A metallocene is a compound consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are used industrially. Cationic group 4 metallocene derivatives related to + catalyze olefin polymerization; some metallocenes consist of metal plus two cyclooctatetraenide anions, namely the lanthanocenes and the actinocenes. Metallocenes are a subset of a broader class of compounds called sandwich compounds. In the structure shown at right, the two pentagons are the cyclopentadienyl anions with circles inside them indicating they are aromatically stabilized. Here they are shown in a staggered conformation; the first metallocene to be classified was ferrocene, was discovered in 1951 by Kealy and Pauson, Miller et al. Kealy and Pauson were attempting to synthesize fulvalene through the oxidation of a cyclopentadienyl salt with anhydrous FeCl3 but obtained instead the substance C10H10Fe At the same time, Miller et al reported the same iron product from a reaction of cyclopentadiene with iron in the presence of aluminum, potassium, or molybdenum oxides.
The structure of "C10H10Fe" was determined by Fischer et al.. These two were awarded the Nobel Prize in Chemistry in 1973 for their work on sandwich compounds, including the structural determination of ferrocene, they determined that the carbon atoms of the cyclopentadienyl ligand contributed to the bonding and that bonding occurred due to the metal d-orbitals and the π-electrons in the p-orbitals of the Cp ligands. This complex is now known as ferrocene, the group of transition metal dicyclopentadienyl compounds is known as metallocenes. Metallocenes have the general formula. Fischer et al. First prepared the ferrocene derivatives involving Ni. Derived from substituted derivatives of cyclopentadienide, metallocenes of many elements have been prepared. One of the earliest commercial manufacturers of metallocenes was Arapahoe Chemicals in Boulder, Colorado The general name metallocene is derived from ferrocene, 2Fe or Cp2Fe, systematically named bisiron. According to the IUPAC definition, a metallocene contains a transition metal and two cyclopentadienyl ligands coordinated in a sandwich structure, i.e. the two cyclopentadienyl anions are on parallel planes with equal bond lengths and strengths.
Using the nomenclature of "hapticity", the equivalent bonding of all 5 carbon atoms of a cyclopentadienyl ring is denoted as η5, pronounced "pentahapto". There are exceptions, such as uranocene, which has two cyclooctatetraene rings sandwiching a uranium atom. In metallocene names, the prefix before the -ocene ending indicates what metallic element is between the Cp groups. For example, in ferrocene, ferrous iron is present. In contrast to the more strict definition proposed by IUPAC, which requires a d-block metal and a sandwich structure, the term metallocene and thus the denotation -ocene, is applied in the chemical literature to non-transition metal compounds, such as barocene, or structures where the aromatic rings are not parallel, such as found in manganocene or titanocene dichloride; some metallocene complexes of actinides have been reported where there are three cyclopendadienyl ligands for a monometallic complex, all three of them bound η5. There are many –metal complexes and they can be classified by the following formulas: Metallocene complexes can be classified by type: Parallel Multi-decker Half-sandwich compound Bent metallocene or tilted More than two Cp ligands Three main routes are employed in the formation of these types of compounds: Sodium cyclopentadienide is the preferred reagent for these types of reactions.
It is most obtained by the reaction of molten sodium and dicyclopentadiene. Traditionally, the starting point is the cracking of dicyclopentadienyl, the dimer of cyclopentadiene. Cyclopentadiene is deprotonated by strong bases or alkali metals. MCl2 + 2 NaC5H5 → 2M + 2 NaCl CrCl3 + 3 NaC5H5 → + 1⁄2 "C10H10" + 3 NaClNaCp acts as a reducing agent and a ligand in this reaction; this technique provides using metal atoms in the gas phase rather than the solid metal. The reactive atoms or molecules are generated at a high temperature under vacuum and brought together with chosen reactants on a cold surface. M + C5H6 → MC5H5 + 1⁄2 H2 M + 2 C5H6 → + H2 A variety of reagents have been developed that transfer Cp to metals. Once popular was thallium cyclopentadienide, it reacts with metal halides to give thallium chloride, poorly soluble, the cyclopentadienyl complex. Trialkyltin derivatives of Cp− have been used. Many other methods have been developed. Chromocene can be prepared from chromium hexacarbonyl by direct reaction with cyclopentadiene in the presence of diethylamine.
Cr6 + 2 C5H6 → Cr2 + 6 CO + H2Metallocenes have high thermal stability. Ferrocene can be sublimed in air at over 100 °C with no decomposition. Industrially, sublimation is not practical so metallocenes are isolated by crystallization or produced as part of
The Brazilian Ice Sports Federation was founded by Eric Maleson, Brazil's first bobsled athlete. The CBDG was established in 1996 and affiliated to the Brazilian Olympic Committee in 1999; the federation qualified 7 athletes for the 2002 Winter Olympics in Salt Lake City, Utah and a 4-man bobsled team for the 2006 Winter Olympics in Torino. The federation is responsible for the development of all winter Olympic ice sport modalities for Brazil including bobsled, luge, long track and short track speed skating and ice hockey; the Brazilian Ice Sports Federation made curling history in August 2008 when they challenged the United States for a berth at the World Curling Championship. This was the first time any South American team has offered a challenge to the United States for a berth in the World Curling Championship; the players involved trained in Lennoxville and included Luis Silva, Marcelo De Mello, Celso Kossaka and Cesar Santos. See 2009 USA-Brazil Challenge; the Brazilian team were unsuccessful.
Men's national team National inline hockey team 2017 IIHF profile CBDG official website
Alexander Ankvab, a President of Abkhazia from 2011 to 2014, has survived six assassination attempts since becoming Prime Minister in 2005. Two weeks after having been appointed Prime Minister, Alexander Ankvab's car was fired upon in the evening of 28 February 2005; the car was hit by 17 bullets, but Ankvab was not harmed as he was traveling in the car of his Vice-Premier Leonid Lakerbaia. No injuries were reported. Newly elected President Sergei Bagapsh blamed the attack on "criminal elements" opposed to reform "who do not want to live in accordance to the law”. On 1 March, Ankvab ordered Interior Minister Otar Khetsia to crack down on criminal gangs, blaming the assassination attempt on people discontent with his decision to raise the taxes on the export of scrap metal. On 1 April, Ankvab's car was attacked again, near Sukhumi. Neither he nor Vice-Premier Lakerbaia was injured; the next day, the Interior Ministry offered a reward of 5000 dollars for information that would lead to the capture of the perpetrators.
Interior Minister Otar Khetsia, declared that "the same forces", behind the assassination attempt on 28 February were responsible. Head of the criminal investigation Jamal Gogia announced on 7 April that his team was considering three possible backgrounds for the organisers of the attack: corrupt businessmen unhappy with tighter government control, criminals dissatisfied with the announced step-up in crime fighting and the Georgian or some other special service wanting to destabilise Abkhazia. On 20 June, during a remote-control bomb detonated during a thunderstorm near New Athos. On 27 June, a group of academics and journalists released a statement in which they claimed that it was known the bomb had been aimed at Alexander Ankvab and that it was immoral and dangerous to keep silent about it. On July 9, 2007, Ankvab and his driver were injured when the back of their vehicle was fired upon from a grenade cup discharger near Gudauta, on the road to Sukhumi. Ankvab stated. President Bagapsh cut short a visit to Moscow after the attack.
He blamed people opposed to reforms and the fight against organised crime for the attack, added on 10 July that the attack was political in nature and not a settling of scores between criminals. He warned the leadership of the law enforcement agencies that they would be fired if results were not obtained within two weeks, stated that the attack was a logical result of the agencies' failure to resolve the previous assassination attempts; the People's Assembly of Abkhazia called upon the government to timely investigate the attack and accused "destructive forces active both inside and outside Abkhazia" of trying to destabilize the situation in Abkhazia. The Interior Ministry proclaimed a 500,000-ruble reward for information leading to the capture of the attackers. Georgian MP Konstantine Gabashvili accused the Russian special services of trying to get rid of Ankvab because he had suggested reexamining all illegal real estate transactions in Abkhazia, including those involving Russian companies.
On 16 July, Ankvab denied having given an interview to the Tbilisi-based newspaper Svobodnaya Gruzya, in which he accused the Georgian Ministry of Internal Affairs of being involved in the assassination attempts, condemned the publication as unethical. On 2 August, President Bagapsh announced that there was serious progress in the investigation, but cautioned that the investigation should be conducted and scrupulously, that everything needed to be proven with "150%" certainty. Alexander Ankvab was elected Vice-President in December 2009 along with President Bagapsh. On 23 September 2010, 2:15 am local time, a grenade was fired at Ankvab's house in Gudauta from a RPG-26 launcher. Ankvab received non-life-threatening injuries to his leg. According to Deputy Chief Prosecutor Beslan Kvitsinia, the attack was related to Ankvab's work in government. On 29 May 2011, President Bagapsh died and Ankvab contested the subsequent Presidential election. According to prosecutors, an attack was planned on Ankvab during the 17 August 2011 meeting with voters in Alakhadzykh, Gagra District.
According to prosecutors, an attack was staged on Ankvab in November 2011, in the Gudauta District village of Primorskoe, on the road to Aatse. The attack was aborted. According to prosecutors, the same people tried to kill Ankvab in January 2012 by letting a bomb explode in the Gudauta District village of Kulanyrkhua, but the bomb did not go off as planned. On 22 February 2012, Ankvab survived a mine and gun attack on his convoy in Kulanyrkhua, on the road from Gudauta to Sukhumi, which killed two of his guards. On 12 April, six suspects were arrested for the assassination attempt in February, including well-known businessman Anzor Butba. Two were released while the remaining four were brought before court on 14 April, receiving 2 months of pre-trial detention. On 17 April, police attempted to arrest former Interior Minister and Vice Presidential candidate Almasbei Kchach at his home in Gagra, but found him dead in an apparent suicide by firearm; the same day, police arrested Murtaz Sakania in the village of Khypsta, Gudauta District.
Khypsta received no life-threatening injuries from the act. In the night from 17 to 18 April, one of the original suspects in pre-trial detention, Timur Khutaba, hanged himself in his prison cell. On 20 April, the Sukhumi court issued pre-trial detention to Murtaz Sakania and the Supreme Court board of appeal confirmed the pre-trial detention of Anzor Butba; the lawyers o