Dicarbonyltris(triphenylphosphine)ruthenium(0) or Roper's complex is a
ruthenium
Ruthenium is a chemical element with the Symbol (chemistry), symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to ...
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 ch ...
.
In it, two
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 ...
ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
s and three
triphenylphosphine
Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists a ...
ligands are coordinated to a central ruthenium(0) center.
In solution, this compound readily dissociates one of the three phosphine ligands, thereby generating a reactive 16-electron complex that binds or oxidatively adds a variety of substrates such as
alkyne
\ce
\ce
Acetylene
\ce
\ce
\ce
Propyne
\ce
\ce
\ce
\ce
1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s,
olefin
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
s,
dihydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and ...
, and
dioxygen
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are:
*A ...
. The compound has a
trigonal bipyramidal molecular geometry
In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not identi ...
and, in solution, exists as a mixture of two isomers that rapidly interconvert. The complex is air stable as a solid, but its solutions oxygenate in air to afford Ru(CO)
2(PPh
3)
2(η
2-O
2).
Preparation
The compound can be prepared by
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
reduction of the corresponding ruthenium(II) dichloride complex in the presence of an excess of phosphine. The 16-electron intermediate can actually be isolated.
:Ru(CO)
2Cl
2(PPh
3)
2 + Mg + PPh
3 → Ru(CO)
2(PPh
3)
3 + MgCl
2
An improved
base-promoted method involves the reduction of a ruthenium(II) carbonyl chloride with base in the presence of excess phosphine.
The overall reaction for this
one-pot synthesis
In chemistry a one-pot synthesis is a strategy to improve the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one reactor. This is much desired by chemists because avoiding a lengthy separ ...
is:
:Ru(CO)
3Cl
2(thf) + 3 PPh
3 + 4
Et4H → Ru(CO)
2(PPh
3)
2 +
Et4sub>2
O3+ 2
Et4l + 2H
2O + thf
The first step in this sequence is the formation of a metallocarboxylate by nucleophilic attack of
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
anion on a CO ligand to form a
formate
Formate (IUPAC name: methanoate) is the conjugate base of formic acid. Formate is an anion () or its derivatives such as ester of formic acid. The salts and esters are generally colorless.Werner Reutemann and Heinz Kieczka "Formic Acid" in ''Ull ...
anion:
:Ru(CO)
3Cl
2(thf) +
Et4H →
Et4Ru(CO)
2(COOH)Cl
2(thf)]
Next solvated
tetrahydrofuran
Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...
is replaced by phosphine:
:
Et4Ru(CO)
2(COOH)Cl
2(thf)] + PPh
3 →
Et4Ru(CO)
2(COOH)Cl
2(PPh
3)] + thf
Next the formate ligand is
deprotonation, deprotonated again by
hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
:
:
Et4Ru(CO)
2(COOH)Cl
2(PPh
3)] +
Et4H →
Et4sub>2
u(CO)2(COO)Cl2(PPh3) + H
2O
These three reactions mean that
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 ...
has been oxidized to
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
with the concomitant reduction of Ru(II) to Ru(0). Finally, the two remaining chloride ligands are replaced by two more phosphine groups and the carbon dioxide leaves:
:
Et4sub>2
u(CO)(COO)Cl2(PPh3)+ 2 PPh
3 → Ru(CO)
2(PPh
3)
3 + CO
2 + 2
Et4l
The generated carbon dioxide is trapped as
Et4sub>2
O3
History
The complex was first reported by Warren R Roper and his coworkers in 1972 in an era where oxidative addition reactions to ''d''
8 metal complexes were first being systematically examined.
[ Being zero-valent and carrying only two CO ligands, the complex is highly nucleophilic. Many of its reactions parallel those for ]Vaska's complex
Vaska's complex is the trivial name for the chemical compound ''trans''-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO) (C6H5)3sub>2. This square planar diamagnetic organometallic complex consists of a central iridi ...
.
Applications
The derivative Ru(CO)2H2(PPh3)2, obtained by exposing the complex to hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
, is a catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
in the Murai olefin coupling
Murai may refer to:
*Murai (surname), Japanese surname
*Murai, Singapore, area in Western Water Catchment
*Murai Reservoir
The Western Water Catchment is a planning area located in the West Region of Singapore. The planning area borders Tuas an ...
reaction between terminal alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
s and the ortho C-H position of a