Benzene, chromium complex cobalt complexes

Complexes of butyl vinyl sulfoxide and iron, chromium and cobalt (III) nitrates were found to be unstable, the ferric salt (the least stable) exploding even as a 40 mol% solution in benzene. It is considered that other vinyl sulfoxide ligands will behave similarly. 

Acetylenes are well known to undergo facile trimerizations to derivatives of benzene in the presence of various transition metal catalysts 23). A number of mechanisms for this process have been considered including the intervention of metal-cyclobutadiene complexes 24). This chemistry, however, was subjected to close examination by Whitesides and Ehmann, who found no evidence for species with cyclobutadiene symmetry 25). Cyclotrimeri-zation of 2-butyne-l,l,l-d3 was studied using chromium(III), cobalt(II), cobalt(O), nickel(O), and titanium complexes. The absence of 1,2,3-trimethyl-4,5,6-tri(methyl-d3) benzene in the benzene products ruled out the intermediacy of cyclobutadiene-metal complexes in the formation of the benzene derivatives. The unusual stability of cyclobutadiene-metal complexes, however, makes them dubious candidates for intermediates in this chemistry. Once formed, it is doubtful that they would undergo sufficiently facile cycloaddition with acetylenes to constitute intermediates along a catalytic route to trimers. 

Benzene, benzene-d , and fluorobenzene were found (770, 777) to react with chromium, cobalt, iron, and nickel atoms on codeposition in the neat ligand at 77 K, or in argon matrices at 10-12 K. IR studies of the products indicated that the initial reaction of these transition-metal atoms with an aromatic system is 7r-complex formation. Studies of ligand concentration-effects showed that the chromium-atom reaction is approximately second-order with respect to benzene, yielding the previously known (782) complex (CeH6)2Cr, whereas, with the other metals, the reaction is first-order, yielding MfCsHs), M = Co, Fe, or Ni. The absence of CrfCeH ) is probably a reflection of (a) the fact that the... 

The reaction of the iron-carbene complex [[Bu C CC(OEt)=)Fe(CO)4] with 1,3-cyclohexadiene afforded223 (32), which was characterised by X-ray diffraction. The addition of the anionic derivatives of i-(diphenylmethane)-il-fluorene- and ii-(9,10-dihydroanthracene)-bis tricarbonylchromium to the hydrocarbon moiety (alkene, benzene, cyclohexadienyl, cycloheptadienyl and cycloheptatrienyl) in various cationic compounds of manganese, rhenium, iron, chromium, molybdenum, tungsten and cobalt was reported224 to provide a new route to hydrocarbon-bridged heteronuclear species such as (33). 

Isonitrosobenzoylmethane reacts with iron i salts to yield a blue inner complex salt that is soluble in benzene. One drop of the test solution is placed on filter paper and spotted with a 1 % alcoholic solution of the reagent. When held over ammonia, a green fleck appears Idn. Limit 0.02 y Fe). The test may be conducted likewise on a spot plate or in a micro crucible. In the latter case, benzene extraction is possible. Copper, cobalt, nickel interfere silver, lead, zinc, manganese, chromium lower the sensitivity. 

It is not clear when dithiocarbamates were first prepared, but certainly they have been known for at least 150 years, since as early as 1850 Debus reported the synthesis of dithiocarbamic acids (1). The first synthesis of a transition metal dithiocarbamate complex is also unclear, however, in a seminal paper in 1907, Delepine (2) reported on the synthesis of a range of aliphatic dithiocarbamates and also the salts of di-iTo-butyldithiocarbamate with transition metals including chromium, molybdenum, iron, manganese, cobalt, nickel, copper, zinc, platinum, cadmium, mercury, silver, and gold. He also noted that while dithiocarbamate salts of the alkali and alkali earth elements were water soluble, those of the transition metals and also the p-block metals and lanthanides were precipitated from water, to give salts soluble in ether and chloroform, and even in some cases, in benzene and carbon disulfide. 

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