Telluropyrylium is an
aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
heterocyclic compound
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
consisting of a six member ring with five carbon atoms, and a positively charged
tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
atom.
Derivatives of telluropyrylium are important in research of infrared dyes.
Naming and numbering
Formerly it was named tellurapyrylium. However this is misleading, as "tellura" indicates that tellurium substitutes for carbon atom, but actually tellurium is substituted for the oxygen atom in
pyrilium
Pyrylium is a cation (positive ion) with formula , consisting of a six-membered ring of five carbon atoms, each with one hydrogen atom, and one positively charged oxygen atom. The bonds in the ring are conjugated as in benzene, giving it an arom ...
.
[ In the Hantzsch-Widman system it is called tellurinium. This is the name used by ]Chemical Abstracts
CAS (formerly Chemical Abstracts Service) is a division of the American Chemical Society. It is a source of chemical information. CAS is located in Columbus, Ohio, United States.
Print periodicals
''Chemical Abstracts'' is a periodical index tha ...
. Replacement nomenclature would call this telluroniabenzene.[
Numbering in telluropyrylium starts with 1 on the tellurium atom and counts up to 6 counter-clockwise on the carbon atoms. The positions adjacent to the chalcogen, numbered 2 and 6 can also be called α, the next two positions 3 and 5 can be termed "β" and the opposite carbon at position 4 can be called "γ".
]
Occurrence
Because telluropyrylium is a positively charged cation, it takes the solid form as a salt with non-nucleophillic anions like perchlorate
A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...
, tetrafluoroborate
Tetrafluoroborate is the anion . This tetrahedral species is isoelectronic with tetrafluoroberyllate (), tetrafluoromethane (CF4), and tetrafluoroammonium () and is valence isoelectronic with many stable and important species including the perchl ...
, or hexafluorophosphate
Hexafluorophosphate is an anion with chemical formula of . It is an octahedral species that imparts no color to its salts. is isoelectronic with sulfur hexafluoride, , and the hexafluorosilicate dianion, , and hexafluoroantimonate . In this anio ...
.
Properties
The positive charge is not confined to the tellurium atom in telluropyrylium, but distributes on the ring in several resonance structures, so that the α and γ positions have some positive charge. A nucleophillic attack targets these carbon atoms.
The shape of the telluropyrylium molecule is not a prefect hexagon, as the bond lengths to the tellurium atom at about 2.068 Å compared to about 1.4 Å for the carbon-carbon bonds. The angle at the tellurium atom is also reduced to about 94°, angles at the α and γ carbon atoms in the ring are about 122° and at the β positions 129°. The whole ring is bent so that it forms a boat shape with an angles of 8.7° on the Te-γ axis. (This was measured in the crystal structure of tetraphenyl telluropyrylium-pyrylium monomethine fluoroborate.
Related
When the ring of telluropyrylium is fused with other aromatic rings larger aromatic structures such as tellurochromenylium, telluroflavylium, and telluroxanthylium result.
See also
*6-membered aromatic rings with one carbon replaced by another group: borabenzene
Borabenzene is a hypothetical organoboron compound with the formula C5H5B. Unlike the related but highly stable benzene molecule, borabenzene would be electron-deficient. Related derivatives are the boratabenzene anions, including the parent 5H5 ...
, silabenzene
A silabenzene is a heteroaromatic compound containing one or more silicon atoms instead of carbon atoms in benzene. A single substitution gives silabenzene proper; additional substitutions give a disilabenzene (3 theoretical isomers), trisilabenz ...
, germabenzene
Germabenzene (C5H6Ge) is the parent representative of a group of chemical compounds containing in their molecular structure a benzene ring with a carbon atom replaced by a germanium atom. Germabenzene itself has been studied theoretically, and syn ...
, stannabenzene
Stannabenzene (C5H6Sn) is the parent representative of a group of organotin compounds that are related to benzene with a carbon atom replaced by a tin atom. Stannabenzene itself has been studied by computational chemistry, but has not been isolat ...
, pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...
, phosphorine
Phosphorine (IUPAC name: phosphinine) is a heavier element analog of pyridine, containing a phosphorus atom instead of an aza- moiety. It is also called phosphabenzene and belongs to the phosphaalkene class. It is a colorless liquid that is m ...
, arsabenzene
Arsabenzene (IUPAC name: arsinine) is an organoarsenic heterocyclic compound with the chemical formula C5H5As. It belongs to a group of compounds called heteroarenes that have the general formula C5H5E (E= N, P, As, Sb, Bi).
This air sensitive li ...
, stibabenzene
Stibinin, also known as stibabenzene, is an organic chemical compound. Stibinin has the chemical formula . The molecule, stibinin, is a derivative of benzene, with one of the carbon atoms in the 6-membered ring replaced by an antimony (Sb) atom. ...
, bismabenzene
Bismabenzene () is the parent representative of a group of organobismuth compounds that are related to benzene with a carbon atom replaced by a bismuth atom. Bismabenzene itself has been synthesised but not isolated because it is too reactive, te ...
, pyrylium
Pyrylium is a cation (positive ion) with formula , consisting of a six-membered ring of five carbon atoms, each with one hydrogen atom, and one positively charged oxygen atom. The bonds in the ring are conjugated as in benzene, giving it an aroma ...
, thiopyrylium
Thiopyrylium is a cation with the chemical formula C5H5S+. It is analogous to the pyrylium cation with the oxygen atom replaced by a sulfur atom.
Thiopyrylium salts are less reactive than the analogous pyrylium salts due to the higher polarizab ...
, selenopyrylium
Selenopyrylium is an aromatic heterocyclic compound consisting of a six-membered ring with five carbon atoms and a positively charged selenium atom.
Naming and numbering
Formerly it was named selenapyrylium. However, this is misleading as "selena ...
References
Extra reading
*{{cite journal, last1=Detty, first1=Michael R., last2=Murray, first2=Bruce J., title=Telluropyrylium dyes. 1. 2,6-Diphenyltelluropyrylium dyes, journal=The Journal of Organic Chemistry, date=December 1982, volume=47, issue=27, pages=5235–5239, doi=10.1021/jo00148a001
Tellurium heterocycles
Heterocyclic compounds with 1 ring
Cations
Six-membered rings