Metal sulfur dioxide complex

Last updated

In organometallic chemistry, metal sulfur dioxide complexes are complexes that contain sulfur dioxide, SO2, bonded to a transition metal. [1] Such compounds are common but are mainly of theoretical interest. Historically, the study of these compounds has provided insights into the mechanisms of migratory insertion reactions.

Contents

Bonding modes

Portion of the structure of [Ni(SO2)6](AsF6)2, showing the dication and one of two AsF6 anions. EntryWithCollCode80473.png
Portion of the structure of [Ni(SO2)6](AsF6)2, showing the dication and one of two AsF6 anions.

.

Sulfur dioxide forms complexes with many transition metals. Most numerous are complexes with metals i in oxidation state 0 or +1. [1]

In most cases SO2 binds in monodentate fashion, attaching to the metal through sulfur. Such complexes are further subdivided according to the planarity or pyramidalization at sulfur. The various bonding modes are:

More exotic bonding modes are known for clusters.

Illustrative SO2 complexes of soft metal centers. From the left, Fe(CO)2[P(OPh)3]2(e -SO2), IrCl(CO)(PPh3)2(e -SO2), Mo(CO)2(PMe3)3(e -SO2), and the A-frame complex Rh2(bis(diphenylphosphino)methane)2Cl(CO)2(m-SO2). SO2CmpxesUpgrade.png
Illustrative SO2 complexes of soft metal centers. From the left, Fe(CO)2[ P(OPh)3 ]2(η -SO2), IrCl(CO)(PPh3)2(η -SO2), Mo(CO)2(PMe3)3(η -SO2), and the A-frame complex Rh2(bis(diphenylphosphino)methane)2Cl(CO)2(μ-SO2).

Preparation

Complexes of the transition metals are usually generated simply by treating the appropriate metal complex with SO2. The adducts are often weak. In some cases, SO2 displaces other ligands. [3]

A large number of labile O-bonded SO2 complexes arise from the oxidation of a suspension of the metals in liquid SO2, an excellent solvent. [2]

Reactions

The main reaction of sulfur dioxide promoted by transition metals is its reduction by hydrogen sulfide. Known as the Claus process, this reaction is conducted on a large scale as a way to remove hydrogen sulfide that arises in hydrotreating processes in refineries.

Insertion of SO2 into metal-ligand bonds

Of academic interest, SO2 acts like a Lewis acid towards the alkyl ligand. [4] The pathway for the insertion of SO2 into metal alkyl bond begins with attack of the alkyl nucleophile on the sulfur centre in SO2. The "insertion" proceed the sulfur dioxide between the metal and the alkyl ligand leads to the O, O'-sulphinate. Alternatively an O-sulphinate can arise. Both of these intermediates commonly convert to an S-sulphinate. [5] S-sulphinate has sulfur–oxygen stretching frequencies from 1250–1000 cm−1 and 1100–1000 cm−1. The O, O'-sulphinate and O-sulphinate are difficult to distinguish as they have stretching frequencies from 1085–1050 cm−1 and 1000–820 cm−1 or lower. The pathway involving the O, O' sulphinate can generally be ruled out if the original metal complex fulfilled the 18-electron rule because the two metal–oxygen bonds would exceed the 18 electron rule. [6] The pathway by which SO2 inserts into a square planar alkyl complexes involves the formation of an adduct. Thereafter, the alkyl ligand migrates to the SO2. [7]

Pathway for insertion of SO2 into Au-methyl bonds of a square planar Au(III)) complex. AuMe+SO2Insn.png
Pathway for insertion of SO2 into Au-methyl bonds of a square planar Au(III)) complex.

S2O complexes

Several complexes of disulfur monoxide are known. Most are formed by oxidation peroxide oxidation of a disulfur ligand. In these complexes, the S2O ligand is invariably bound in an η2-S,S manner. Selected examples: [Ir(dppe)2S2O]+, OsCl(NO)(PPh3)2S2O, NbCl(η-C5H5)2S2O, Mn(CO)2(η-C5Me5)S2O, Re(CO)2(η-C5Me5)S2O, Re(CO)2(η-C5H5)S2O. [8]

Mo2(S2O)2(S2CNEt2)4 arises when the dithiocarbamate complex Mo(CO)2(S2CNEt2)2 is oxidized with elemental sulfur in air. Another way to form these complexes is to combine OSNSO2·R complexes with hydrogen sulfide. Complexes formed in this way are: IrCl(CO)(PPh3)2S2O; Mn(CO)2(η-C5H5)S2O. With hydrosulfide and a base followed by oxygen, OsCl(NO)(PPh3)2S2O can be made.

Related Research Articles

Organometallic chemistry Study of organic compounds containing metal(s)

Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide, cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.

Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidative addition is often a step in catalytic cycles, in conjunction with its reverse reaction, reductive elimination.

Vaskas complex Chemical compound

Vaska's complex is the trivial name for the chemical compound trans-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO)[P(C6H5)3]2. This square planar diamagnetic organometallic complex consists of a central iridium atom bound to two mutually trans triphenylphosphine ligands, carbon monoxide and a chloride ion. The complex was first reported by J. W. DiLuzio and Lauri Vaska in 1961. Vaska's complex can undergo oxidative addition and is notable for its ability to bind to O2 reversibly. It is a bright yellow crystalline solid.

Triphenylphosphine Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

Metal carbonyl Coordination complexes of transition metals with carbon monoxide ligands

Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes.

Hapticity Number of contiguous atoms in a ligand that bond to the central atom in a coordination complex

In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.

<span class="mw-page-title-main">Metal nitrosyl complex</span> Complex of a transition metal bonded to nitric oxide: Me–NO

Metal nitrosyl complexes are complexes that contain nitric oxide, NO, bonded to a transition metal. Many kinds of nitrosyl complexes are known, which vary both in structure and coligand.

<span class="mw-page-title-main">Organoactinide chemistry</span> Study of chemical compounds containing actinide-carbon bonds

Organoactinide chemistry is the science exploring the properties, structure and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.

<span class="mw-page-title-main">Organotitanium compound</span>

Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis and reactions. They are reagents in organic chemistry and are involved in major industrial processes.

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.

A migratory insertion is a type of reaction in organometallic chemistry wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.:

<span class="mw-page-title-main">Organoiridium compound</span>

Organoiridium chemistry is the chemistry of organometallic compounds containing an iridium-carbon chemical bond. Organoiridium compounds are relevant to many important processes including olefin hydrogenation and the industrial synthesis of acetic acid. They are also of great academic interest because of the diversity of the reactions and their relevance to the synthesis of fine chemicals.

Dioxygen complexes are coordination compounds that contain O2 as a ligand. The study of these compounds is inspired by oxygen-carrying proteins such as myoglobin, hemoglobin, hemerythrin, and hemocyanin. Several transition metals form complexes with O2, and many of these complexes form reversibly. The binding of O2 is the first step in many important phenomena, such as cellular respiration, corrosion, and industrial chemistry. The first synthetic oxygen complex was demonstrated in 1938 with cobalt(II) complex reversibly bound O2.

Organoplatinum chemistry is the chemistry of organometallic compounds containing a carbon to platinum chemical bond, and the study of platinum as a catalyst in organic reactions. Organoplatinum compounds exist in oxidation state 0 to IV, with oxidation state II most abundant. The general order in bond strength is Pt-C (sp) > Pt-O > Pt-N > Pt-C (sp3). Organoplatinum and organopalladium chemistry are similar, but organoplatinum compounds are more stable and therefore less useful as catalysts.

<span class="mw-page-title-main">Organorhodium chemistry</span>

Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium-carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions.

Metal-phosphine complex

A metal-phosphine complex is a In coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0).

Half sandwich compound Class of coordination compounds

Half sandwich compounds, also known as piano stool complexes, are organometallic complexes that feature a cyclic polyhapto ligand bound to an MLn center, where L is a unidentate ligand. Thousands of such complexes are known. Well-known examples include cyclobutadieneiron tricarbonyl and (C5H5)TiCl3. Commercially useful examples include (C5H5)Co(CO)2, which is used in the synthesis of substituted pyridines, and methylcyclopentadienyl manganese tricarbonyl, an antiknock agent in petrol.

In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. Such compounds are intermediates in many catalytic reactions that convert alkenes to other organic products.

Transition metal acyl complexes

Transition metal acyl complexes describes organometallic complexes containing one or more acyl (RCO) ligands. Such compounds occur as transient intermediates in many industrially useful reactions, especially carbonylations.

In chemistry, transition metal silyl complexes describe coordination complexes in which a transition metal is bonded to an anionic silyl ligand, forming a metal-silicon sigma bond. This class of complexes are numerous and some are technologically significant as intermediates in hydrosilylation. These complexes are a subset of organosilicon compounds.

References

  1. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. 1 2 3 Mews, R.; Lork, E.; Watson, P. G.; Görtler, B. (2000). "Coordination Chemistry in and of Sulfur Dioxide". Coord. Chem. Rev. 197 (1): 277–320. doi:10.1016/S0010-8545(99)00191-5.
  3. ↑ Schenk, W. A. (1987). "Sulfur Oxides as Ligands in Coordination Compounds". Angew. Chem. Int. Ed. 26 (2): 98–109. doi:10.1002/anie.198700981.
  4. ↑ Douglas, B. E.; McDaniel, D. H.; Alexander, J. J. (1994). Concepts and Models of Inorganic Chemistry (3rd ed.). New York: John Wiley & Sons, Inc. ISBN   978-0-471-62978-8.
  5. ↑ Wojcicki, A. (1974). "Insertion Reactions of Transition Metal–Carbon σ-Bonded Compounds II. Sulfur Dioxide and Other Molecules". In Stone, F. G. A.; West, R. (eds.). Advances in Organometallic Chemistry . Vol. 12. pp. 31–81. doi:10.1016/S0065-3055(08)60450-5. ISBN   9780120311125.
  6. ↑ Alexander, J. J. (1985). Hartley, F. R.; Patai, S. (eds.). The Chemistry of the Metal-Carbon Bond, Vol. 2: The Nature and Cleavage of Metal-Carbon Bonds. New York: John Wiley & Sons.
  7. ↑ Puddephatt, R. J.; Stalteri, M. A. (1980). "Competition between Insertion of Sulfur Dioxide into the Methyl– or Phenyl–Transition Metal Bond". J. Organomet. Chem. 193 (1): C27–C29. doi:10.1016/S0022-328X(00)86091-X.
  8. ↑ Hill, Anthony F. (1994). Organotransition Metallic Chemistry of Sulfur Dioxide Analogs. Advances in Organometallic Chemistry. Vol. 36. pp. 159–227. doi:10.1016/S0065-3055(08)60391-3. ISBN   9780120311361.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.