Chloro palladation

Butyrolactones are prepared by intramolecular reaction of haloallylic 2-alkynoates. The a-chloromethylenebutyrolactone 301 is prepared by the intramolecular reaction of300[150,151]. 4 -Hydroxy-2 -alkenyl 2-alkynoates can be used instead of haloallylic 2-alkynoates, and in this reaction, Pd(II) is regenerated by elimination of the hydroxy group[152]. As a related reaction, the q-(chloromethylene)-7-butyrolactone 304 is obtained from the cinnamyl 2-alkynoate 302 in the presence of LiCl and CuCbflSS]. Isohinokinin (305) has been synthesized by this reaction[l 54]. The reaction is explained by chloro-palladation of the triple bond, followed by intramolecular alkene insertion to generate the alkylpalladium chloride 303. Then PdCb is regenerated by attack of CuCb on the alkylpalladium bond as a key step in the catalytic reaction. 

Tetrammino-palladous Chloro-palladate, [Pd(NH3)4]PdCl3, is produced by the action of chlorine on cold aqueous diehloro-diammino-palladium, or by the action of aqua-regia on tetrammino-palladous chloride. The substance is a brownish-black crystalline body. It is precipitated and decomposed by hydrochloric acid, with liberation of nitrogen, the formation of ammonium chloride and porous palladium. Boiling water decomposes it into ammonium chloro-palladite. The corresponding bromo-palladite, [Pd(NH3)4]PdBr4, and nitrito-palladite, [Pd(NH3)4]Pd(N02)4, are also known. ... 

Dipyridino-palladic Chloride, [Pd py2]Cl4, is formed by the action of chlorine on dichloro-dipyridino-palladium suspended in chloroform. It crystallises in small orange-coloured prisms, and rapidly loses chlorine on exposure to moist air. If heated with potassium hydroxide a brown precipitate of palladic hydroxide separates, and if this is carefully neutralised with hydrochloric acid, potassium chloro-palladate crystallises out. Treatment with an aqueous solution of potassium iodide decomposes the salt, with formation of the palladous compound thus ... 

An interesting feature brought out by kinetic studies of chloride exchange is that cis addition does not occur unless chloride is available to fill the incipient coordination site. This shows itself as a [LiCl] term in the numerator of the rate expression. The scheme for cis chloro-palladation is shown in Equation 18. 

The principal compounds of palladium are the salts of chloro-palladous acid, H2PdCl4, and chlorc alladic acid, HgPdClg. The chloropalladite ion, PdCl —, is a planar ion, consisting of the palladium atom with four coplaiiar chlorine atoms arranged about it at... 

The catalyst is previously prepared in an apparatus for catalytic hydrogenation, in which are placed 0.5 g. of palladous chloride, 3.0 g. of Norite, and 20 ml. of distilled water. The bottle is swept out with hydrogen and then shaken with hydrogen for 2-3 hours at 2-3 atmospheres (40 lb.) pressure. The palladium on carbon is collected on a Biichner funnel, washed with five 50-ml. portions of distilled water, then with five 50-ml. portions of 95% ethanol, and finally twice with ether. Upon drying, about 3 g. of the catalyst is obtained. It is stored in a vacuum desiccator over solid sodium hydroxide. If the reduction of the chloro-lepidine does not proceed normally, the used catalyst should be removed by suction filtration and a fresh 3-g. portion of catalyst added. Failure of the reduction step is usually due to an inactive catalyst or to impurities in the acetic acid or chlorolepidine. The palladium catalysts, prepared as described elsewhere in this volume, are presumably also satisfactory for the reduction of 2-chlorolepidine (p. 77). 

Palladous salts on treatment with excess of ammonia yield tetram-mino-palladous salts, from which on the addition of acid the corresponding diacido-diammino-compounds are precipitated. This method may be employed for the preparation of the chloro-, bromo-, and iodo-compounds, which are sparingly soluble in water, and the other members of the series are prepared from these by double decomposition. Ammonia transforms the compounds info tetrammino-palladous salts. 

The nitrato-derivative of the series is unknown. Treatment of palladous nitrate with ammonia does not yield the corresponding nitrato-derivative, which appears to be unstable. A liquid is, however, obtained by treating the chloro-derivative with silver nitrate, but on evaporation a brown substance separates which detonates on heating. 

Kotsinaris et al. 1998), while on Ag and Pt cathodes methane was the main product. Rondinini et al. (2004) observed the preferential formation of methane from poly-chloromethane on silver in ACN, DMF and aquo-organic solvents. Trichloroethene and trichloromethane were hydrodehalogenated in aqueous solution at different pHs by Chen et al. (2003) on platinized and palladized ceramic (ebonex) supports. Main reaction products were ethane, ethene and HC1 for the former substrate, and methane and HC1 for the latter. In a preceding study (Chen et al. 1999) in oxidative conditions, they observed the parallel degradation to carbon-containing products (mainly CO2) and, in neutral or alkaline pH, Cr/CI()3 as the only chloro-containing products. 

Chiral phosphines are readily available from lithiated or palladated tertiary ferrocenylalkyl amines by reaction with chlorodiarylphosphine or chlorodialkyl-phosphine. As the chemistry of such phosphines is the topic of a separate chapter of this book (see Chapter 2), we will mention just a few aspects here. As with the phosphines, the corresponding derivatives of arsenic are obtained from chloro-diarylarsines [139],... 

Treatment of the thioxo compound 73 with Raney nickel readily results in desulfurization to give 2-methylpyrido[3,4-f)]pyrazine. Hydrogenation of the chloro compound 76 over palladized calcium carbonate gives the parent heterocycle. In contrast to the ease of reduction of 1,2,3,4-tetrahydro-2,3-dioxopyrido[2,3-h]pyrazine, its pyrido[3,4-b] analogue... 

Enantiotropic SmA mesophases were obtained in mixed heteropolynuclear complexes containing enaminoketone and or7, ti-palladated imine groups 28 transition temperatures and temperature ranges depended strongly on the nature of the enaminoketone derivative. The trinuclear bis(imine) and the tetranuclear chloro-bridged precursory complexes were also mesomorphic, showing an unidentified smectic phase (Cr 118 S 131 I) and a SmA phase (Cr 238 SmA 248 I) respectively. 

Similarly, smectic mesophases were obtained in heteronuclear or/ o-palladated imine complexes based on various non-mesomorphic enaminoketone ligands ((263) to (265), Figure 104). The precursor chloro-bridged complex was also mesomorphic, showing an SmA phase between 238 and 248°C. ... 

As above (242), the dinuclear ort/ o-palladated complexes derived from (S)-2-(2-hydroxyaryl) oxazoline Schiflf-base ligands ((277) X = OAc, Cl x = 1 R = CHMez x = 1,2 R = C HCH3CH2CH3) showed a broad SmA phase. In the planar, chloro-bridged complexes (cis. trans mixture 1 2), the phase existed from 50 °C to 170 °C, and up to 250 °C for the biphenyl derivative as far as the non-planar acetato-bridged complexes (only tram isomer) were concerned, only the biphenyl derivative was mesomorphic (g 71 SmA 121 Cr 179 SmA 232 I). Used as chiral dopants (ca. lOmol.%), a chiral nematic phase was induced systematically in both the chloro- and acetato-ljridged series, with the suppression of the SmA phase in the chloro-bridged systems (x = 1). 

The stereochemical course of the cycloaddition depends on the presence of silver perchlorate or tetrafluoroborate in the reaction medium [155]. Therefore, it is possible to select either the exo- or the enifo-cycloaddition reaction pathways by controlling the number of coordination sites on the orf/io-palladated naphthylamine template, hi the ewifo-cycloaddition pathway, the kinetically stable chloro ligand is coordinated to the neutral template, but in the exo-cycloaddition pathway, the kinetically labile perchlorato ligand forms a cationic intermediate which... 

Heteroleptic heterodinuclear m-Pd (C N)2 complexes such as 56 are obtained from the reaction of or/i o-mercurated 2-[(77 -phenyl)tricarbonylchromium]pyridine with /x-chloro cyclopalladated aromatic compounds in the presence of large amounts of [NMe4]Cl. The products are valuable precursors of planar chiral cyclopalladated Gr( 7 -arene)(GO)3 complexes, for example, 57. A series of or// o-palladated binuclear Gr(r7 -arene)(GO)3... 

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