Chloro dimer

Polynuclear anion-bridged complexes. The complex cations [(NHjl CoCp-NH2)(p-RC02)Co(NH3)4] (R = H or Me) have been prepared from the corresponding p-amido-p-chloro-dimer. The dinuclear cation (109) and its deprotonated analogue have been isolated, as have the related cations [(NH,) -... 

Mn(II)-Cl-Mn(n) to Mn(III)-0-Mn(in) + H2O + Cl", followed by re-reduction to the starting oxidation state + O2 + H2O. These reactions are spontaneous and auto-catalytic. The dimanganese site promotes catalysis by stabilizing the bridging X-oxo over the i-chloro structure by 0.15-0.38 V vs NHE. H2O2 cannot oxidize the p.-chloro dimer without i-oxo formation. A stable dimeric structure is critical, as no catalysis is observ for mononuclear Mn. Scheme 2 represents the most likely mechanism for the catalase activity of the water oxidizing complex. 

The chloro dimer (1) has also been employed in Pd-catalyzed asymmetric hydrosilation of alkenes (eq 13). ... 

Figure 8-1 Geometrical structures for some Cu(II) earboxylate, hydroxo and chloro dimers.

Because the S = 1 spin states are thermally accessible, these dimers exhibit antifeiro-magnetic behaviour. For some of the Cu(II)-hydroxo and chloro dimers of Section 8-2, the groimd-states have S = 1 spin-states, and excited S = 0 spin-states are thermally accessible. When this occurs, the complex is ferromagnetic. 

Oxidative cleavage of the complex 549 with CuCri affords 2,3-bis(chloro-methyl)-1,3-butadiene (550) and regenerates PdCri. Thus the preparation of this interesting dimerization product 550 can be carried out with a catalytic amount of PdCl2 and two equivalents of CuCb in MeCN[495], Similarly, treatment of allene with PdBr2 affords the dimeric complex 551. Treatment of this complex with 2 equiv, of bromine yields the dibromide 552. The tetra-bromide 553 is obtained by the reaction of an excess of bromine[496]. Similarly,... 

Carbonylation of the complex 548 proceeds in ethanol gives ethyl 3-chloro-3-butenoate (554), The lactone 555 and the two esters 556 and 557 are obtained by carbonylation of the dimeric complex 549. The oxidative carbonylation of allene in ethanol with PdCl2 gives ethyl itacoante (558), although the yield is low[498]. 

Formic acid behaves differently. The expected octadienyl formate is not formed. The reaction of butadiene carried out in formic acid and triethylamine affords 1,7-octadiene (41) as the major product and 1,6-octadiene as a minor product[41-43], Formic acid is a hydride source. It is known that the Pd hydride formed from palladium formate attacks the substituted side of tt-allylpalladium to form the terminal alkene[44] (see Section 2.8). The reductive dimerization of isoprene in formic acid in the presence of Et3N using tri(i)-tolyl)phosphine at room temperature afforded a mixture of dimers in 87% yield, which contained 71% of the head-to-tail dimers 42a and 42b. The mixture was treated with concentrated HCl to give an easily separable chloro derivative 43. By this means, a- and d-citronellol (44 and 45) were pre-pared[45]. 

DPXC ndDPXD. The economic pressure to control dimer costs has had an important effect on what is in use today (ca 1997). Attaching substituents to the ring positions of a [2.2]paracyclophane does not proceed with isomeric exclusivity. Indeed, isomeric purity in the dimer is not an essential requirement for the obtaining of isomeric purity, eg, monosubstituted monomer, in the pyrolysis. Any mixture of the four possible heteronucleady disubstituted dichloro[2.2]paracyclophanes, will, after all, if pyrolyzed produce the same monomer molecule, chloro- -xyljIene [10366-09-3] (16) (Fig. 4). 

Except for the solvent process above, the cmde product obtained is a mixture of chloroprene, residual dichlorobutene, dimers, and minor by-products. Depending on the variant employed, this stream can be distiUed either before or after decantation of water to separate chloroprene from the higher boiling impurities. When the concentration of 1-chloro-1,3-butadiene [627-22-5] is in excess of that allowed for polymerisation, more efficient distillation is required siace the isomers differ by only about seven degrees ia boiling poiat. The latter step may be combiaed with repurifying monomer recovered from polymerisation. Reduced pressure is used for final purification of the monomer. All streams except final polymerisation-grade monomer are inhibited to prevent polymerisation. 

M2491). l-Chloro-3,4-dimethyl-2,5-bis(trimethylsilyl) arsole is reduced by calcium to give dimer 132. 

Reaction of 264 with l-chloro-4-phenoxybut-2-yne in the presence of K2CO3 gave 265. Oxidation of the latter with w-chloroperbenzoic acid gave the dimer 266. On the other hand, carrying the oxidation in presence of KCN afforded a mixture of 266 and 267 (87JCS(CC)524) (Scheme 47). 

On heating, the dichlorooxazolo[3,4- ]azepine 26, for which dimerization is prevented by the chloro groups, undergoes ring contraction and aromatization, involving a [l,2]-chlorine shift, to 5,8-dichloro-l,4-dihydro-2//-3,l-benzoxazin-2-one (27).11,153... 

The oxazolo[3,4-a]azepinones 4, in which 5 7 ring fusion imparts considerable planarity and hence antiaromatic character on the ring system, undergo spontaneous dimerization.153 The mode of dimerization appears to depend on the nature and position of substituents. The unsubstituted system and the 9-chloro derivative 4 (R1 = Cl R2 = H) produce the exo.anti-dimers, e.g. 5, upon spray-vacuum pyrolysis at 300 C, whereas the 7-/ert-butyl, 7-bromo, 7-methyl, and 7,9-dichloro (4, R1 = R2 = Cl) compounds yield the exo,syn-dimcrs, e.g. 6. 

Chloro-l//-l-benzazepines 2 are obtained as unstable red oils in excellent yields by heating 1 //-l-benzazepin-2(3//)-ones 1 with phosphoryl chloride in pyridine.208 Reaction conditions are important since in the absence of pyridine, or in dichloromethane solution, only poor yields of dimers, e.g. 3, are produced. The chlorobcnzazepines are stable for only short periods (24 hours in anhydrous pyridine) and rapidly polymerize. Isolation of the pure chloro compounds is difficult since they undergo very rapid hydrolysis to the benzazepinones. 

In general, the dimers have three chlorine bridges, and Ru3C18(PBu3)4 resembles the mixed-valence chloro complex Ru3Cl 2. A similar, but less extensively studied, pattern of behaviour has been found with other alkyl phosphines. 

A combination of 2-propyl ether in the first dimension with a chlorinated solvent mixture in the second was able to resolve both 3-chloro-5-sultone and the dimer sultone, which are not separated by the ether alone, plus all of the other sultones discussed. The sensitivity was increased by a factor of 2-4 because even with very large samples the spots are clearly resolved. When developed in one dimension, a very large sample gives a background streak and very faint spots cannot be seen. 

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