Dicarbonyltris(triphenylphosphine)ruthenium(0) or Roper's complex is a
ruthenium metal carbonyl.
In it, two
carbon monoxide ligands and three
triphenylphosphine 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
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Acetylene
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\ce
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Propyne
\ce
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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, and
dioxygen. The compound has a
trigonal bipyramidal molecular geometry 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 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 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 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 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:
:
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 has been oxidized to
carbon dioxide 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.
]
Applications
The derivative Ru(CO)2H2(PPh3)2, obtained by exposing the complex to hydrogen, is a catalyst 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 alkenes and the ortho C-H position of a