Dirhenium decacarbonyl is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the chemical formula Re₂(CO)₁₀ . Commercially available, it is used as a starting point for the synthesis of many rhenium

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

complexes. It was first reported in 1941 by

Walter Hieber Walter Hieber (18 December 1895 – 29 November 1976) was an inorganic chemist, known as the father of metal carbonyl chemistry. He was born 18 December 1895 and died 29 November 1976. Hieber's father was Johannes Hieber, an influential evangel ...

, who prepared it by reductive carbonylation of rhenium. The compound consists of a pair of

square pyramidal In molecular geometry, square pyramidal geometry describes the shape of certain Chemical compound, compounds with the formula where L is a ligand. If the ligand atoms were connected, the resulting shape would be that of a Square pyramid, pyram ...

Re(CO)₅ units joined via a Re-Re bond, which produces a homoleptic carbonyl complex.

History

In the 1930s

Robert Mond Sir Robert Ludwig Mond, Royal Society, FRS, FRSE (9 September 1867 – 22 October 1938) was a British people, British chemist and archaeologist. Early life and education Mond was born at Farnworth, Widnes, Lancashire, the elder son of Ludwig Mo ...

developed methods which used increased pressure and temperature to produce various forms of

metal carbonyl 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 c ...

. A prominent scientist of the twentieth century,

was crucial to the further development of specifically the dirhenium decacarbonyl. Initial efforts produced mononuclear metal complexes, but upon further evaluation, Hieber discovered that by using Re₂O₇ as a starting material with no solvent, a dirhenium complex could be achieved producing a Re-Re interaction.

Structure and properties

The crystal structure of Re₂(CO)₁₀ is relatively well known. The compound consists of a pair of

Re(CO)₅ units linked by a Re-Re bond. There are two different conformations that can occur: staggered and eclipsed. The

eclipsed conformation In chemistry an eclipsed conformation is a conformation in which two substituents X and Y on adjacent atoms A, B are in closest proximity, implying that the torsion angle X–A–B–Y is 0°. Such a conformation can exist in any open chain ...

occurs about 30% of the time, producing a D_4h point group, but the staggered form, with point group D_4d, is more stable. The Re-Re bond length was experimentally found to be 3.04Å. The Re atom exists in a slightly distorted octahedral configuration with the C axial-Re-C equatorial angle equal to 88°. The mean Re-C bond length of 2.01 Å is the same for the axial and

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

positions. The mean C-O distance is 1.16 Å. This compound has a broad IR absorption band at 1800 cm⁻¹ region can be assigned to two components centered at 1780 and 1830 cm⁻¹, resulting from CO adsorption. The remaining nine CO groups in Re₂(CO)₁₀ give the complex IR absorption in the 1950–2150 cm⁻¹ region. Free Re₂(CO)₁₀ (

point symmetry In geometry, a point reflection (point inversion, central inversion, or inversion through a point) is a type of isometry of Euclidean space. An object that is invariant under a point reflection is said to possess point symmetry; if it is invari ...

D_4d ) has a CO stretch representation of 2A₁+E₂ + E₃+ 2B₂ +E₁, where 2B₂ + E₁ are IR active. For an axially perturbed (C_4v) Re₂(CO)₁₀ molecule, the CO stretch representation was found to be 2E+B₁+B₂+3A₁, where the IR active modes are 2E+3A₁. Its identity can also be confirmed by mass spectrometry, using the isotopic pattern of rhenium (¹⁸⁵Re and ¹⁸⁷Re).

Synthesis

Dirhenium decacarbonyl may be obtained by reductive carbonylation of

rhenium(VII) oxide Rhenium(VII) oxide is the inorganic compound with the formula Re2 O7. This yellowish solid is the anhydride of HOReO3. Perrhenic acid, Re2O7·2H2O, is closely related to Re2O7. Re2O7 is the raw material for all rhenium compounds, being the volat ...

(Re₂O₇) at 350 atm and 250 °C. :Re₂O₇ + 17 CO → Re₂(CO)₁₀ + 7 CO₂ It can also be prepared by the reaction of a methanol solution of

sodium perrhenate Sodium perrhenate (also known as sodium rhenate(VII)) is the inorganic compound with the formula NaReO4. It is a white salt that is soluble in water. It is a common precursor to other rhenium compounds. Its structure resembles that of sodium per ...

and

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

at 230 °C and 115 atm.

Reactions

The carbonyl ligands may be displaced by other ligands such as

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

s and

phosphite The general structure of a phosphite ester showing the lone pairs on the P In organic chemistry, a phosphite ester or organophosphite usually refers to an organophosphorous compound with the formula P(OR)3. They can be considered as esters of a ...

s (denoted L). ::Re₂(CO)₁₀ + 2 L → Re₂(CO)₈L₂ This compound may also be "cracked" to mononuclear Re(I) carbonyl complexes by halogenation: :Re₂(CO)₁₀ + X₂ → 2 Re(CO)₅X (X = Cl, Br, I) When bromine is used, bromopentacarbonylrhenium(I) is formed, which is an intermediate for many more rhenium complexes. This compound may also be hydrogenated to form various polyrhenium complexes, eventually giving elemental rhenium. :Re₂(CO)₁₀ → H₃Re₃(CO)₁₂ → H₅Re₄(CO)₁₂ → Re (metal) In the presence of water,

photolysis Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by photons. It is defined as the interaction of one or more photons with one target molecule. ...

of Re₂(CO)₁₀ yields a hydroxide complex: :Re₂(CO)₁₀ → HRe(CO)₅ + Re₄(CO)₁₂(OH)₄ This reaction includes the cleavage of Re-Re bond and the synthesis of HRe(CO)₅, which can be used to prepare surface structures designed to incorporate isolated surface-bound Re carbonyl complexes. Loss of a carbonyl ligand by photolysis generates a

coordinatively unsaturated In chemistry, a saturated compound is a chemical compound (or ion) that resists the addition reactions, such as hydrogenation, oxidative addition, and binding of a Lewis base. The term is used in many contexts and for many classes of chemical ...

complex that undergoes

oxidative addition 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. Oxidat ...

of Si-H bonds, for example: :Re₂(CO)₁₀ + HSiCl₃* → (CO)₅ReHRe(CO)₄SiCl₃ + CO

Applications

Rhenium-based catalysis have been used in metathesis, reforming,

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...

and various hydrotreating processes such as hydrodesulfurization. Re₂(CO)₁₀ can be used to promote the silation of alcohols and prepare the silyl ethers, and its reaction: :RSiH₃ + R'OH → RH₂SiOR' + H₂.

References