Iodide abstraction

In order to more fully understand the mechanism for the promotion of carbonylation in the Cativa process, a recent comprehensive study utilizing spectroscopic methods and ab initio calculations was carried out to explore the role of the promoters. The acceleration of the migratory insertion step is the result of iodide abstraction from the iridium center in c,m-[fr(CO)2l3Me] by the promoters to yield the neutral species [Ir(CO)3l2Me] in the presence of CO. It was determined that the migratory insertion of carbon monoxide in [fr(CO)3l2Me] is 700 times faster than for the anionic species [fr(CO)2l3Me]. ... 

V.L. Cherginets and V.V Banik, Acidic Properties of Sodium Vanadate and Sodium Tetraborate in Molten Sodium Iodide (Abstract of the 10th All-Union Conference on Physics Chemistry and Electrochemistry of Ionic Melts and Solid Electrolytes, Ekaterinbourg, Vol. 1. 1992) p. 85. 

The iodide-abstraction reaction of [ Rh(/i-I)(/i-RNNNR)2(CO)(bipy) 2][PF6]2 (bipy = 2,2 -bipyridyl, R=/)-tolyl) with AgPFe in MeCN gave [Rh2(CO)(NCMe)2(bipy)(/r-RNNNR)2][PF6]2 which slowly decarbonylated at room temperature to [Rh2(NCMe)3(bipy)(/r-RNNNR)2][PF6]2." " The molecular structures of a series of dirhodium carbonyl complexes with local planar symmetry about each rhodium atom were extensively studied. Different bridging N-N IS and N-0 16 ligands support the dimetallic structures." Many such complexes are long known,but a complete molecular orbital analysis has been described. 

Iodide abstraction by silver salts from the complex 77 77 -CsH4(CH2)2PPh2 Rhl2 yielded products whose structures depend on the coordinating ability of the anion originally associated with silver. Silver trifluoroacetate gave fully... 

The mechanism of iodide abstraction from [FeI(CO)2( n Cp)] by silver tetrafluoroborate has been investigated by NMR spectroscopy for CDCI3 solutions and by IR methods for both CHCI3 and CH2CI2 solutions. It was... 

Complexes C3 have been used as pre-catalysts for the cycloisomerization of a model 1,6-enyne which contains a tosylamide function in the tethering chain (Fig. 10.43). The catalytically active species was generated by iodide abstraction from C3 by addition of a silver salt (AgBp4). The reaction affords the expected 3-azabicyclo[4.1.0]heptene derivative. An extensive catalytic screening highlighted (S. S -Chiraphos as the most effective chiral diphosphine and demonstrated that suitable modulation of the NHC ligand allows increasing of the... 

Strike couldn t find any decent nitroethane synths except for a couple of Chemical Abstract articles. One suggestion is to treat 1.5 moles of Na2C02 with 1 mole of sodium ethylsulfite and 0.0645 moles of K2CO3 at 125-130°C. Another route would be to use silver nitrate and ethyl iodide [8 p119]. This type of reaction has been used to nitrate other paraffins and would probably work. 

Various reducing agents, eg, hydrogen iodide, can abstract chlorine from sulfur monochloride leaving elemental sulfur ... 

Base-catalyzed proton abstraction from trimethylsulfoxonium halides (1) with formation of dimethylsufoxonium methylide (2) was described by Corey in 1962. Solutions of (2) in dimethyl sulfoxide are conveniently prepared from the chloride or iodide (1) by stirring with one equivalent of sodium hydride at room temperature. 

Packer et al. (1981) found that y-irradiation reduces arenediazonium tetrafluoro-borates to aryl radicals. Packer and Taylor (1985) investigated the y-irradiation of 4-chlorobenzenediazonium tetrafluoroborate by a 60Co source in the presence of 1 alone or I- +13 . The major product in the presence of iodide was 4,4 -dichloroazo-benzene. With I- + 1 ", however, it was 4-chloroiodobenzene. Two other investigations of the reactivity of aryl radicals with iodine-containing species are important for the understanding of the chain process of iodo-de-diazoniation that starts after formation of the aryl radical. Kryger et al. (1977) showed that, in the thermal decomposition of phenylazotriphenylmethane, the rate of iodine abstraction from I2 is extremely fast (see also Ando, 1978, p. 341). Furthermore, evidence for the formation of the radical anion V2 was reported by Beckwith and Meijs (1987) and by Abey-wickrema and Beckwith (1987) (see Sec. 10.11). 

On the basis of all these results and his own investigations on chloro- and bromo-de-diazoniations (Galli, 1981), Galli proposed in 1988 that iodo-de-diazoniation, after formation of the aryl radical in the initiation reaction (Scheme 10-22) follows three coupled iodination chain reactions based on the formation of the I2 molecule and the If anion in the step shown in Scheme 10-23, namely iodine atom (I ) addition (Scheme 10-24), and iodine abstraction from I2 and If in Schemes 10-25 and 10-26 respectively. Aryl radicals and iodine molecules are regenerated as indicated in Scheme 10-27. The addition of iodide ion to aryl radicals forming the radical anion [Arl] -, as in Scheme 10-28, is considered an unlikely pathway, as that reaction has been found to be reversible (Lawless and Hawley, 1969 Andrieux et al. 1979). 

Aryl diazonium ions are converted to iodides in high yield by reaction with iodide salts. This reaction is initiated by reduction of the diazonium ion by iodide. The aryl radical then abstracts iodine from either I2 or I3. A chain mechanism then proceeds... 

The complex also undergoes a variety of addition reactions with reagents such as methyl iodide, hydrochloric acid, benzoyl chloride, and allyl chloride.8 In a reaction similar to that of the decarboxylation of aldehydes, the complex will abstract CS from carbon disulfide to give the irans-thiocarbonyl complex rans-RhClCS[P(C8H6)5]2.9... 

This catalytic cycle, generating acetyl iodide from methyl iodide, has been demonstrated by carbonylation of anhydrous methyl iodide at 80°C and CO partial pressure of 3 atm using [(C6H5)4As][Rh(CO)2X2] as catalysts. After several hours reaction, acetyl iodide can be identified by NMR and infrared techniques. However, under anhydrous conditions some catalyst deactivation occurs, apparently by halogen abstraction from the acetyl iodide, giving rhodium species such as frans-[Rh(CO)2I4] and [Rh(CO)I4] . Such dehalogenation reactions are common with d8 and d10 species, particularly in reactions with species containing weak... 

Triethylborane in combination with oxygen provides an efficient and useful system for iodine atom abstraction from alkyl iodide, and thus is a good initiator for iodine atom transfer reactions [13,33,34]. Indeed, the ethyl radical, issued from the reaction of triethylborane with molecular oxygen, can abstract an iodine atom from the radical precursor to produce a radical R that enters into the chain process (Scheme 13). The iodine exchange is fast and efficient when R is more stable than the ethyl radical. 

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