Ferric chloride coordination

Cationic mechanisms are much more characteristic of the polymerization of oxygen heterocycles, both ethers and acetals. A wide variety of catalysts has been used, including protonic acids, such Lewis acids as boron trifluoride, phosphorus pentafluoride, stannic chloride, antimony pentachloride, titanium tetrachloride, zinc chloride, and ferric chloride, and salts of carbocations or tri-alkyloxonium ions having anions derived from Lewis acids. Some complex, coordination catalysts that appear to operate by a mechanism... 

Boduszynski et al. (1980) described an elaborate new separation procedure for isolating and concentrating chemically defined compound types rather than solubility types. A residuum (675°C+) is first fractionated by chromatography with an ion and cation resin to isolate acids and bases, followed by coordination chromatography on ferric chloride Attapulgas clay to separate the remaining neutral Lewis base and hydrocarbon fraction. This latter component is further separated into saturate and aromatic hydrocarbons over silica gel. 

Coordination polymerisation was first proposed in 1956 for the unusual, at that time, low-pressure polymerisation of ethylene and polymerisation of propylene with the transition metal catalysts discovered by Ziegler in 1953 [1], and for the ferric chloride catalysed ring-opening polymerisation of propylene oxide to crystalline polymer reported by Pruitt et al. in a Dow patent [2]. 

The first report on the coordination polymerisation of epoxide, leading to a stereoregular (isotactic) polymer, concerned the polymerisation of propylene oxide in the presence of a ferric chloride-propylene oxide catalyst the respective patent appeared in 1955 [13]. In this catalyst, which is referred to as the Pruitt Baggett adduct of the general formula Cl(C3H60)vFe(Cl)(0C3H6),CI, two substituents of the alcoholate type formed by the addition of propylene oxide to Fe Cl bonds and one chlorine atom at the iron atom are present [14]. A few years later, various types of catalyst effective for stereoselective polymerisation of propylene oxide were found and developed aluminium isopropoxide-zinc chloride [15], dialkylzinc-water [16], dialkylzinc alcohol [16], trialkylalumi-nium water [17] and trialkylaluminium-water acetylacetone [18] and trialkyla-luminium lanthanide triacetylacetonate H20 [19]. Other important catalysts for the stereoselective polymerisation of propylene oxide, such as bimetallic /1-oxoalkoxides of the [(R0)2A10]2Zn type, were obtained by condensation of zinc acetate with aluminium isopropoxide in a 1 2 molar ratio of reactants [20-22]. 

Before that, the mass spectra of some coordination compounds were interpreted in terms of metal valency changes (Shannon and Swan, 1965). Thus, although ferric and auric chloride vapours have similar dimeric structures, the mass spectrum of ferric chloride showed the loss of two... 

The reaction between pheiianthroline and ferric chloride in glacial acetic acid gives the yellow complex Fe(phen)Cl3, which has been formulated to contain six-coordinate iron(III), possibly Fe2(i)hen)2CI(i. The direct reaction between aquo-ferric ions and pheiianthroline gives a brown material containing two iron atoms per molecule, whereas oxidation of the deep red tris(phenanthroline)iron(II) ion affords the pale lilue Fe(III)(phen)3 oii ( )- The brown dimer and related species have been the subject of many investigations (16, 96, 205, 222, 416). They were... 

The coordination catalysts for these reactions are diverse. They can be compounds of alkaline earth metals, like calcium amide, or calcium amide-alkoxide. They can also be Ziegler-Natta-type catalysts. These can be alkoxides of aluminum, magnesium, or zinc combined with ferric chloride. Others are reaction products of dialkylzinc with water or alcohol. They can also be bimetallic //-oxoalkoxides, such as [(RO)2A102]Zn. Other catalysts are aluminum or zinc metalloporphyrin derivatives (see Fig. 4.1). 

Describe the mechanism and write the chemical equations for coordinated anionic polymerizations of propylene oxide by ferric chloride and by diethylzinc-water. Show the reaction mechanism. 

The several ferric chloride complexes existing in solutions containing chloride ion exchange both their coordinated waters and coordinated chloride ions with waters and chloride ions in the bulk of the solution. Under favorable conditions it is possible to ascertain the rates of such exchange reactions by NMR measurements. 

When aluminium trichloride is dissolved in water, the complete replacement of chloride by water molecules with additional coordination of water molecules takes place and polynuclear hydrated is finally found in its solution. Intermediate species, such as [AlClJfoiv., can be detected in phosphorus oxychloride or in phenyl phosphonic dichloride jn the presence of antimony(V) chloride or ferric chloride . Other chloronium ions are formed in solvents of moderate donor number in the presence of a suitable acceptor . 

The features of ferric chloride solutions in phosphorus oxychloride merit some detailed discussion. 5.10 2M solutions are dark red s and contain polymeric oxygen-coordinated species . Amorphous materials are obtained from such solutions after removal of the solvent s. More dilute solutions (c/ lQ- M) are still red with the main species being a monomeric solvated complex, such as Cl3Fe(OPCl3)n apart from solvated cations and probably tetrachloroferrate ions which contribute to the conductivities of such solutions s. From these solutions the compounds Cl3FeOPCl3 and (FeCl3)2(OPCl3)3 have been obtained. On further dilution with phosphorus oxychloride (c M) a yellow colour is produced due to the presence... 

The situation is different in solutions of aluminium chloride in phosphorus oxychloride, deriving from a higher affinity of aluminium chloride towards 0-coordination than in the case of ferric chloride. Polymeric species seem to be present according to the results of precise conductivity measurements , the high surface tensions and high viscosities. Conductometric, potentiometric, spectro-photometric and preparative investigations have shown that aluminium chloride reacts in phosphorus oxychloride and in phenylphosphonic dichloride with considerable formation of autocomplex ions. Chloride ions are released by ionization of aluminium chloride due to preferred 0-coordination by the solvent. These chloride ions may react with other solvate molecules to give the chloro-complex ... 

The higher affinity for 0-coordination of aluminium chloride is responsible for its reaction with ferric chloride, which mainly may be represented for the most part by the equation ... 

The extent of chloride ion transfer reactions has been extensively studied by spectrophotometric techniques. One of the approaches has been based on the pronounced differences in spectra between solvent-coordinated and fully chloride-coordinated ferric chloride in phosphorus oxychlorideio and phenylphosphonic... 

No chloro-coordinated iron(III) species have been identifiedi27,i48,151,152 although Drago and Purcell conclude, from a small increase in absorbance on addition of chloride ions to ferric chloride solutions, that [FeCl]++ should... 

Ferric chloride gives several chloride coordinated species in nitromethanei and phosphorus oxychloridei 20 the species are polymeric at in the... 

The mechanism of the ferric chloride-propylene oxide complex-initiated polymerization has been considered to be a coordinate anionic polymerization in which monomer, propylene oxide, first coordinates with iron, followed by nucleophilic attack of the alkoxide group on one of the oxirane carbons. 

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