Olga A. Gapurenko

Pentagermapyramidane: Crystallizing the “Transition-State” Structure†

The first example of the homonuclear pyramidanes, pentagermapyramidane, was synthesized, fully characterized, and computationally studied to reveal its peculiar structural features and the nature of its apex-to-base bonding interactions. Both solid-state and solution structures of pentagermapyramidane are discussed based on the computed stabilities of its square-pyramidal and distorted forms.

From a Si3-Cyclopropene to a Si3S-Bicyclo[1.1.0]butane to a Si3S-Cyclopropene to a Si3S2-Bicyclo[1.1.0]butane: Back-and-Forth, and In-Between

Compact and highly reactive bicyclo[1.1.0]butanes constitute one of the most fascinating classes of organic compounds. Furthermore, interplay of bicyclo[1.1.0]butanes with their valence isomers, such as buta-1,3-dienes and cyclobutenes, is among the fundamental pericyclic transformations in organic chemistry. Herein we report the back-and-forth interconversion between the cyclotrisilenes and thiatrisilabicyclo[1.1.0]butanes, allowing for the synthesis of novel representatives of such classes of highly reactive organometallics. The peculiar structural and bonding features of the newly synthesized compounds, as well as the mechanism of their isomerization, were verified both experimentally and computationally.

A Cationic Phosphapyramidane

Pyramidanes C[C4 R4 ] constitute a novel class of highly strained and reactive polyhedral clusters that attracted a great deal of attention of both theoreticians and experimentalists. Although well-studied from the theoretical viewpoint, pyramidanes were synthetically inaccessible, and only very recently their very first isolable representatives have been described. In this Communication, we report on the synthesis and structural studies of the cationic pyramidane with the Group 15 element at the apex, namely, phosphapyramidane, an isoelectronic analogue of the neutral pyramidanes of the Group 14 elements.

From Borapyramidane to Borole Dianion

Nonclassical pyramidanes with their inverted tetrahedral configuration of the apical atom are among the most challenging synthetic targets in cluster chemistry. In this Communication, we report on the synthesis and structure of the first representative of pyramidal compounds with the group 13 element at the apex, namely, chloroborapyramidane 2. Reduction of 2 with excess of lithium metal unexpectedly produced the cage-opening product, borole dianion derivative {32-·[Li(thf)+]2}, a 6π-electron aromatic system.

Group 14 element cationic pentagonal–pyramidal complexes Ea[η5-Eb5(SiMe3)5]+ (Ea = Si–Pb, Eb = Si, Ge): A quantum-chemical study

GRAPHICAL ABSTRACT ABSTRACT Heavy 14 group element cationic half-sandwich complexes Ea[η5-Eb5(SiMe3)5]+ (Ea = Si–Pb, Eb = Si, Ge) have been studied at the B3LYP/Def2TZVP level of theory. Structures of the neutral complexes {Si[Si5(SiMe3)5]}+Cl− and {Si[Si5(SiMe3)5]}+[AlCl4]− are also discussed.

Theoretical design of new sandwich compounds of boron, carbon, nitrogen, and oxygen

Energetic and structural characteristics of new sandwich compounds of the second row elements X(Y3)2 and X(Y4)2 (X = B5−, C4−, N3−, O2−, Y = C, Si) stabilized with lithium cations were investigated using the methods of density functional theory B3LYP/6-311+G(d,p) and ab initio MP2(full)/6-311+G(d,p). Carbon sandwich systems were found to be thermodynamically more stable than their silicon analogs. In all systems the formation of hypercoordinated central atom is observed. For the most representative structures the Bader topological analysis of electron density was performed. The key types of distortions in the silicon-containing systems were found.

[2+2] Cycloaddition of the Schrock titanium silylidene and acetylene

Abstract[2+2] Cycloadduct of the titanium silylidene Cp2Ti(thf)=Si[Si3(SiMeBut2)4] and acetylene was readily prepared, isolated, and characterized by NMR spectroscopy and computational studies of the Me3Si-substituted model. Geometric features of the model, based on its optimized geometry, suggest that the best structural description for such [2+2] cycloadduct is a metallacycle rather than a π complex.

Binuclear sandwich and multi-decker sandwich compounds of alkali and alkaline-earth metals: a quantum chemical study

The structures, stabilities, and energy characteristics of simple and multi-decker binuclear sandwich compounds of alkali and alkaline-earth metals with cyclobutadiene, cyclopentadiene, and benzene rings were studied within the framework of the density functional theory by the B3LYP/6-311+G** method. Stable electronic structures of the multi-decker sandwich complexes studied can be formed if the sum of the number of valence electrons of metal atoms and the number of basal-ring π-electrons is 8n – 2, where n is the number of basal rings. Factors responsible for steric and electronic stabilization of such systems as well as co-operative effects associated with changes in the electronic and structural properties of the complexes upon chain extension are analyzed.

Germanium, carbon‐germanium, and silicon‐germanium triangulenes

A series of germanium‐containing triangular molecules have been studied by density functional theory (DFT) calculations. The triangulene topology of the compounds provides for their high‐spin ground states and strong sign alternation of spin density and atomic charge distributions. High values of the exchange coupling constants witness ferromagnetic ordering of electronic structures of all studied triangulenes. The compounds bearing more electronegative atoms in a‐positions of the triangular networks possess higher aromatic character and stronger ferromagnetic ordering.

Arsagermene, a compound with an –AsGe double bond

The first compound featuring an AsGe double bond, arsagermene Mes*AsGe(SiMetBu2)2, was synthesized, isolated and fully characterized. Crystallographic studies revealed that arsagermene has a planar GeAs bond of 2.2731(8) A, which is notably shorter than the standard Ge–As single bond. The double bond character of arsagermene was further supported by computational data.