Regarding Ruthenium from Humble Beginnings in Siberia, Ruthenium Has Blossomed Into an Incredibly Interesting and Useful Element

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in your element Regarding ruthenium From humble beginnings in Siberia, ruthenium has blossomed into an incredibly interesting and useful element. simon higgins looks at its role in past — and perhaps future — nobel Prize-winning discoveries.

iven its position in the middle of the The compound usually used as a starting Perhaps the most-studied ruthenium d-block of the periodic table, it is not material in ruthenium chemistry, however, complex of recent times has been ′ 2+ Gsurprising that ruthenium exemplifies is ‘hydrated ruthenium trichloride’, an [Ru(2,2 -bipyridine)3] , sometimes many of the properties of the transition almost black, reflective solid that is called rubipy, and its derivatives. metals — such as forming complexes in obtained industrially by dissolving On irradiation with visible light,

a wide range of formal oxidation states RuO4 in aqueous HCl and rubipy produces a long-lived (from viii to –ii). First described in 1844 evaporating to dryness. It is photoexcited triplet, by Karl Klaus, who isolated it from the soluble in a wide range of essentially [RuIII(2,2′-

insoluble residue left on dissolving crude solvents, is comparatively bipyridine)2(2,2′- Siberian platinum in aqua regia, it was reactive, and — despite bipyridine•–)]2+. The

named after Russia (LatinRuthenia ) — its name — mainly Ru(iii) is a strong 27 partly in tribute to Klaus’s homeland and consists of oxo-bridged oxidant, whereas ′ BMM partly in recognition of the earlier efforts dimeric Ru(iv) chloro- the 2,2 -bipyridine h- A j

of Gottfried Osann who had suggested the complexes. radical anion is a N

existence of new elements in these residues, A landmark powerful reductant. ; Be NS

one of which he had named ruthenium. in coordination It was pointed out o

Ruthenium is rare (it comprises roughly chemistry was the in the mid-1970s MM –7 10 % of the Earth’s crust). It is usually 1965 report by Allen that, in principle, Co IA

found together with its five fellow ‘platinum and Senoff of the first this photoexcited ed IM

group’ metals (Os, Rh, Ir, Pd and Pt), but synthetic complexes of state is capable of k I because of the much greater demand for N2, [Ru(NH3)5(N2)]X2 both oxidizing and g/W

rhodium and platinum, ruthenium is (X = anion). These reducing water, to O2 and IN

currently fairly inexpensive (£3.60/$5.60 per were originally made H2 respectively, giving rise to A.W gram). Industrially, it is used as a hardener, by treatment of ‘ruthenium much research. In practice, the in alloys with platinum and palladium for trichloride hydrate’ with hydrazine, system only works in the presence of applications in electrical switching gear. and showed a weak band in their infrared a sacrificial reducing agent and a quencher, –1 Moreover, titanium’s resistance to corrosion spectra at around 2,100 cm , owing to the typically methyl viologen, and gives only H2. can be greatly increased by alloying it with N≡N stretch. Their discovery triggered a More recently, related complexes have small amounts (<1%) of ruthenium. new field — synthetic nitrogen-fixation been much studied as dyes in dye-sensitized A fascinating and sometimes an catalysis — which has produced much solar cells, such as the Grätzel cell. Here, the enigmatic element, the chemistry of new chemistry and insight, but sadly, dye is covalently attached to wide-bandgap ruthenium seems to hold nearly unique no lower-cost rival for the Haber–Bosch semiconductor nanoparticles (usually

charisma in the eyes of its investigators. For process so far. TiO2) that act as an anode, to which the example, in 1984 a magisterial book, The Nowadays, ruthenium is at the forefront photogenerated state transfers an electron. Chemistry of Ruthenium by Seddon and of several important areas of science. For The resulting Ru(iii) is reduced by iodide Seddon, offered complete critical coverage of example, the development of air- and ions in a liquid electrolyte, and the iodine the literature up to 1978; it would be difficult moisture-tolerant homogeneous ruthenium produced is itself re-reduced at a cathode. to envisage a similarly comprehensive catalysts for alkene metathesis has had Such cells are proposed as potential low-cost update today! a major impact in total synthesis and in rivals to silicon solar cells. Together with osmium and xenon, materials chemistry, resulting in a share Over 150 years since ruthenium’s ruthenium exhibits the highest known of the 2005 Nobel Prize in Chemistry for discovery, its chemistry continues to provide formal oxidation state in the periodic their pioneer, Bob Grubbs. Ruthenium fascinating new findings and potential

table — viii — in RuO4. This volatile and complexes are also extensively employed in technologies. No doubt its lure will continue toxic compound, which has an odour of enantioselective hydrogenation reactions to attract others to its study. ❐ ozone if one is foolhardy enough to sniff it, in organic synthesis (exemplified by the

is soluble in CCl4 and is a strong oxidant. work of Ryoji Noyori, who was one of SiMOn HiGGinS is in the Department the winners of the 2001 Nobel Prize in of Chemistry, University of Liverpool, Chemistry), and are now being investigated Liverpool L69 7ZD, UK. in chemotherapy. e-mail: [email protected] Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm 1100 nature chemistry | VOL 2 | DECEMBER 2010 | www.nature.com/naturechemistry