Dichlorotris(triphenylphosphine)ruthenium(II)
Encyclopedia
Dichlorotrisruthenium(II) is a coordination complex of ruthenium
. This chocolate brown solid is a precursor to other complexes including those used as homogeneous catalysis
.
.
When conducted in the presence of larger excess of triphenylphosphine, the synthesis affords black RuCl2(PPh3)4.
The coordination sphere of RuCl2(PPh3)3 can be viewed as either five-coordinate or octahedral. One coordination site is occupied by one of the hydrogen atoms of a phenyl group. This Ru---H agostic interaction
is long (2.59 Å) and weak. The low symmetry of the compound is reflected by the differing lengths of the Ru-P bonds: 2.374, 2.412, and 2.230 Å. The Ru-Cl bond lengths are both 2.387 Å.
to produce the all trans isomer of dichloro(dicarbonyl)bis(triphenylphosphine)ruthenium(II).
This kinetic product isomerizes to the cis adduct during recrystallization
. trans-RuCl2(dppe)2 forms upon treating RuCl2(PPh3)3 with dppe.
of chlorocarbons to alkenes.
Dichlorotris(triphenylphosphine)ruthenium(II) serves as a precatalyst for the hydrogenation
of alkenes, nitro compounds, ketones, carboxylic acids, and imines. On the other hand, it catalyzes the oxidation of alkanes to tertiary alcohols, amides to t-butyldioxyamides, and tertiary amines to α-(t-butyldioxyamides) using tert-butyl hydroperoxide. Using other peroxides, oxygen, and acetone, the catalyst can oxidize alcohols to aldehydes or ketones. Using dichlorotris(triphenylphosphine)ruthenium(II) the N-alkylation of amines with alcohols is also possible (see "borrowing hydrogen
").
RuCl2(PPh3)3 efficiently catalyzes carbon-carbon bond formation from cross couplings of alcohols through C-H activation of sp3 carbons in the presence of a Lewis acid
.
RuCl2(PPh3)3 efficiently catalyzes the decomposition of formic acid
into carbon dioxide
and hydrogen
gas in the presence of an amine
. Since carbon dioxide
can be trapped and hydrogenated on an industrial scale, formic acid
represents a potential storage and transportation medium.
Ruthenium
Ruthenium is a chemical element with 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 most chemicals. The Russian scientist Karl Ernst Claus discovered the element...
. This chocolate brown solid is a precursor to other complexes including those used as homogeneous catalysis
Homogeneous catalysis
In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
.
Synthesis and basic properties
RuCl2(PPh3)3 is the product of the reaction of ruthenium trichloride trihydrate with a methanolic solution of triphenylphosphineTriphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - 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...
.
- 2 RuCl3(H2O)3 + 7 PPh3 → 2 RuCl2(PPh3)3 + 2 HCl + 5 H2O + 1 OPPh3
When conducted in the presence of larger excess of triphenylphosphine, the synthesis affords black RuCl2(PPh3)4.
The coordination sphere of RuCl2(PPh3)3 can be viewed as either five-coordinate or octahedral. One coordination site is occupied by one of the hydrogen atoms of a phenyl group. This Ru---H agostic interaction
Agostic interaction
Agostic interaction is a term in organometallic chemistry for the interaction of a coordinately-unsaturated transition metal with a C-H bond, when the two electrons involved in the C-H bond enter the empty d-orbital of a transition metal, resulting in a three-center two-electron bond. Many...
is long (2.59 Å) and weak. The low symmetry of the compound is reflected by the differing lengths of the Ru-P bonds: 2.374, 2.412, and 2.230 Å. The Ru-Cl bond lengths are both 2.387 Å.
Substitution reactions
The triphenylphosphine ligands are labile and are readily substituted by other ligands. Dichlorotris(triphenylphosphine)ruthenium(II) reacts with carbon monoxideCarbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
to produce the all trans isomer of dichloro(dicarbonyl)bis(triphenylphosphine)ruthenium(II).
- RuCl2(PPh3)3 + 2 CO → trans,trans,trans-RuCl2(CO)2(PPh3)2 + PPh3
This kinetic product isomerizes to the cis adduct during recrystallization
Recrystallization
Recrystallization may refer to:*Recrystallization *Recrystallization *Recrystallization...
. trans-RuCl2(dppe)2 forms upon treating RuCl2(PPh3)3 with dppe.
- RuCl2(PPh3)3 + 2 dppe → RuCl2(dppe)2 + 3 PPh3
Use in organic synthesis
RuCl2(PPh3)3 facilitates oxidations, reductions, cross-couplings, cyclizations, and isomerization. It is used in the Kharasch additionKharasch addition
The Kharasch addition is an organic reaction and a metal-catalysed free radical addition of CXCl3 compounds to alkenes. The reaction was invented by Morris S. Kharasch in the 1940s.The basic reaction scheme runs as follows:...
of chlorocarbons to alkenes.
Dichlorotris(triphenylphosphine)ruthenium(II) serves as a precatalyst for the hydrogenation
Hydrogenation
Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
of alkenes, nitro compounds, ketones, carboxylic acids, and imines. On the other hand, it catalyzes the oxidation of alkanes to tertiary alcohols, amides to t-butyldioxyamides, and tertiary amines to α-(t-butyldioxyamides) using tert-butyl hydroperoxide. Using other peroxides, oxygen, and acetone, the catalyst can oxidize alcohols to aldehydes or ketones. Using dichlorotris(triphenylphosphine)ruthenium(II) the N-alkylation of amines with alcohols is also possible (see "borrowing hydrogen
Borrowing hydrogen
Borrowing hydrogen catalysis is an important catalytic concept that is based on the intermediate oxidation of an alcohol substrate to the corresponding aldehyde by the catalyst ; the intermediate aldehyde then reacts with e.g. a secondary amine in a condensation reaction to produce e.g...
").
RuCl2(PPh3)3 efficiently catalyzes carbon-carbon bond formation from cross couplings of alcohols through C-H activation of sp3 carbons in the presence of a Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
.
RuCl2(PPh3)3 efficiently catalyzes the decomposition of formic acid
Formic acid
Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...
into carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas in the presence of an amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
. Since carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
can be trapped and hydrogenated on an industrial scale, formic acid
Formic acid
Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...
represents a potential storage and transportation medium.