ruthenium

Ru. Atomic number 44. Electron ^{configuration} [Kr] ^4d75s1 . Group 8 precious metal or platinum group element of the periodic table. Atomic weight 101.07(2). Seven stable isotopes are known: mass numbers 96 (5.54(14)%), 98 (1.87(3)%), 99 (12.76(14)%), 100 (12.60(7)%), 101 (17.06(2)%), 102 (31.55(14)%), and 104 (18.62(27)%). Radioactive isotopes with mass numbers between 87 and 120 are also known. In 1828, G. Osann of Russia claimed to have discovered three new metallic elements other than platinum in platinum minerals, one of which he named after the Latin name for Russia, Ruthenia. However, in 1848, K. K. Klaus of Russia succeeded in isolating it and discovered that the other two were incorrect.
It exists as an alloy with other platinum group elements. Examples of its compounds include laurite (RuS _{2 )} and iridosminite (Ir, Ru, Rh, Pt) AsS. Its abundance is low even among the platinum group elements that are rare in the earth's crust. South Africa has the largest Ru resource because its major deposits, which account for about 90% of the platinum group element reserves, have a high Ru content. After separation of platinum group elements using solvent extraction, it is oxidized to the volatile form of RuO ₄ , which is then distilled and reduced to obtain the metal. It is a silvery-white metal that is hard and brittle. It has a hexagonal close-packed structure. Its melting point is 2310 °C, its boiling point is 3900 °C. Its density is 12.37 g cm ^-3 (20 °C). Its hardness is 6.5. Its first ionization energy is 7.37 eV. Its oxidation state is -2, 0 to 8. Usually it is 2 or 3. When heated in air, it becomes the black oxide RuO ₂ at temperatures above 700 °C. In the absence of oxygen, it is insoluble in aqua regia. It absorbs hydrogen. Ruthenium tetroxide ( ^RuⅧO4 ₎ is a golden-yellow, volatile solid with a melting point of 25.4°C and a boiling point of 40°C. It is a strong oxidizing agent and poses the risk of fire. _The fluorides _range from ^RuⅢF3 to ^RuⅥF6 , _and ^RuⅤF5 is a tetramer ( ^RuⅤF5 ) _{4 that} is a yellow to dark brown solid. _It forms a variety of complex ions with ligands with N as the coordinating atom in oxidation numbers 2 and 3, such as [Ru( _{NH3 ) 6} ] ²⁺ , [Ru( _NH3 ) ₆ ] ³⁺ , [Ru( _NO )(NH3) ₅ ] ³⁺ , and the mixed valence [(NH3) _3RuCl3Ru ( _NH3 ) ₃ ] ²⁺ . The oxidation numbers -2, 0, and 1 are [Ru ^－Ⅱ (CO) ₄ ] ^2－ , [Ru ⁰ (CO) ₅ ], [Ru ^Ⅰ (CO)Cl ₃ ] ^2－, etc.
The complex catalyst of organophosphorus compounds and ruthenium, developed by Ryoji Noyori (awarded the Nobel Prize in Chemistry in 2001), is used in the synthesis of optically active compounds (asymmetric synthesis). The benzylidene complex of ruthenium (Grubbs catalyst), announced in 1995, is an excellent olefin metathesis catalyst that works even in the presence of water, oxygen, alcohol, and sulfur compounds. Platinum-ruthenium alloys are widely used as catalysts (positive electrodes) for fuel cells. The technology developed by IBM Japan in 2001 to suppress thermal fluctuation by sandwiching an extremely thin ruthenium layer between hard disks significantly increased the capacity, and this was succeeded by the next generation perpendicular magnetic recording method, also developed in Japan (Tohoku University-Hitachi). The demand for Ru increased rapidly, accounting for about 70% of the world demand of 40 tons in 2006. [CAS 7440-18-8]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Ru．原子番号44の元素．電子配置[Kr]4d⁷5s¹の周期表8族貴金属または白金族元素．原子量101.07(2)．質量数96(5.54(14)％)，98(1.87(3)％)，99(12.76(14)％)，100(12.60(7)％)，101(17.06(2)％)，102(31.55(14)％)，104(18.62(27)％)の7種の安定同位体と，質量数87～120の放射性同位体が知られている．1828年，ロシアのG. Osannが白金鉱物中に白金以外に3種類の新金属元素を発見したとして，そのうちの一つをロシアのラテン名Rutheniaにちなんで命名したが，1848年にロシアのK.K. Klausが単離に成功し，あとの二つは誤りであることを見いだした．
ほかの白金族元素とともに合金として存在する．化合物としてはラウラ鉱RuS₂，輝イリドスミン鉱(Ir，Ru，Rh，Pt)AsSなど．地殻中の存在度の低い白金族元素中でも存在度が低い．白金族元素の埋蔵量約90％ を占める南アフリカの主要鉱脈のRu含有率が高いので最大のRu資源国は南アフリカである．白金族の溶媒抽出法による分離後，酸化して揮発性のRuO₄の形で蒸留，還元して金属を得る．銀白色の金属で，硬く，もろい．六方最密構造．融点2310 ℃，沸点3900 ℃．密度12.37 g cm^－3(20 ℃)．硬さ6.5．第一イオン化エネルギー7.37 eV．酸化数－2，0～8．通常は2，3．空気中で熱すると700 ℃ 以上で黒色の酸化物RuO₂となる．酸素が存在しないと王水にも不溶．水素を吸蔵する．四酸化ルテニウムRu^Ⅷ O₄は，融点25.4 ℃，沸点40 ℃ の黄金色の揮発性固体．強力な酸化剤で，発火の危険性がある．フッ化物はRu^Ⅲ F₃からRu^Ⅵ F₆まで，Ru^Ⅴ F₅は四量体 (Ru^ⅤF₅)₄ で黄～暗褐色固体．酸化数2，3でNを配位原子とする配位子と [Ru(NH₃)₆]^2＋，[Ru(NH₃)₆]^3＋，[Ru(NO)(NH₃)₅]^3＋，混合原子価の [(NH₃)₃RuCl₃Ru(NH₃)₃]^2＋ など，多様な錯イオンをつくる．酸化数－2，0，1は [Ru^－Ⅱ(CO)₄]^2－，[Ru⁰ (CO)₅]，[Ru^Ⅰ(CO)Cl₃]^2－ など．
野依良治(2001年ノーベル化学賞を受賞)が開発した有機リン化合物とルテニウムの錯体触媒は光学活性化合物の合成(不斉合成)に使われる．1995年に発表されたルテニウムのベンジリデン錯体(Grubbs触媒)は，水，酸素，アルコール，硫黄化合物の存在下でもはたらくすぐれたオレフィンメタセシス触媒である．燃料電池用触媒(正極)に白金ルテニウム合金が広く使用されている．日本IBMが2001年に開発した，ハードディスクに極薄のルテニウム層をはさんで，熱ゆらぎを抑える技術は容量をいちじるしく増大させたが，さらに次の世代のこれも日本(東北大学-日立)で開発された垂直磁気記録方式に引き継がれ，Ruの需要は急増し2006年には世界の需要40 t の約70％ を占めるに至った．[CAS 7440-18-8]

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