Mono crystals palladium

As described in the previous section. Ni(cod>2 is used as a versatile precursor to organonickel complexes (see Section 12.2). On the other hand, the corresponding palladium complex Pd(cod)2 is too unstable to be handled [77]. Therefore, the more stable palladium(O) olefin complex Pd Cdba) (dba = dibenzylideneacetone) is generally employed instead (eq (56)) [78]. The dba complex can be isolated as air-stable purple crystals and stored at room temperature without decomposition. This complex was applied to the synthesis of various palladium(O) olefin complexes [79] and mono-organopalladium(II) complexes. 

In the meantime, Ohta et studied the complete series of symmetric copper complexes ((53) M = Cu R = R = C H2 +i, = 0 to 14), which confirmed the previous results. The ligand showed a crystal smectic E phase from the octyl derivative onwards as determined by miscibility studies. The first four complexes ((53) M = Cu R = R = C H2 +i, = 0 to 3) were not mesomorphic, then a mono tropic phase was detected for = 4, which became enantiotropic for > 5. Moreover, for n = l and 8, the copper complexes showed an additional mesophase, while the nonyl derivative exhibited two additional mesophases. Crystalline structures of some tetra-alkyl copper, palladium, and nickel complexes of / -diketonates revealed that the flat molecular species were stacked into columns, the planes of the molecules forming a small tilt with respect to the columnar axis-these columns were further organized into layers. Variable-temperature and NMR ... 

Selectivity is a major issue for the mono-chlorination of acetic acid to chloroacetic acid since second chlorination gives dichloroacetic acid and other chlorinated species including add chloride formation [132]. The removal of these impurities, especially of the dichloroacetic add is laborious and costly, either by crystallization or by reduction with a palladium catalyst. 

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