Ruthenium(III) chloride is the
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the formula RuCl
3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl
3·''x''H
2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of
water of crystallization
In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is ...
, often approximating to a trihydrate, is a commonly used starting material in
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 ...
chemistry.
Preparation and properties
Anhydrous ruthenium(III) chloride is usually prepared by heating powdered ruthenium metal with
chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
. In the original synthesis, the chlorination was conducted in the presence of
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 ...
, the product being carried by the gas stream and crystallising upon cooling. Two allotropes of RuCl
3 are known. The black α-form adopts the
CrCl3-type structure with long Ru-Ru contacts of 346
pm. This allotrope has honeycomb layers of Ru
3+ which are surrounded with an octahedral cage of Cl
− anions. The ruthenium cations are magnetic residing in a low-spin J~1/2 ground state with net angular momentum L=1. Layers of α-RuCl
3 are stacked on top of each other with weak
Van-der-Waals forces. These can be cleaved to form mono-layers using scotch tape.
The dark brown
metastable
In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy.
A ball resting in a hollow on a slope is a simple example of me ...
β-form crystallizes in a hexagonal cell; this form consists of infinite chains of face-sharing octahedra with Ru-Ru contacts of 283 pm, similar to the structure of
zirconium trichloride
Zirconium(III) chloride is an inorganic compound with formula ZrCl3. It is a blue-black solid that is highly sensitive to air.
Preparation
The material was first claimed by Ruff and Wallstein who reduced zirconium tetrachloride with aluminium t ...
. The β-form is irreversibly converted to the α-form at 450–600 °C. The β-form is diamagnetic, whereas α-RuCl
3 is paramagnetic at room temperature.
RuCl
3 vapour decomposes into the
elements at high temperatures ; the
enthalpy change
Enthalpy , a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant p ...
at 750 °C (1020 K), Δ
diss''H''
1020 has been estimated as +240 kJ/mol.
Solid state physics
α-RuCl
3 was proposed as a candidate for a
Kitaev quantum spin liquid
In condensed matter physics, a quantum spin liquid is a phase of matter that can be formed by interacting quantum spins in certain magnetic materials. Quantum spin liquids (QSL) are generally characterized by their long-range quantum entangleme ...
state when
neutron scattering
Neutron scattering, the irregular dispersal of free neutrons by matter, can refer to either the naturally occurring physical process itself or to the man-made experimental techniques that use the natural process for investigating materials. Th ...
revealed an unusual magnetic spectrum, and thermal transport revealed chiral
Majorana Fermions
A Majorana fermion (, uploaded 19 April 2013, retrieved 5 October 2014; and also based on the pronunciation of physicist's name.), also referred to as a Majorana particle, is a fermion that is its own antiparticle. They were hypothesised by E ...
when subject to a magnetic field.
Coordination chemistry of hydrated ruthenium trichloride
As the most commonly available ruthenium compound, RuCl
3·''x''H
2O is the precursor to many hundreds of chemical compounds. The noteworthy property of ruthenium complexes, chlorides and otherwise, is the existence of more than one oxidation state, several of which are kinetically inert. All second and third-row transition metals form exclusively low spin complexes, whereas ruthenium is special in the stability of adjacent oxidation states, especially Ru(II), Ru(III) (as in the parent RuCl
3·''x''H
2O) and Ru(IV).
Illustrative complexes derived from "ruthenium trichloride"
*
RuCl2(PPh3)3, a chocolate-colored, benzene-soluble species, which in turn is also a versatile starting material. It arises approximately as follows:
:2RuCl
3·''x''H
2O + 7PPh
3 → 2RuCl
2(PPh
3)
3 + OPPh
3 + 5H
2O + 2HCl
*
Diruthenium tetraacetate chloride
Diruthenium tetraacetate chloride is the coordination polymer with the formula n. A red brown solid, the compound is obtained by the reduction of ruthenium trichloride in acetic acid. The compound has attracted much academic interest because it f ...
, a mixed valence polymer, is obtained by reduction of ruthenium trichloride in acetic acid.
*
2(benzene">C6H6)">benzene.html" ;"title="uCl
2(
C6H6)sub>2 arises from 1,3-Cyclohexadiene">1,3-cyclohexadiene
Cyclohexa-1,3-diene is an organic compound with the formula (C2H4)(CH)4. It is a colorless, flammable liquid. Its refractive index is 1.475 (20 °C, D). A naturally occurring derivative of 1,3-cyclohexadiene is terpinene, a component of pine oi ...
or 1,4-Cyclohexadiene">1,4-cyclohexadiene
1,4-Cyclohexadiene is an organic compound with the formula C6H8. It is a colourless, flammable liquid that is of academic interest as a prototype of a large class of related compounds called terpenoids, an example being γ-terpinene. An isomer of ...
, an intensely luminescent salt with a long-lived excited state, arising as follows:
.