Me(6)))(2) [Ar(Me(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(CH(3))(3))(2)] with tert-butyl isocyanide gave the Lewis adduct species (Ar(Me(6)))(2)GeCNBu(t), in which the isocyanide ligand displays a decreased C-N stretching frequency consistent with an n → π* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge-C bonding combination between the lone pair of electrons on the germanium atom and the C-N π* orbital of the isocyanide ligand. The complex undergoes facile C-H bond activation to produce a new diarylgermanium hydride/cyanide species and isobutene via heterolytic cleavage of the N-Bu(t) bond.

Addition of Ethylene or Hydrogen to a Main-Group Metal Cluster under Mild Conditions

Reaction of the tin cluster Sn8(Ar(Me6))4(Ar(Me6)=C6H2-2,6-(C6H3-2,4,6-Me3)2) with excess ethylene or dihydrogen at 25 °C/1 atmosphere yielded two new clusters that incorporated ethylene or hydrogen. The reaction with ethylene yielded Sn4(Ar(Me6))4(C2H2)5 that contained five ethylene moieties bridging four aryl substituted tin atoms and one tin-tin bond. Reaction with H2 produced a cyclic tin species of formula (Sn(H)Ar(Me6))4, which could also be synthesized by the reaction of {(Ar(Me6))Sn(μ-Cl)}2 with DIBAL-H. These reactions represent the first instances of direct reactions of isolable main-group clusters with ethylene or hydrogen under mild conditions. The products were characterized in the solid state by X-ray diffraction and IR spectroscopy and in solution by multinuclear NMR and UV/Vis spectroscopies. Density functional theory calculations were performed to explain the reactivity of the cluster.

Mechanistic Study of Stepwise Methylisocyanide Coupling and C–H Activation Mediated by a Low-Valent Main Group Molecule

An experimental and DFT investigation of the mechanism of the coupling of methylisocyanide and C-H activation mediated by the germylene (germanediyl) Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) showed that it proceeded by initial MeNC adduct formation followed by an isomerization involving the migratory insertion of the MeNC carbon into the Ge-C ligand bond. Addition of excess MeNC led to sequential insertions of two further MeNC molecules into the Ge-C bond. The insertion of the third MeNC leads to methylisocyanide methyl group C-H activation to afford an azagermacyclopentadienyl species. The X-ray crystal structures of the 1:1 (Ar(Me6))2GeCNMe adduct, the first and final insertion products (Ar(Me6))GeC(NMe)Ar(Me6) and (Ar(Me6))GeC(NHMe)C(NMe)C(Ar(Me6))NMe were obtained. The DFT calculations on the reaction pathways represent the first detailed mechanistic study of isocyanide oligomerization by a p-block element species.

The Instability of Ni{N(SiMe3)2}2: A Fifty Year Old Transition Metal Silylamide Mystery

The characterization of the unstable Ni(II) bis(silylamide) Ni{N(SiMe3 )2 }2 (1), its THF complex Ni{N(SiMe3 )2 }2 (THF) (2), and the stable bis(pyridine) derivative trans-Ni{N(SiMe3 )2 }2 (py)2 (3), is described. Both 1 and 2 decompose at ca. 25 °C to a tetrameric Ni(I) species, [Ni{N(SiMe3 )2 }]4 (4), also obtainable from LiN(SiMe3 )2 and NiCl2 (DME). Experimental and computational data indicate that the instability of 1 is likely due to ease of reduction of Ni(II) to Ni(I) and the stabilization of 4 through dispersion forces.

CCDC 1519808: Experimental Crystal Structure Determination

Related Article: Petra Vasko, Juha Hurmalainen, Akseli Mansikkamaki, Anssi Peuronen, Aaron Mailman, Heikki M. Tuononen|2017|Dalton Trans.|46|16004|doi:10.1039/C7DT03243A

CCDC 1519804: Experimental Crystal Structure Determination

Related Article: Petra Vasko, Juha Hurmalainen, Akseli Mansikkamaki, Anssi Peuronen, Aaron Mailman, Heikki M. Tuononen|2017|Dalton Trans.|46|16004|doi:10.1039/C7DT03243A

CCDC 1519806: Experimental Crystal Structure Determination

Related Article: Petra Vasko, Juha Hurmalainen, Akseli Mansikkamaki, Anssi Peuronen, Aaron Mailman, Heikki M. Tuononen|2017|Dalton Trans.|46|16004|doi:10.1039/C7DT03243A