Organobismuth chemistry is the chemistry of organometallic compounds containing a carbon to bismuth chemical bond. Applications are few. [1] [2] The main bismuth oxidation states are Bi(III) and Bi(V) as in all higher group 15 elements. The energy of a bond to carbon in this group decreases in the order P > As > Sb > Bi. [3] The first reported use of bismuth in organic chemistry was in oxidation of alcohols by Frederick Challenger in 1934 (using Ph3Bi(OH)2). [4] Knowledge about methylated species of bismuth in environmental and biological media is limited. [5]
Triethylbismuth, the first known organobismuth compound, was prepared in 1850 by Löwig and Schweizer from iodoethane and a potassium–bismuth alloy. As with most trialkylbismuth compounds, BiEt3 has an extremely pungent and unpleasant odor, and is spontaneously oxidized in air. [6] The chemistry of these complexes first began receiving significant attention when Grignard reagents and organolithium compounds became available.
Triorganobismuth(III) compounds are monomeric with pyramidal structures reminiscent of organophosphorus(III) chemistry. The halides however adopt hypervalent structures. This trend is illustrated by the sheet-like structure adopted by methylbismuth dichloride. [7]
Most aliphatic organobismuth(III) compounds oxidize easily, with the lighter members pyrophoric. Dialkylhalobismuthines cannot be stored, as they decompose under even inert atmospheres. [8] : 413
Diarylbismuthines are among the most powerful sneezing agents known. [8] : 413
Organobismuth heterocycles are based on Bi(III). The cyclic compound bismole, a structural analog of pyrrole, has not been isolated, but substituted bismoles are known. [9] Bismabenzene has been detected in the laboratory. [10]
The most general and widely-used methodology for homoleptic trialkyl- and triarylbismuth complex synthesis reacts BiX3 with organolithium or -magnesium reagents: [6]
Triorganobismuth compounds were first prepared instead from K3Bi and organic halides: [6]
This method is generally more difficult and produces a lower yield. However, it remained as of 2006 the only method for e.g., (Me3Si)3Bi synthesis. [6]
Triaryl bismuth(III) compounds are typically air-stable crystalline solids, and the substituents will react before the carbon-bismuth bonds under appropriate conditions: [11]
Asymmetric organobismuth compounds proceed most naturally from the (unstable) organobismuth halides RBiX2 and R2BiX. [6]
In industry, triarylbismuth compounds catalyze various alkene and alkyne polymerizations. [8] : 415
Triarylbismuth compounds have very limited use in organic synthesis. [12] Their bonds are weak, and easily displaced by other elements, metallic or nonmetallic. [8] : 413 Such reactions proceed more readily than for the lighter congeners. Of course, triphenylbismuth undergoes redistribution with its trihalide to give the mixed derivatives such as diphenylbismuth chloride (Ph2BiCl). [13] Bbismuth(III) reagents can transfer substituents to thallium(III) compounds: [8] : 414
Bi(CH2=CMe)3 + 3 TlCl3 → (CH2=CMe)2TlCl + 2 BiCl3 at −40 °C
Triarylbismuth(III) compounds may also be employed in C–N and C–C bond-forming transformations with an appropriate metal co-catalyst. For instance, Barton and coworkers demonstrated that amines could be N-arylated with a bismuth(III) reagent in the presence of copper(II) salt. [14]
Likewise acylchlorides react under Pd(0) catalysis to form a variety of phenyl ketones. [15] Although not formally arenes, tricyclopropylbismuth(III) reagents react with aryl halides and triflates under Pd(0) catalysis in a similar fashion to afford a variety of aryl and heteroaryl cyclopropanes: [16]
The thermal stability of R5M compounds decrease in the order As > Sb > Bi. The aryl compounds are more stable than alkyl compounds. Me5Bi decomposes explosively at 20°C.[ citation needed ]
The nature of the aryl ligands is important in determining whether the complex's geometry is trigonal bipyramidal or square planar and its color. [6] In general, homoleptic compounds of the type Ar5Bi adopt square pyramidal structures. The pentaphenyl compound is deeply colored and thermochromic, possibly because of equilibration between geometries. [17]
Carboxylates rarely form chelating complexes of bismuth. Instead, organobismuth carboxylates are typically polymeric, with each oxygen on the carboxylate coordinating to a different bismuth atom. [18] : 330–332, 344–345 The same is not true for xanthates. [18] : 334, 340
Bismuth halides coordinated to arenes are piano-stool complexes. [18] : 337, 341–343
Interestingly, although very few inorganic BiV compounds are known, there is a wide variety of pentacoordinate organobismuth complexes. [8] : 415 Triarylorganobismuth complexes easily oxidize to bismuth(V) complexes when treated with chlorine or bromine, giving Ar3BiX2 (X = Cl, Br). Reactions with iodine instead displace ligands to give tricoordinate Ar3−xBiIx, whilst reactions with fluorine are too vigorous for control. [6]
All-carbon organobismuth(V) complexes may then be accessed from displacement of the newly formed bismuth-halogen bond with an alkyl or aryl lithium or Grignard reagent. For example:
Unstable, purple Ph5Bi was the first to be synthesized so. [6]
Bi(V) easily forms an onium ion for example by protonation with p-toluenesulfonic acid: [19]
Pentaphenylbismuth forms an ate complex upon treatment with phenyl lithium: [20]
Organobismuth(V) reagents are useful for a wide variety of organic transformations. Compared to their lighter congeners, Bi(V) compounds are strong oxidants, dehydrogenating alcohols of all kinds to the carbonyl and cleaving glycols to the aldehyde. They also engage in aryl transfers. [6]
The compounds Ph3Bi(OOtBu)2, Ph3BiCO3 and (Ph3BiCl)2O have been investigated for oxime, thiol, phenol, and phosphine oxidation. [21] [ page needed ] In general, oxidation accelerates when the aryl ligands have electron-withdrawing substituents, and attacks alcohols before thiols or selenides. [8] : 416–417 Hydrazines dehydrogenate to azo compounds and thiols to a mixture of sulfides and disulfides. [8] : 417–418 High yields require strongly basic conditions (absent it, the carbonate is the most effective), suggesting that the active species are triarylbismuth oxides. However, pentaarylbismuth compounds will also abstract hydrogen. [8] : 416–417
In general, bismuth(V) compounds arylate inefficiently, transferring only one of the five ligands to the substrate [22] and leaving behind a triarylbismuth(III) waste. [23] Reoxidizing the BiIII complex to BiV is hard, and impedes closing a catalytic cycle around this chemistry. [22] Nevertheless, Ph5Bi and Ph3BiCl2 do arylate 1,3-dicarbonyls and arenes: [24]
In the reaction, the bismuth(V) reagent loses an aryl group and binds to oxygen. The subsequent arylation and elimination are asynchronous and concerted: [23]
Adjacent electron-pair donors determine regioselectivity.
In the presence of a copper salt, such reagents arylate amines and alcohols. Under ultraviolet light as well, they monoarylate glycols. Steric hindrance governs their high selectivity: secondary alcohols are arylated over tertiary ones, and axial alcohols arylated over equatorial ones. [8] : 417–431
Iron(III) chloride describes the inorganic compounds with the formula FeCl3(H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated forms, which are both hygroscopic. They feature iron in its +3 oxidation state. The anhydrous derivative is a Lewis acid, while all forms are mild oxidizing agents. It is used as a water cleaner and as an etchant for metals.
Cerium(III) chloride (CeCl3), also known as cerous chloride or cerium trichloride, is a compound of cerium and chlorine. It is a white hygroscopic salt; it rapidly absorbs water on exposure to moist air to form a hydrate, which appears to be of variable composition, though the heptahydrate CeCl3·7H2O is known. It is highly soluble in water, and (when anhydrous) it is soluble in ethanol and acetone.
The Stille reaction is a chemical reaction widely used in organic synthesis. The reaction involves the coupling of two organic groups, one of which is carried as an organotin compound (also known as organostannanes). A variety of organic electrophiles provide the other coupling partner. The Stille reaction is one of many palladium-catalyzed coupling reactions.
The Suzuki reaction or Suzuki coupling is an organic reaction that uses a palladium complex catalyst to cross-couple a boronic acid to an organohalide. It was first published in 1979 by Akira Suzuki, and he shared the 2010 Nobel Prize in Chemistry with Richard F. Heck and Ei-ichi Negishi for their contribution to the discovery and development of noble metal catalysis in organic synthesis. This reaction is sometimes telescoped with the related Miyaura borylation; the combination is the Suzuki–Miyaura reaction. It is widely used to synthesize polyolefins, styrenes, and substituted biphenyls.
Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is highly soluble in water, giving pale green solutions.
Thionyl chloride is an inorganic compound with the chemical formula SOCl2. It is a moderately volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately 45,000 tonnes per year being produced during the early 1990s, but is occasionally also used as a solvent. It is toxic, reacts with water, and is also listed under the Chemical Weapons Convention as it may be used for the production of chemical weapons.
The Hiyama coupling is a palladium-catalyzed cross-coupling reaction of organosilanes with organic halides used in organic chemistry to form carbon–carbon bonds. This reaction was discovered in 1988 by Tamejiro Hiyama and Yasuo Hatanaka as a method to form carbon-carbon bonds synthetically with chemo- and regioselectivity. The Hiyama coupling has been applied to the synthesis of various natural products.
The Ullmann condensation or Ullmann-type reaction is the copper-promoted conversion of aryl halides to aryl ethers, aryl thioethers, aryl nitriles, and aryl amines. These reactions are examples of cross-coupling reactions.
Organozinc chemistry is the study of the physical properties, synthesis, and reactions of organozinc compounds, which are organometallic compounds that contain carbon (C) to zinc (Zn) chemical bonds.
Organocopper chemistry is the study of the physical properties, reactions, and synthesis of organocopper compounds, which are organometallic compounds containing a carbon to copper chemical bond. They are reagents in organic chemistry.
In organic chemistry, the Buchwald–Hartwig amination is a chemical reaction for the synthesis of carbon–nitrogen bonds via the palladium-catalyzed coupling reactions of amines with aryl halides. Although Pd-catalyzed C–N couplings were reported as early as 1983, Stephen L. Buchwald and John F. Hartwig have been credited, whose publications between 1994 and the late 2000s established the scope of the transformation. The reaction's synthetic utility stems primarily from the shortcomings of typical methods for the synthesis of aromatic C−N bonds, with most methods suffering from limited substrate scope and functional group tolerance. The development of the Buchwald–Hartwig reaction allowed for the facile synthesis of aryl amines, replacing to an extent harsher methods while significantly expanding the repertoire of possible C−N bond formations.
Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. They are reagents in organic chemistry and are involved in major industrial processes.
Organoarsenic chemistry is the chemistry of compounds containing a chemical bond between arsenic and carbon. A few organoarsenic compounds, also called "organoarsenicals," are produced industrially with uses as insecticides, herbicides, and fungicides. In general these applications are declining in step with growing concerns about their impact on the environment and human health. The parent compounds are arsane and arsenic acid. Despite their toxicity, organoarsenic biomolecules are well known.
Organoantimony chemistry is the chemistry of compounds containing a carbon to antimony (Sb) chemical bond. Relevant oxidation states are SbV and SbIII. The toxicity of antimony limits practical application in organic chemistry.
The Heck–Matsuda (HM) reaction is an organic reaction and a type of palladium catalysed arylation of olefins that uses arenediazonium salts as an alternative to aryl halides and triflates.
Organocerium chemistry is the science of organometallic compounds that contain one or more chemical bond between carbon and cerium. These compounds comprise a subset of the organolanthanides. Most organocerium compounds feature Ce(III) but some Ce(IV) derivatives are known.
The Chan–Lam coupling reaction – also known as the Chan–Evans–Lam coupling is a cross-coupling reaction between an aryl boronic acid and an alcohol or an amine to form the corresponding secondary aryl amines or aryl ethers, respectively. The Chan–Lam coupling is catalyzed by copper complexes. It can be conducted in air at room temperature. The more popular Buchwald–Hartwig coupling relies on the use of palladium.
Pentamethylcyclopentadienyl rhodium dichloride dimer is an organometallic compound with the formula [(C5(CH3)5RhCl2)]2, commonly abbreviated [Cp*RhCl2]2 This dark red air-stable diamagnetic solid is a reagent in organometallic chemistry.
Bismuthinidenes are a class of organobismuth compounds, analogous to carbenes. These compounds have the general form R-Bi, with two lone pairs of electrons on the central bismuth(I) atom. Due to the unusually low valency and oxidation state of +1, most bismuthinidenes are reactive and unstable, though in recent decades, both transition metals and polydentate chelating Lewis base ligands have been employed to stabilize the low-valent bismuth(I) center through steric protection and π donation either in solution or in crystal structures. Lewis base-stabilized bismuthinidenes adopt a singlet ground state with an inert lone pair of electrons in the 6s orbital. A second lone pair in a 6p orbital and a single empty 6p orbital make Lewis base-stabilized bismuthinidenes ambiphilic.
Triphenylbismuthine is an organobismuth compound with the formula Bi(C6H5)3. It is a white, air-stable solid that is soluble in organic solvents. It is prepared by treatment of bismuth trichloride with phenylmagnesium bromide.