Tetrahedrane

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Tetrahedrane

Tetrahedrane is a platonic hydrocarbon with chemical formula

Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
₄₄ and a tetrahedral

Tetrahedron

A tetrahedron is a polyhedron composed of four triangle faces, three of which meet at each vertex . A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids....
structure. Extreme angle strain

Angle strain

The presence of angle strain in a molecule indicates that in a specific chemical conformation there exist bond angles that deviate from the ideal bond angles required to achieve maximum bond strength....
(carbon bond angles deviate considerably from the tetrahedral bond angle of 109.5°) prevents this molecule from forming outside of man-made production.

In 1978, Günther Maier prepared a stable tetrahedrane with four tert-butyl substituent

Substituent

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Encyclopedia

Tetrahedrane is a platonic hydrocarbon with chemical formula

Chemical formula

Tetrahedron

Angle strain

Substituent

In organic chemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. The suffix -yl is used when naming organic compounds that contain a substituent....
s. These substituents are very bulky, and completely envelop the tetrahedrane core. Bonds in the core are prevented from breaking because this would force the substituents closer together (corset effect) resulting in Van der Waals strain

Van der Waals strain

In chemistry, van der Waals strain is strain resulting from van der Waals force repulsion when two substituents in a molecule approach each other with a distance less than the sum of their Van der Waals radius....
. Tetrahedrane is one of the possible platonic hydrocarbons

Platonic hydrocarbons

Platonic hydrocarbons are the molecule representation of platonic solid geometries with vertices replaced by carbon atoms and with edges replaced by chemical bonds....
and has the IUPAC name tricyclo[1.1.0.0^2,4]butane.

Tetra(trimethylsilyl)tetrahedrane

In Tetra(trimethylsilyl)tetrahedrane (I) the tert-butyl groups have been replaced by trimethylsilyl

Trimethylsilyl

Covalent bond

A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds....
is longer than a carbon-carbon bond, and therefore the corset effect is reduced. On the other hand, the trimethylsilyl group is a sigma donor

Sigma bond

In chemistry, sigma bonds are the strongest type of covalent bond chemical bond. Sigma bonding is most clearly defined for diatomic molecules using the language and tools of symmetry groups....
which explains the increased stabilization of the tetrahedrane. Whereas the tert-butyl tetrahedrane melts at 135 °C, at which temperature decomposition to the cyclobutadiene starts, the trimethyl silyl tetrahedrane melts at a much higher temperature of 202 °C, and is stable up to 300 °C, at which point it reverts to the acetylene

Acetylene

Acetylene is the chemical compound with the symbol carbonhydrogen. It is the simplest alkyne.As an alkyne, acetylene is Saturation because its two carbon atoms are Chemical bond together in a triple bond....
starting material.

The tetrahedrane skeleton is made up of banana bond

Banana bond

Bent bond, also known as banana bond, is a term in organic chemistry that refers to a type of covalent bond chemical bond with a geometry somewhat reminiscent of a banana....
s, and hence the carbon atoms are high in s-orbital character. From NMR

NMR spectroscopy

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei....
, sp hybridization can be deduced, normally reserved for triple bonds. As a consequence the bond length

Bond length

In molecular geometry, bond length or bond distance is the average distance between nuclei of two chemical bond atoms in a molecule....
s are unusually short with 1.52 angstroms (152 picometers). The latest development is the organic synthesis

Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
and characterization of the tetrahedrane dimer (II). The connecting bond is even shorter with 1.436 Å (143.6 pm). An ordinary carbon carbon bond has a length of 1.54 Å (154 pm).

Tetrasilatetrahedrane

In tetrasilatetrahedrane the carbon atoms in the tetrahedrane cage are replaced by silicon

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
. The standard silicon silicon bond is much longer (235 pm) and the cage is again enveloped by a total of 16 trimethylsilyl

Trimethylsilyl

A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule....
groups. This makes the compound thermally stable. The silatetrahedrane can be reduced with potassium graphite to the tetrasilatetrahedranide potassium salt. In this compound one of the silicon atoms of the cage has lost a silyl substituent and carries a negative charge. The potassium cation can be captured by a crown ether

Crown ether

Crown ethers are heterocycle chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., -CH2CH2O-....
and in the resulting complex potassium and the silyl anion are separated by a distance of 885 picometer. One of the Si^- - Si bonds is now 272 picometer and its silicon atom has an inverted tetrahedral geometry. Furthermore the four cage silicon atoms are equivalent on the NMR

NMR

NMR may refer to:Applications of Nuclear Magnetic Resonance:* Nuclear Magnetic Resonance.* NMR Spectroscopy.* Proton NMR.* Carbon-13 NMR....
timescale due to migrations of the silyl substituents over the cage.

The dimerization reaction observed for the carbon tetrahedrane compound is also attempted for a tetrasilatetrahedrane. In this tetrahedrane the cage is protected by 4 so-called super silyl groups in which a silicon atom has 3 tert-butyl substituents. The dimer does not materialize but a reaction with iodine

Iodine

Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
in benzene followed by reaction with the tri-tert-butyl sila anion results in the formation of an eight membered silicon cluster compound which can be described as a Si₂ dumbbell (length 229 picometer and with inversion of tetrahedral geometry) sandwiched between two almost parallel Si₃ rings.

In known eight-membered clusters of in the same carbon group

Carbon group

The carbon group is group 14 in the periodic table. Once also known as the tetrels , stemming from the earlier naming convention of this group as Group IVA....
, tin

Tin

Tin is a chemical element with the symbol Sn and atomic number 50. Tin is obtained chiefly from the mineral cassiterite, where it occurs as an oxide, SnO2....
Sn₈R₆ and germanium

Germanium

Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, greyish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon....
Ge₈R₆ the cluster atoms are located on the corners of a cube.