Nickelocene

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

TC-Cyclopentadienyl Nickel Complexes. Nickel bromide dimethoxyethane [29823-39-9] forms bis(cydopentadienyl)nickel [1271 -28-9] upon reaction with sodium cyclopentadienide (63). This complex, known as nickelocene, 7T-(C3H3)2Ni, is an emerald-green crystalline sandwich compound, mp 173°C, density 1.47 g/cm. It is paramagnetic and slowly oxidi2es in air. A number of derivatives of nickelocene are known, eg, methylnickelocene [1292-95-4], which is green and has mp 37°C, and bis( 7t-indenyl)nickel [52409-46-8], which is red, mp 150°C (87,88). 

Substituted derivatives of nickelocene, where one ring has been replaced, include the complex cyclopentadienyl nitrosyl nickel [12071 -73-7], (7T-C3H3)NiNO, a red Hquid, mp -41°C. A review of nitrosyl complexes with nickel is available (89). The dimer complex... 

The sandwich compounds, feiTocene and nickelocene, FefCg 115)2 and Ni(C5H5)2, so called because die metal atom is sandwiched between the organic radicals, C5H5, have also been used to prepare iron and nickel deposits. 

Nickelocene [bis-(cyclopentadienyl)nickel II] [1271-28-9] M 188.9, m 173-174 (under N2). Dissolve in Et20, filter and evaporate in a vacuum. Purify rapidly by recrystn from pet ether using a solid C02-Me2C0 bath, m 171-173°(in an evacuated tube). Also purified by vacuum sublimation. [J Am Chem Soc 76 1970 954 J Inorg Nud Chem 2 95, 110 7956.]... 

Dimesitylimidazolium chloride with nickelocene gives the carbene complex [(T) -Cp)NiCl(L)] (L= l,3-dimesitylimidazol-2-ylidene), in which the chloride ligand can be substituted by a methyl group by reacting the product with methyl-lithium (OOJOM(596)3). 

Cobaltocene and nickelocene were studied by Wheeler and McClin . Retention of Ni in nickelocene was about 65%, and increased to 92% on annealing at 100 °C for one hour. Nickelocinium ion was formed to... 

Further work on nickelocene and cobaltocene was done by Ross , who synthesized the respective compounds using Ni, Ni and " Co, which decay be E.C., jS and a fully converted isomeric transition, respectively, all producing radioactive cobalt isotopes. The results showed retentions, after sublimation, of 84%, 83% and 80%, respectively. The composition of the unsublimable residue was largely CoCp2, except for the highly converted "Co, where only 30% CoCpj could be detected. This was interpreted as showing that by internal conversion the molecules are totally destroyed, by the same sort of argument as was used by Riedel and Merz . 

Evidence for slow inversion at nitrogen in the compound (106) and its tetrachloro analogue has been obtained 142>. The adduct of tetra-fluorobenzyne with cyclopentadiene has been obtained but of rather more interest is the isolation of the isomeric adducts (108) and (109) from the reaction of tetrafluorobenzyne with nickelocene 143>. No adducts were obtained from attempted reactions with ferrocene 144 80). 

Explosively polymerises when heated >110°C in presence of nickelocene catalyst. 

B = 408 cm-1, (J3 = 0.44), and C/B = 8.84. The C/B ratio deduced is markedly greater than that customarily used, and it was partly upon this interpretation of the ferrocene spectrum that Cerny, Pavlik, and Maxova (44, 45) based their use of C/B values greater than 4.0 in interpreting the spectra of vanadocene and nickelocene. 

As an example the calculation of the g values for the ds, 32 (a2 it2 S4) ground state of nickelocene may now be outlined, using the hole-equivalent d2 wave functions. It is... 

Nickelocene 27 mg Ni/kg BW Nickel oxide >744 mg/kg BW Nickel perchlorate heptahydrate ... 

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