Derivatives of Palladium

So far, palladacyclopentane complexes, unlike the nickel and platinum analogs, have been relatively little explored, one of the reasons probably being the lack of general synthetic routes. 

Described here is the synthesis of some palladacyclopentanes starting from easily accessible salts of palladium(ll) with nitrogen and phosphorus ligands. 

PdCl2(diphos) + LiCH2(CH2)2CH2Li------ PldCH2(CH2)2CH2(diphos) + 2LiCl 

Dichloro[l,2-ethanediylbis(diphenylphosphine)]palladium(II) is prepared according to the literature1 by adding to K2PdCl4 (2 g, 6.127 mmole) in anhydrous V,V-dimethylformamide (20 mL) a solution of l,2-ethanediylbis(di-phenylphosphine) (diphos) (2.44 g, 6.127 mmole) in dichloromethane (12 mL). The resulting yellow suspension is refluxed for 2 hr, under stirring. Upon cooling and dilution with water, a white solid forms which is separated from the solution, washed with diethyl ether, and dried under vacuum. The yield is 3.34 g (96%), mp 326°. 

All the following reactions and operations should be carried out under argon, and all solvents must be saturated with argon before use. 

Submitted by P. DIVERSI, G. INGROSSO, and A. LUCHERINI Checked by K. A. ERNERt and T. H. TULlPt 

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All three metals of this group give rise to ammino-derivatives the compositions of which, however, differ considerably. The ammino-derivatives of ruthenium mostly contain a nitroso-group as well as ammonia the ammino-derivatives of rhodium salts closely resemble the cobalt -ammines and the ammino-derivatives of palladium salts correspond to the ammino-derivatives of platinum salts. 

Ammonia combines with palladium salts, yielding ammino-com-pounds. These are, however, mostly derivatives of the stable palladous salts. Thus the two principal groups of the ammino-derivatives of palladium are the pallados-ammines or diammino-palladium compounds, 1 Jorgensen, J. prald. Ohem., 1886, 34, 396. 2 Jorgensen, ibid., 1883, 27, 478. 

The first ammino-derivative of palladium was prepared by Vauquclin in 1813.1 Vauquelin s salt, the chloropalladite of tetranunino-palladium, [Pd(NH3)4]PdCl1, corresponds to the green salt of Magnus, the first known compound of the ammino-platinum salts. 

The ammino-derivatives of palladium have been investigated principally by Fischer, Fehling, and Miiller.2... 

An optically active derivative of palladium has been prepared by combining potassium chloropalladite with 1-propylenediamine. This salt has a rotation [a]o-f-79-25°, [M]d+258-1°. It is analogous to the corresponding platinum compound, but the rotation is much greater, thus showing the influence of the central metallic atom in increasing or diminishing the rotation.2... 

In these the metal is divalent, tetravalent, and trivalent respectively. The ammino-iridous and the ammino-iridic salts correspond to the ammino-derivatives of palladium and platinum, whilst those of the sesqui-salts are analogous to the ammino-derivatives of cobalt, chromium, and rhodium. 

Ammino-derivatives of Ruthenium Halides—Derivatives of Ruthenium Salts containing a Nitroso-group—Ammino-derivatives of Rhodium Salts— Ammino-derivatives of Palladium Salts. 

Alkali hexachlorosmates are isomorphous with the corresponding derivatives of palladium, iridium, and platinum, and may therefore be assumed, by application of the Law of Mitscherlieh, to have the general formula M20sC16. 

Fluoride derivatives of palladium(II) and platinum(II), all of which are phosphine derivatives, can be most simply grouped into one of two subsections, namely neutral or cationic species. The neutral species are all of the form [MXF(PPh3)2] (M = Pd, Pt) where X can be Cl, Br, I, H, methyl, phenyl and C6F5. The synthetic route into these compunds involves either addition of HF to a metal phosphine dihalide or... 

Chemical shifts have been reported for [Me3CCH2HgX] 203) (see Table XII), tr-allylic derivatives (see Table XIII), o-cyclopentadienyl derivatives (see Table XIV), and miscellaneous compounds (see Table XV). In the case of fluxional a-cyclopentadienyl derivatives, it has been shown that chemical shifts can be used to differentiate between fluxional o-cyclopentadienyl derivatives and w-cyclopentadienyl derivatives 103). The NMR spectrum of [Sb(cyclopropyl)s] has only two carbon resonances, showing that the molecule is fluxional (56) and the NMR spectrum of the naturally occurring organometallic compound, 5 -deoxyadenosylcobalamin, has been reported (65). For a number of norbornane and allylic derivatives of palladium and platinum, a number of linear relationships have been found between chemical shifts of various carbon atoms. It was suggested that a term due to paramagnetic shielding by the metal was dominant 52b). 

Studies on carbonyl derivatives of palladium(II), plat-inum(II), silver(l), and gold(l) have established the following points ... 

Another example of tr-allyl ligand transfer has been described recently by Heck 159). Treatment of tr-allyl derivatives of palladium chloride with NaCo(CO)4 in ether gives tr-allyl cobalt complexes. 

Methyl and phenyl derivatives of palladium(II) were reported " to undergo carbon monoxide insertion readily at ambient conditions [reaction (h)], whereas the corresponding platinum(II) derivatives were carbonylated under more drastic conditions (90°C and 50-100 atm), consistent with the comparative kinetic data. 

Pyridine-2-carboxylato (pyca) derivatives of palladium(II) have been found to undergo carbon monoxide insertion into the palladium-methyl bond ... 

Alkanes can be oxidized in the presence of some transition metal complexes in aqueous and acidic media For example, in concentrated sulfuric acid the oxidative properties of the complexes are enhanced. Solutions of derivatives of palladium(II), platinum(III), manganese(III) and mercury(II) as well as some other compounds (hydrogen peroxide, ammonium persulfate, nitric acid and even concentrated sulfuric acid itself) can be used as oxidants. In the cases of metal-free oxidants the active species are apparently electrophiles such as NO2 or SO3I-C (for nitration of aromatics, see, for example, recent publication [40] and references therein). 

A corresponding colorless crystalline derivative of palladium(II), 7r-l,5-CgHi2PdMe2, is obtained from 7r-CgHi2PdCl2 and methyllithium at - 40° C, but is very much less stable than its platinum analog 22). 

A TT-allyl derivative of palladium(II) chloride is first formed, to which carbon monoxide can be added (Fig. 7-15 ). Similarly, an olefin is converted to the acid chloride in the presence of palladium metal, hydrochloric acid, and carbon monoxide (Fig. 7-15. ). 

The first type of process can be catalyzed by derivatives of palladium, nickel and cobalt, according to basically the same scheme of the catalytic cycle, involving oxidative addition of the reduced form of the metal catalyst across the R-X bond, insertion of CO to form a a-acyl complex, which is then cleaved by the nucleophile to form the final product and regenerate the catalyst. Alternatively, the nucleophile may attack the carbonyl ligand with subsequent reductive elimination. This mechanism is also reasonably... 

General Considerations. Many of the reactions described below can be accomplished using derivatives of palladium chloride such as potassium tetrachloropaUadate(II), disodium tetra-chloropalladate(II), Bis(benzonitrile)dichloropalladium(II), dichlorobis(acetonitrile)palladium, and dichloro-... 

Synthesis and characterisation of C-bonded (1,5-cod)alkoxo derivatives of palladium(II) and platinum(II). 

In general, the chemistry of pincer derivatives of palladium and platinum is very closely related, affording in many cases analogous species and reactivity. Thus, for the sake of discussion, the chemistry ofboth metals is included in this section and we will be switching from one metal to another unless a specific reaction or product refers to one metal solely. 

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