Tert-Butylphosphaacetylene

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tert-Butylphosphaacetylene
T-Butylphosphaacetylene.png
TBuCP-from-xtal-3D-balls.png
Names
Preferred IUPAC name
(2,2-Dimethylpropylidyne)phosphane
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/C5H9P/c1-5(2,3)4-6/h1-3H3 X mark.svgN
    Key: PXQNAKPBTIQCTI-UHFFFAOYSA-N X mark.svgN
  • InChI=1/C5H9P/c1-5(2,3)4-6/h1-3H3
    Key: PXQNAKPBTIQCTI-UHFFFAOYAA
  • P#CC(C)(C)C
Properties
C5H9P
Molar mass 100.101 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

tert-Butylphosphaacetylene is an organophosphorus compound. Abbreviated t-BuCP, it was the first example of an isolable phosphaalkyne. Prior to its synthesis, the double bond rule had suggested that elements of Period 3 and higher were unable to form double or triple bonds with lighter main group elements because of weak orbital overlap. The synthesis of t-BuCP discredited much of the double bond rule and opened new studies into the formation of unsaturated phosphorus compounds.

Contents

Synthesis and reactions

The synthesis of t-BuCP entails the reaction of pivaloyl chloride and P(SiMe3)3. The reaction proceeds via the intermediacy of a bis(trimethylsilyl)pivaloylphosphine, which undergoes a 1,3-silyl shift to form E- or Z-phosphoalkene isomers. Carrying out the phosphoalkene reaction at 120-200 °C in the presence of catalytic amounts of solid NaOH forms the final t-BuCP product. [1]

Me3CC(O)Cl + P(SiMe3)3 → Me3CC(O)P(SiMe3)2 + Me3SiCl
Me3CC(O)P(SiMe3)2 → Me3CCP + O(SiMe3)2

Other phosphaalkynes

Phosphaalkynes possessing a C≡P bonded to bulky aryl groups are also known, e.g. Mes*C≡P and P≡C(Tript)C≡P are known to possess C≡P bond lengths of 1.516 and 1.532 Å, respectively (see below). [2] [3] [4] While t-BuCP possesses a carbon-phosphorus bond length of 1.536 Å and a first ionization potential (π MO) of 9.70eV, H-C≡P possesses a C≡P bond length of 1.5421Å and a first ionization potential (π MO) of 10.79eV. [5]

Image center Chem317CPexs Chem317CPexs.png
Image center Chem317CPexs

These physical properties produce characteristic reactivity differences between the two species: tert-butylphosphaacetylene is a stable volatile liquid (b.p. 61 °C), and phosphaacetylene readily reacts to form elemental phosphorus. It has been proposed that isophosphaalkynes (R-P≡C) are produced as intermediates during the syntheses of phosphaalkynes. Such isomeric species have never been isolated.

Reactions

With their characteristic C-P triple bonds, the phosphorus atoms of phosphaalkynes such as tert-butylphosphaacetylene exhibit reactivities similar to nitriles, despite the significant differences between the radii of P (1.09 Å) and N (0.71 Å). At temperatures above 130 °C, the phosphaalkyne undergoes cyclotetramerization. To some extent its reactivity more closely resembles the reactions of alkynes.

tert-Butylphosphaacetylene can bind to metals via various coordination modes to give inorganic and organometallic complexes. These complexes utilize either the triple bond or the nonbonding electrons on P.

Image center Chem317CPbindingformations Chem317CPbindingformations.png
Image center Chem317CPbindingformations

The higher electronegativity of carbon (2.5) over phosphorus (2.2) leads to polarized Cδ−≡Pδ+ bonds, which induces protonation at its carbon center. [6] Its variety of coordination geometries enable tert-butylphosphaacetylene to participate in several types of reactions, including 1,2-additions of halogenated compounds.

Organolithium compounds and enophiles can also react with C-P triple bonds, along with [2+1], [2+2], [2+3], and [2+4] cycloadditions. tert-Butylphosphaacetylene also undergoes a homo Diels-Alder cycloaddition reaction. [7] [8]

Related Research Articles

A carbon–carbon bond is a covalent bond between two carbon atoms. The most common form is the single bond: a bond composed of two electrons, one from each of the two atoms. The carbon–carbon single bond is a sigma bond and is formed between one hybridized orbital from each of the carbon atoms. In ethane, the orbitals are sp3-hybridized orbitals, but single bonds formed between carbon atoms with other hybridizations do occur. In fact, the carbon atoms in the single bond need not be of the same hybridization. Carbon atoms can also form double bonds in compounds called alkenes or triple bonds in compounds called alkynes. A double bond is formed with an sp2-hybridized orbital and a p-orbital that is not involved in the hybridization. A triple bond is formed with an sp-hybridized orbital and two p-orbitals from each atom. The use of the p-orbitals forms a pi bond.

Organolithium reagent

Organolithium reagents are organometallic compounds that contain carbon – lithium bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C-Li bond is highly ionic. Owing to the polar nature of the C-Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

Tetrahedrane Chemical compound

Tetrahedrane is a hypothetical platonic hydrocarbon with chemical formula C4H4 and a tetrahedral structure. The molecule would be subject to considerable angle strain and has not been synthesized as of 2021. However, a number of derivatives have been prepared. In a more general sense, the term tetrahedranes is used to describe a class of molecules and ions with related structure, e.g. white phosphorus.

Organoboron chemistry

Organoborane or organoboron compounds are chemical compounds of boron and carbon that are organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds.

Diphosphene is a type of organophosphorus compound that has a phosphorus-phosphorus double bond, denoted by R-P=P-R'. These compounds are not common but are of theoretical interest. Normally, compounds with the empirical formula RP exist as rings. However, like other multiple bonds between heavy main-group elements, P=P double bonds can be stabilized by a large steric hindrance from the substitutions. The first isolated diphosphene bis(2,4,6-tri-tert-butylphenyl)diphosphene was exemplified by Masaaki Yoshifuji and his coworkers in 1981, in which diphosphene is stabilized by two bulky phenyl group.

Phosphaalkyne

In chemistry, a phosphaalkyne is an organophosphorus compound containing a triple bond between phosphorus and carbon with the general formula R-C≡P. Phosphaalkynes are the heavier congeners of nitriles, though, due to the similar electronegativities of phosphorus and carbon, possess reactivity patterns reminiscent of alkynes. Due to their high reactivity, phosphaalkynes are not found naturally on earth, but the simplest phosphaalkyne, phosphaethyne (H-C≡P) has been observed in the interstellar medium.

A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis. Superbases have been described and used since the 1850s.

Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.

Phosphole is the organic compound with the chemical formula C
4H
4PH; it is the phosphorus analog of pyrrole. The term phosphole also refers to substituted derivatives of the parent heterocycle. These compounds are of theoretical interest but also serve as ligands for transition metals and as precursors to more complex organophosphorus compounds.

Organoaluminium chemistry

Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer triisobutylaluminium, and the titanium-aluminium compound called Tebbe's reagent. The behavior of organoaluminium compounds can be understood in terms of the polarity of the C−Al bond and the high Lewis acidity of the three-coordinated species. Industrially, these compounds are mainly used for the production of polyolefins.

Disilyne Chemical compound

Disilyne is a silicon hydride with the formula Si
2H
2. Several isomers are possible, but none are sufficiently stable to be of practical value. Substituted disilynes contain a formal silicon–silicon triple bond and as such are sometimes written R2Si2 (where R is a substituent group). They are the silicon analogues of alkynes.

Methylidynephosphane (phosphaethyne) is a chemical compound which was the first phosphaalkyne compound discovered, containing the unusual C≡P carbon-phosphorus triple bond.

Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are commercially available and exhibit more convenient reactivity.

Carbene analogs in chemistry are carbenes with the carbon atom replaced by another chemical element. Just as regular carbenes they appear in chemical reactions as reactive intermediates and with special precautions they can be stabilized and isolated as chemical compounds. Carbenes have some practical utility in organic synthesis but carbene analogs are mostly laboratory curiosities only investigated in academia. Carbene analogs are known for elements of group 13, group 14, group 15 and group 16.

Tris(trimethylsilyl)phosphine Chemical compound

Tris(trimethylsilyl)phosphine is the organophosphorus compound with the formula P(SiMe3)3 (Me = methyl). It is a colorless liquid that ignites in air and hydrolyses readily.

Decamethylsilicocene

Decamethylsilicocene, (C5Me5)2Si, is a group 14 sandwich compound. It is an example of a main-group cyclopentadienyl complex; these molecules are related to metallocenes but contain p-block elements as the central atom. It is a colorless, air sensitive solid that sublimes under vacuum.

Trisilaallene

Trisilaallene is a subclass of silene derivatives where a central silicon atom forms double bonds with each of two terminal silicon atoms, with the generic formula R2Si=Si=SiR2. Trisilaallene is a silicon-based analog of an allene, but their chemical properties are markedly different.

Phosphasilene

Phosphasilenes or silylidenephosphanes are a class of compounds with silicon-phosphorus double bonds. Since the electronegativity of phosphorus (2.1) is higher than that of silicon (1.9), the "Si=P" moiety of phosphasilene is polarized. The degree of polarization can be tuned by altering the coordination numbers of the Si and P centers, or by modifying the electronic properties of the substituents. The phosphasilene Si=P double bond is highly reactive, yet with the choice of proper substituents, it can be stabilized via donor-acceptor interaction or by steric congestion.

<i>N</i>-heterocyclic silylene Chemical compound

An N-Heterocyclic Silylene (NHSi) is an uncharged heterocyclic chemical compound consisting of a divalent silicon atom bonded to two nitrogen atoms. The isolation of the first stable NHSi, also the first stable dicoordinate silicon compound, was reported in 1994 by Michael Denk and Robert West three years after Anthony Arduengo first isolated an N-heterocyclic carbene, the lighter congener of NHSis. Since their first isolation, NHSis have been synthesized and studied with both saturated and unsaturated central rings ranging in size from 4 to 6 atoms. The stability of NHSis, especially 6π aromatic unsaturated five-membered examples, make them useful systems to study the structure and reactivity of silylenes and low-valent main group elements in general. Though not used outside of academic settings, complexes containing NHSis are known to be competent catalysts for industrially important reactions. This article focuses on the properties and reactivity of five-membered NHSis.

Allotropes of arsenic

Arsenic in the solid state can be found as gray, black, or yellow allotropes. These various forms feature diverse structural motifs, with yellow arsenic enabling the widest range of reactivity. In particular, reaction of yellow arsenic with main group and transition metal elements results in compounds with wide-ranging structural motifs, with butterfly, sandwich and realgar-type moieties featuring most prominently.

References

  1. ↑ Becker, Gerd; Gresser, Gudrun; Uhl, Werner. "2,2-Dimethylpropylidinphosphan, eine stabile Verbindung mit einem Phosphoratom der Koordinationszahl 1." Zeitschrift für Naturforschung, Teil B:Anorganische Chemie, Organische Chemie 1981, 36, 16.
  2. ↑ Maerkl, Gottfried; Sejpka, Hans. "2-(2,4,6-tri-tert-butylphenyl)-1-phosphaethin, 1,4-bis-(trimethylsiloxy)-1,4-bis-(2,4,6-tri-tert-butylphenyl)-2, 3-diphosphabutadien." Tetrahedron Lett. 1986, 27, 171. doi : 10.1016/S0040-4039(00)83969-6.
  3. ↑ Arif, Atta M.; Barron, Andrew R.; Cowley, Alan H.; Hall, Stephen W. "Reaction of the phospha-alkyne ArCP (Ar = 2,4,6-But 3C6H2) with nucleophiles: a new approach to 1,3-diphosphabutadiene synthesis." J. Chem. Soc., Chem. Commun. 1988, 3, 171. doi : 10.1039/c39880000171.
  4. ↑ Brym, Markus.; Jones, Cameron. "Synthesis, characterisation and reactivity of the first diphosphaalkyne." Dalton Trans. 2003, 19, 3665. doi : 10.1039/b309061b.
  5. ↑ Oberhammer, Heinz; Berker, Gerd; Gresser, Gudrun. "Molecular structures of phosphorus compounds : Part IX. Gas-phase structure of 2,2-dimethylpropylidynephosphine." Journal of Molecular Structure 1981, 75, 283-289. doi : 10.1016/0022-2860(81)85242-8.
  6. ↑ Laali, Kenneth K.; Geissler, Bernhard; Regitz, Manfred; Houser, John J. "C-Protonation of Adamantylphosphaacetylene (1-AdC≡P) and tert-Butylphosphaacetylene (tBuC≡P) in Superacids: Phosphavinyl Cation Generation and Trapping To Form Phosphaalkenes, Formation of Isomeric Boron-Containing Spirocyclic Betaines by Reaction of 1-AdC≡P with B(OTf)3, and Theoretical Studies on Protonation of MeC≡P." J. Org. Chem. 1995, 60, 6362.
  7. ↑ Nixon, John F. "Coordination chemistry of compounds containing phosphorus-carbon multiple bonds." Chem. Rev. 1988, 88, 1327. doi : 10.1021/cr00089a015.
  8. ↑ Regitz, Manfred. "Phosphaalkynes: New Building Blocks in Synthetic Chemistry." Chem. Rev. 1990, 90, 191. doi : 10.1021/cr00099a007.
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