44
  Ru  
101.070000
Ruthenium

Name: Ruthenium
Symbol: Ru
Atomic Number: 44
AtomicWeight: 101.070000
Family: Transition Metals
CAS RN: 7440-18-8
Description: Rare hard brittle silvery metal, which is unaffected by air water and acids, but is dissolved by molten alkalis.
State (25C): Solid
Oxidation states: +1, 2, +3, +4, +6, +8

Molar Volume: 8.22 cm3/mole
Valence Electrons: 4d75s

Boiling Point:  4173K, 3900C, 7052F
Melting Point:
2523K, 2250C, 4082F
Electrons Energy Level: 2, 8, 18, 15, 1
Isotopes: 27 + 7 Stable
Heat of Vaporization: 595 kJ/mol
Heat of Fusion: 24 kJ/mol
Density: 12.37 g/cm3 @ 300K
Specific Heat: 0.238 J/gK
Atomic Radius: 1.89
Ionic Radius: 0.68
Electronegativity: 2.2 (Pauling); 1.42 (Allrod Rochow)
Vapor Pressure: 1.4 Pa @ 2250C

1s2 2s2p6 3s2p6d10 4s2p6d7 5s1

History

Ruthenium was discovered and isolated by Russian scientist Karl Karlovich Klaus in 1844.  Klaus showed that ruthenium oxide contained a new metal and obtained 6 grams of ruthenium from the part of crude platinum that is insoluble in aqua regia.

Jons Jakob Berzelius and Gottfried Osann nearly discovered ruthenium in 1827.  The men examined residues that were left after dissolving crude platinum from the Ural Mountains in aqua regia.  Berzelius did not find any unusual metals, but Osann thought he found three new metals and named one of them ruthenium.

The name derives from Ruthenia the Latin word for Russia, a historical area which includes present day Ukraine, Belarus, and parts of the Russia, Baltics, Slovakia and Poland.  Karl Klaus called the element in honour of his birthland.  He was born in Tartu, Estonia.

It is also possible that Polish chemist Jedrzej Sniadecki isolated element 44 (which he called vestium) from platinum ores in 1807.  However his work was never confirmed and he later withdrew his discovery claim.

Characteristics

A polyvalent hard white metal, ruthenium is a member of the platinum group, has four crystal modifications and does not tarnish at normal temperatures, but does oxidize explosively.  Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by halogens at high temperatures.  Small amounts of ruthenium can increase the hardness of platinum and palladium.  The Corrosion resistance of titanium is increased markedly by the addition of a small amount of ruthenium.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d7
5s1

This metal can be plated either through electrodeposition or by thermal decomposition methods.  One ruthenium-molybdenum alloy has been found to be superconductive at 10.6oK.   The oxidation states of ruthenium range from +1 to +8, and -2 is known, though oxidation states of +2, +3, and +4 are most common.

Occurrence

This element is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America.  Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario, Canada and in pyroxenite deposits in South Africa.

This metal is commercially isolated through a complex chemical process in which hydrogen is used to reduce ammonium ruthenium chloride yielding a powder.  The powder is then consolidated by powder metallurgy techniques or by argon-arc welding.

It is also possible to extract ruthenium from spent nuclear fuel, which contains an average of 2 kg of ruthenium per metric ton. Ruthenium produced in such a way contains radioactive isotopes, some with a half-life of up to 373.59 days.  Therefore this ruthenium has to be stored at least for 10 years in a secured area to allow it to become stable.  Fission-derived ruthenium has a specific activity of 8.1 curies of radioactivity per gram.  Under health physics safety rules any isotope that emits more than 1 ci of activity is a hazard; however, after 6 years the activity falls to 4.1 ci, after 7 years it is 2.2, after 8 years 1.1, after 9 years .55 ci and after 10 years only .27 ci.  After 20 years the activity falls to 2.702E-4 ci, which is under the threshold for low level risk by even the most stringent health physics rules.

Applications

Due to its highly effective ability to harden platinum and palladium, ruthenium is used in Pt and Pd alloys to make severe wear-resistant electrical contacts.  It is sometimes alloyed with gold in jewelry.

Ruthenium is also a versatile catalyst: hydrogen sulfide can be split by light by using an aqueous suspension of CdS particles loaded with ruthenium dioxide.  This may be useful in the removal of H2S from oil refineries and from other industrial processes.

Organometallic ruthenium carbene and allenylidene complexes have recently been found as highly efficient catalysts forolefin metathesis with important applications in organic and pharmaceutical chemistry.

Recently, large metallo-organic complexes of ruthenium have been found to exhibit anti-tumor activity and the first of a new group of anti-cancer medicine are now in the stage of clinical trials.

Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched in various, potential, solar energy technologies.

Ruthenium will also be used in some advanced high-temperature single-crystal superalloys, with applications including the turbine blades in jet engines.

Ruthenium red, [(NH3)5Ru-O-Ru(NH3)4-O-Ru(NH3)5]6+, is a biological stain used to visualize polyanionic areas of membranes.

Ruthenium-centered complexes are being researched for possible anticancer properties.   Ruthenium, unlike traditional platinum complexes, show greater resistance to hydrolysis and more selective action on tumors.  NAMI-A and KP1019 are two drugs undergoing clinical evaluation against metastatic tumors and colon cancers.

Fountain pen nibs are frequently tipped with alloys containing ruthenium. From 1944 onward, the famous Parker 51 fountain pen was outfitted with the "RU" nib, a 14K gold nib tipped with 96.2% ruthenium, 3.8% iridium.

Compounds

Ruthenium compounds are often similar in properties to those of osmium and exhibit at least eight oxidation states, but the +2, +3, and +4 states are the most common.   Examples are ruthenium (IV) oxide (Ru(IV)O2, oxidation state +4), dipotassium ruthenate (K2Ru(VI)O4, +6), potassium perruthenate (KRu(VII)O4, +7) and ruthenium tetroxide (Ru(VIII)O4, +8). Compounds of ruthenium with chlorine are ruthenium (II) chloride (RuCl2) and ruthenium (III) chloride (RuCl3).

Ruthenium (II) Chloride, RuCl2 Ruthenium (III) Chloride, RuCl3
Ruthenium (IV) Oxide, RuO2 Dipotassium (VI) Ruthenate,  K2RuO4
Potassium (VII) Perruthenate, KRuO4 Ruthenium (VIII) Tetroxide, RuO4

Organometallic Chemistry

It is quite easy to form compounds with carbon ruthenium bonds, these compounds tend to be darker and react more quickly than the osmium compounds.  Recently Prof Tony Hill and his co-workers have been making compounds of ruthenium in which a boron atom binds to the metal atom.

The organometallic  ruthenium compound that is easiest to make is RuHCl(CO)(PPh3)3.   This compound has two forms (yellow and pink) that are identical once they are dissolved but different in the solid state.

An organometallic compound similar to ruthenocene, bis(2,4-dimethylpentadienyl)ruthenium, is readily synthesized in near quantitative yields and has applications in vapor-phase deposition of metallic ruthenium, as well as in catalysis, including Fischer-Tropsch synthesis of transportation fuels.

Important catalysts based on ruthenium are Grubbs' catalyst and Roper's complex.

Isotopes

Naturally occurring ruthenium is composed of seven isotopes.  The most stable radioisotopes are 106Ru with a half-life of 373.59 days, 103Ru with a half-life of 39.26 days and 97Ru with a half-life of 2.9 days.

Twenty-seven other radioisotopes have been characterized with atomic weights ranging from 86.9 amu (87Ru) to 119.9 (120Ru).  Most of these have half-lives that are less than five minutes except 95Ru (half-life: 1.643 hours) and 105Ru (half-life: 4.44 hours).

The primary decay mode before the most abundant isotope, 102Ru, is electron capture and the primary mode after is beta emission.  The primary decay product before 102Ru is technetium and the primary mode after is rhodium.

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
87Ru 86.94918 ~50 ms
88Ru 87.94026 1.3 seconds
89Ru 88.93611 1.38 seconds
90Ru 89.92989 11.7 seconds
91Ru 90.92629 7.9 seconds
92Ru 91.92012 3.65 minutes
93Ru 92.91705 59.7 seconds
94Ru 93.911360 51.8 minutes
95Ru 94.910413 1.643 hours
96Ru 95.907598 Stable
97Ru 96.907555 2.791 days
98Ru 97.905287 Stable
99Ru 98.9059393 Stable
100Ru 99.9042195 Stable
101Ru 100.9055821 Stable
102Ru 101.9043493 Stable
103Ru 102.9063238 39.26 days
104Ru 103.905433 Stable
105Ru 104.907753 4.44 hours
106Ru 105.907329 373.59 days
107Ru 106.90991 3.75 minutes
108Ru 107.91017 4.55 minutes
109Ru 108.91320 34.5 seconds
110Ru 109.91414 11.6 seconds
111Ru 110.91770 2.12 seconds
112Ru 111.91897 1.75 seconds
113Ru 112.92249 0.80 seconds
114Ru 113.92428 0.53 seconds
115Ru 114.92869 740 ms
116Ru 115.93081 ~400 ms
117Ru 116.93558 ~300 ms
118Ru 117.93782 ~200 ms
119Ru 118.94284 ~170 ms
120Ru 119.94531 ~80 ms

Precautions

40px-Skull_and_crossbones.svg.jpg (1420 bytes) The compound ruthenium tetroxide, RuO4, similar to osmium tetroxide, is highly toxic and may explode.  Ruthenium plays no biological role but does strongly stain human skin, may be carcinogenic and bio-accumulates in bone. 80px-Flammable.jpg (2186 bytes)

atom.gif (700 bytes)

Ruthenium Data
 

Atomic Structure

  • Atomic Radius: 1.89
  • Atomic Volume:8.3cm3/mol
  • Covalent Radius: 1.25
  • Cross Section (Thermal Neutron Capture) Barns: 2.56
  • Crystal Structure: Hexagonal
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d7 5s1
  • Electrons per Energy Level: 2, 8, 18, 15, 1
  • Ionic Radius: 0.68
  • Filling Orbital: 4d7
  • Number of Electrons (with no charge): 44
  • Number of Neutrons (most common/stable nuclide): 57
  • Number of Protons: 44
  • Oxidation States: 2, 3, 4, 6, 8
  • Valence Electrons: 4d7 5s1

Chemical Properties

  • Electrochemical Equivalents: 1.257 g/amp-hr
  • Electron Work Function: 4.71eV
  • Electronegativity: 2.2 (Pauling); 1.42 (Allrod Rochow)
  • Heat of Fusion: 24 kJ/mol
  • Incompatibilities:
  • Ionization Potential
    • First: 7.37
    • Second: 16.76
    • Third: 28.47
  • Valence Electron Potential (-eV): 64

Physical Properties

  • Atomic Mass Average: 101.07
  • Boiling Point: 4173K, 3900C, 7052F
  • Coefficient of Lineal Thermal Expansion/K-1: 9.1E-6
  • Conductivity
    Electrical: 0.137 106/cm
    Thermal: 1.17 W/cmK
  • Density: 12.37 g/cm3 @ 300K
  • Description:
    Rare hard brittle silvery metal, which is unaffected by air water and acids, but is dissolved by molten alkalis.
  • Elastic Modulus:
    • Bulk: 286/GPa
    • Rigidity: 173/GPa
    • Youngs: 432/GPa
  • Enthalpy of Atomization: 603 kJ/mole @ 25C
  • Enthalpy of Fusion: 25.5 kJ/mole
  • Enthalpy of Vaporization: 567.8 kJ/mole
  • Flammablity Class:
  • Freezing Point: see melting point
  • Hardness Scale
    • Brinell: 2160 MN m-2
    • Mohs: 6.5
  • Heat of Vaporization: 595 kJ/mol
  • Melting Point: 2523K, 2250C, 4082F
  • Molar Volume: 8.22 cm3/mole
  • Physical State (at 20C & 1atm): Solid
  • Specific Heat: 0.238 J/gK
  • Vapor Pressure: 1.4 Pa @ 2250C

Regulatory / Health

  • CAS Number
    • 7440-18-8
  • OSHA Permissible Exposure Limit (PEL)
    • No limits set by OSHA
  • OSHA PEL Vacated 1989
    • No limits set by OSHA
  • NIOSH Recommended Exposure Limit (REL)
    • No limits set by NIOSH
  • Levels In Humans:
    Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
    • Blood/mg dm-3: n/a
    • Bone/p.p.m: n/a
    • Liver/p.p.m: n/a
    • Muscle/p.p.m: n/a
    • Daily Dietary Intake: n/a
    • Total Mass In Avg. 70kg human: n/a
  • Discovery Year: 1808
  • Name Origin:
    From Ruthenia Latin name of Russia.
  • Abundance:
    • Earth's Crust/p.p.m.: 0.001
    • Seawater/p.p.m.: N/A
    • Atmosphere/p.p.m.: N/A
    • Sun (Relative to H=1E12): 67.6
  • Sources:
    Found in pentlandite and pyroxinite. Produced as a by-product of nickel refining. Around 0.12 tons are produced world wide on an annual basis. Primary mining areas are South Africa, Russia, Canada, USA and Zimbabwe.
  • Uses:
    Used to harden platinum and palladium. Also used in eye treatments, thickness meters for egg shells, fountain pen points, and electrical contacts. Aircraft magnetos use platinum alloy with 10% ruthenium.
  • Additional Notes:
    Some sources credit G.W. Osann of discovering ruthenium at the University of Tartu Russia in 1928, but this is was really only a "rediscovery".

Ionization Energy (eV): 7.361 eV
Estimated Crustal Abundance: 110-3 milligrams per kilogram
Estimated Oceanic Abundance:
710-7 milligrams per liter

Transition Metals
Group 3
(IIIB)
4
(IVB)
5
(VB)
6
(VIB)
7
(VIIB)
8
(VIIIB)
9
(VIIIB)
10 (VIIIB) 11
(IB)
12
(IIB)
Period 4 21
Sc
44.95
22
Ti
47.86
23
V
50.94
24
Cr
51.99
25
Mn
54.93
26
Fe
55.84
27
Co
58.93
28
Ni
58.69
29
Cu
63.54
30
Zn
65.39
Period 5 39
Y
88.90
40
Zr
91.22
41
Nb
92.90
42
Mo
95.94
43
Tc
98.00
44
Ru
101.0
45
Rh
102.9
46
Pd
106.4
47
Ag
107.8
48
Cd
112.4
Period 6 57
La
138.9
72
Hf
178.4
73
Ta
180.9
74
W
183.8
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.0
79
Au
196.9
80
Hg
200.5
Period 7 89
Ac
227.0
104
Rf
261.0
105
Db
262.0
106
Sg
266.0
107
Bh
264.0
108
Hs
269.0
109
Mt
268.0
110
Ds
269.0
111
Rg
272.0
112
Uub
277.0