Metallaborane

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Structure of
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(C5(CH3)5)FeHCo(CO)3B4H7. Color code: yellow = B, blue = Fe & Co, red = O, gray = C. Cp*FeHCo(CO)3B4H7 XOJLAJ.jpg
Structure of (C5(CH3)5)FeHCo(CO)3B4H7. Color code: yellow = B, blue = Fe & Co, red = O, gray = C.

In chemistry, a metallaborane is a compound that contains one or more metal atoms and one or more boron hydride. These compounds are related conceptually and often synthetically to the boron-hydride clusters by replacement of BHn units with metal-containing fragments. Often these metal fragments are derived from metal carbonyls or cyclopentadienyl complexes. Their structures can often be rationalized by polyhedral skeletal electron pair theory. The inventory of these compounds is large, and their structures can be quite complex. [2] [3]

Contents

Examples

Chemical structure of
B4H8Fe(CO)3. As is customary for boron hydrides, the lines drawn between B and H do not represent 2-center, 2-electron bonds. B4H8Fe(CO)3.svg
Chemical structure of B4H8Fe(CO)3. As is customary for boron hydrides, the lines drawn between B and H do not represent 2-center, 2-electron bonds.

Two simple examples are B4H8Fe(CO)3 and B4H8Co(C5H5). The MB4 cores (M = Fe or Co) of these two compounds adopt structures expected for nido 5-vertex clusters. The iron compound is produced by reaction of diiron nonacarbonyl with pentaborane. B4H8Fe(CO)3 and cyclobutadieneiron tricarbonyl have similar structures.

Metallacarboranes

Structure of (Me4N )2[Fe(C2B9H11)2] , showing only one Me4N . KIWJOP.png
Structure of (Me4N )2[Fe(C2B9H11)2] , showing only one Me4N .

Even greater in scope than metalloboranes are metallacarboranes. These cages have carbon vertices, often CH, in addition to BH and M vertices. [2] A well-developed class of metallacarboranes are prepared from dicarbollides, anions of the formula [C2B9H11]2-. These anions function as ligands for a variety of metals, often forming sandwich complexes. [5]

Some metalloboranes are derived by the metalation of neutral carboranes. Illustrative are the six-and seven-vertex cages prepared from closo-C2B3H5. Reaction of this carborane with iron carbonyl sources gives closo Fe- and Fe2-containing products, according to these idealized equations: [6]

C2B3H5 + Fe2(CO)9 → C2B3H5Fe(CO)3 + Fe(CO)5 + CO
C2B3H5Fe(CO)3 + Fe2(CO)9 → C2B3H5(Fe(CO)3)2 + Fe(CO)5 + CO

A further example of insertion into a closo carborane is the synthesis of the yellow-orange solid closo-1,2,3-(CO)3FeC2B4H6:

closo−C2B4H8 + Fe2(CO)9 → closo−(CO)3FeC2B4H6 + Fe(CO)5 + CO

A closely related reaction involves the capping of an anionic nido carborane C2B4H7

closo−C2B4H8 + NaH → Na(nido−B4H7) + H2
Na(nido−B4H7 + CoCl2 + NaC5H5 → closo−(C5H5(CoB4H6 + 2 NaCl + ...

The last reaction is worked up with acid and air.

Related Research Articles

<span class="mw-page-title-main">Inorganic chemistry</span> Field of chemistry

Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.

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

A metallocene is a compound typically consisting of two cyclopentadienyl anions (C
5
H
5
, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to [Cp2ZrCH3]+ catalyze olefin polymerization.

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

Boranes is the name given to compounds with the formula BxHy and related anions. Many such boranes are known. Most common are those with 1 to 12 boron atoms. Although they have few practical applications, the boranes exhibit structures and bonding that differs strongly from the patterns seen in hydrocarbons. Hybrids of boranes and hydrocarbons, the carboranes are also well developed.

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

Decaborane, also called decaborane(14), is the borane with the chemical formula B10H14. This white crystalline compound is one of the principal boron hydride clusters, both as a reference structure and as a precursor to other boron hydrides. It is toxic and volatile, giving off a foul odor, like that of burnt rubber or chocolate.

<span class="mw-page-title-main">Cyclopentadienyl complex</span> Coordination complex of a metal and Cp⁻ ions

A cyclopentadienyl complex is a coordination complex of a metal and cyclopentadienyl groups. Cyclopentadienyl ligands almost invariably bind to metals as a pentahapto (η5-) bonding mode. The metal–cyclopentadienyl interaction is typically drawn as a single line from the metal center to the center of the Cp ring.

<span class="mw-page-title-main">Carborane</span> Class of chemical compounds

Carboranes are electron-delocalized clusters composed of boron, carbon and hydrogen atoms. Like many of the related boron hydrides, these clusters are polyhedra or fragments of polyhedra. Carboranes are one class of heteroboranes.

<span class="mw-page-title-main">Metal carbonyl</span> 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.

In chemistry the polyhedral skeletal electron pair theory (PSEPT) provides electron counting rules useful for predicting the structures of clusters such as borane and carborane clusters. The electron counting rules were originally formulated by Kenneth Wade, and were further developed by others including Michael Mingos; they are sometimes known as Wade's rules or the Wade–Mingos rules. The rules are based on a molecular orbital treatment of the bonding. These rules have been extended and unified in the form of the Jemmis mno rules.

<span class="mw-page-title-main">Dicobalt octacarbonyl</span> Chemical compound

Dicobalt octacarbonyl is an organocobalt compound with composition Co2(CO)8. This metal carbonyl is used as a reagent and catalyst in organometallic chemistry and organic synthesis, and is central to much known organocobalt chemistry. It is the parent member of a family of hydroformylation catalysts. Each molecule consists of two cobalt atoms bound to eight carbon monoxide ligands, although multiple structural isomers are known. Some of the carbonyl ligands are labile.

<span class="mw-page-title-main">Sandwich compound</span> Chemical compound made of two ring ligands bound to a metal

In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula CnHn, substituted derivatives and heterocyclic derivatives. Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the metallocenes.

<span class="mw-page-title-main">Caesium dodecaborate</span> Chemical compound

Caesium dodecaborate is an inorganic compound with the formula Cs2B12H12. It is a salt composed of caesium and dodecaborate(12) ions. The [B12H12]2− anion has been of great theoretical interest to the chemistry community.

In organometallic chemistry, a migratory insertion is a type of reaction 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.:

Transition metal hydrides are chemical compounds containing a transition metal bonded to hydrogen. Most transition metals form hydride complexes and some are significant in various catalytic and synthetic reactions. The term "hydride" is used loosely: some of them are acidic (e.g., H2Fe(CO)4), whereas some others are hydridic, having H-like character (e.g., ZnH2).

Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. Organoiron compounds are relevant in organic synthesis as reagents such as iron pentacarbonyl, diiron nonacarbonyl and disodium tetracarbonylferrate. While iron adopts oxidation states from Fe(−II) through to Fe(VII), Fe(IV) is the highest established oxidation state for organoiron species. Although iron is generally less active in many catalytic applications, it is less expensive and "greener" than other metals. Organoiron compounds feature a wide range of ligands that support the Fe-C bond; as with other organometals, these supporting ligands prominently include phosphines, carbon monoxide, and cyclopentadienyl, but hard ligands such as amines are employed as well.

<span class="mw-page-title-main">Cobalt tetracarbonyl hydride</span> Chemical compound

Cobalt tetracarbonyl hydride is an organometallic compound with the formula HCo(CO)4. It is a volatile, yellow liquid that forms a colorless vapor and has an intolerable odor. The compound readily decomposes upon melt and in absentia of high CO partial pressures forms Co2(CO)8. Despite operational challenges associated with its handling, the compound has received considerable attention for its ability to function as a catalyst in hydroformylation. In this respect, HCo(CO)4 and related derivatives have received significant academic interest for their ability to mediate a variety of carbonylation (introduction of CO into inorganic compounds) reactions.

<span class="mw-page-title-main">Iron tetracarbonyl dihydride</span> Chemical compound

Iron tetracarbonyl dihydride is the organometallic compound with the formula H2Fe(CO)4. This compound was the first transition metal hydride discovered. The complex is stable at low temperatures but decomposes rapidly at temperatures above –20 °C.

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

In organometallic chemistry, a dicarbollide is an anion of the formula [C2B9H11]2-. Various isomers exist, but most common is 1,2-dicarbollide derived from ortho-carborane. These dianions function as ligands, related to the cyclopentadienyl anion. Substituted dicarbollides are also known such as [C2B9H10(pyridine)] (pyridine bonded to B) and [C2R2B9H9]2- (R groups bonded to carbon).

In chemistry, the Jemmis mno rules represent a unified rule for predicting and systematizing structures of compounds, usually clusters. The rules involve electron counting. They were formulated by Eluvathingal Devassy Jemmis to explain the structures of condensed polyhedral boranes such as B20H16, which are obtained by condensing polyhedral boranes by sharing a triangular face, an edge, a single vertex, or four vertices. These rules are additions and extensions to Wade's rules and polyhedral skeletal electron pair theory. The Jemmis mno rule provides the relationship between polyhedral boranes, condensed polyhedral boranes, and β-rhombohedral boron. This is similar to the relationship between benzene, condensed benzenoid aromatics, and graphite, shown by Hückel's 4n + 2 rule, as well as the relationship between tetracoordinate tetrahedral carbon compounds and diamond. The Jemmis mno rules reduce to Hückel's rule when restricted to two dimensions and reduce to Wade's rules when restricted to one polyhedron.

<span class="mw-page-title-main">Ortho-carborane</span> Chemical compound

Ortho-carborane is the organoboron compound with the formula C2B10H12. The prefix ortho is derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant polymers to medical applications. It is a colorless solid that melts, without decomposition, at 320 °C.

Dicarbollylcobaltate(III) anion is a dicarbollide cluster compound containing cobaltic cation (III) as a metal center. The dicarbollylcobaltate(III) anion can be abbreviated to [COSAN]- or [CoD]-. The center cobaltic cation is sandwiched by two dicarbollide clusters, so that it can be regarded as the carboranyl version of Cp2Co+.

References

  1. Peldo, Melanie A.; Beatty, Alicia M.; Fehlner, Thomas P. (2002). "Routes to Compounds Containing M−B Bonds. Reaction of [Cp*FeH2]2 with BH3·THF, Yielding the Hydrogen-Rich arachno-Ferrapentaborane 1-Cp*FeB4H11 (Cp* = η5-C5Me5)". Organometallics. 21 (14): 2821–2823. doi:10.1021/om020273y.
  2. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  3. Grimes, Russell N. (1982). Metal Interactions with Boron Clusters. ISBN   9780306409332.
  4. Kang, H. C.; Lee, S. S.; Knobler, C. B.; Hawthorne, M. F. (1991). "Syntheses of Charge-Compensated Dicarbollide Ligand Precursors and Their Use in the Preparation of Novel Metallacarboranes". Inorganic Chemistry. 30 (9): 2024–2031. doi:10.1021/ic00009a015.
  5. Sivaev, I. B.; Bregadze, V. I. (2000). "Chemistry of Nickel and Iron Bis(dicarbollides). A Review". Journal of Organometallic Chemistry. 614–615: 27–36. doi:10.1016/S0022-328X(00)00610-0.
  6. Grimes, R. N. (1982). "Metallacarboranes and Metallaboranes". Comprehensive Organometallic Chemistry. pp. 459–542. doi:10.1016/B978-008046518-0.00009-X. ISBN   9780080465180.