Nickel derivatives

There is spectroscopic evidence that the reduction of Ni(CO)4 gives rise to a large number of products, most of which have still to be isolated and characterized. Results obtained so far from a recent reinvestigation of this chemistry (95) suggest that all of the formulations previously reported in the literature are incorrect (76, 77, 116). 

Reduction under nitrogen of totracarbonyl nickel with alkali metals or sodium and lithium amalgams (71) in THF, or with alkali hydroxides in methanol, gives a mixture of the dianions [Ni5(CO) 42]2- and pMi6(CO) i2]2 (28, 95). The final composition of the reaction mixture greatly depends on the experimental conditions owing to the easily reversed equilibrium  

The yellow pentanuclear dianion, [Ni5(CO)i2]2-, is rather labile and has been isolated in a pure state only as the bis(triphenylphosphine)iminium salt by crystallization under carbon monoxide in anhydrous solvents. In wet solvents, it reacts readily with carbon monoxide to give a mixture of tetracarbonylnickel and an unstable hydride derivative presently formulated as [Ni(CO)3H] (t = 18.3), by comparison of its IR spectrum with those of [Ni(CO)3X] (X = Cl, Br, I) (31). This reaction contrasts with that of [Ni5(CO)i2]2 with water under nitrogen when the red dianion [Ni6(CO)i2]2- is formed. The reaction proceeds with formation of tetracarbonylnickel, hydrogen and traces of carbon monoxide and its stoichiometry is believed to be the following  

The mechanism should involve an easy initial protonation to give a hydride intermediate which then loses hydrogen and condenses to [Ni6(CO)12]2-. 

Equation (62) explains why precipitation from the original reaction mixture by addition of an aqueous solution of tetraalkylammonium salts always gives the red hexanuclear dianion [Ni6(CO)i2]2 (yields up to 60%). A comparison of its IR spectrum with that reported in the literature for [Ni4(CO)9]2 (76) strongly suggests that the latter should be re- 

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For the two metallocene systems, V(Cp)2 (d3), and Ni(Cp)2 (ds), the only acceptable assignments locate the 4> level between the two II levels in each case, and thus, using the data of Prins and Van Voorst (4 7), yield the parameters Ds = 3543 cm"1, Dt = 2074 cm"1 for the vanadium complex, and Ds = 3257 cm 1,Dt = 1806 cm-1 for the nickel derivative. Moreover, these authors, treating the available data for Fe(Cp)2, derived parameters corresponding to Ds = 5100 cm-1 and Dt = 2740 cm-1, from which it may be noted that, although the individual values of Ds and Dt vary appreciably from one complex to another, the ratio Dt/Ds remains approximately constant and shows the values 0.585,0.554,and 0.537 for the V, Ni, and Fe compounds respectively. More recently Sohn, Hendrickson, and Gray (48, 49) have successfully analysed the d-d spectra of several d6 systems in terms of parameters which lead to the ratios 0.525, 0.540, and 0.585 for Dt/Ds in the complexes Fe(Cp)2, Co(Cp)2+, and Ru(Cp)2 respectively, and it therefore seems reasonable to adopt an average value of 0.55 for this ratio for all metallocene systems. 

The hydrolysis of esters by the nickel derivative (271) provided an early example of the use of a metal-capped cyclodextrin as a catalyst (shown here as its p-nitrophenyl acetate inclusion complex) (Breslow Overman, 1970 Breslow, 1971). The synthesis of this host involves the following steps (i) covalent binding of the pyridine dicarboxylic acid moiety to cyclodextrin, (ii) coordination of Ni(n) to this species, and (iii)... 

By using combinations of hydrogenation and dehydrogenation reactions it has been possible to obtain nickel derivatives of the Curtis macrocycle containing from zero to four imine groups (Curtis, 1968 1974). Related reactions in the presence of a variety of other central metal ions have been described. The electrochemical oxidation of the Cu(ii) complex of the reduced Curtis ligand proceeds initially via a two-electron step to yield the monoimine complex (296) (Olson Vasilevskis, 1971). 

Diastereoisomeric transition states calculated for propene insertion in a model for a Brookhart-type Ni(II) catalyst, based on diacetylbis(2,6-diisopro-pylphenylimine)nickel derivative,143,144 are shown in Figure 1.21. Diastereomeric transition states for si (Figure 1.21a) and re (Figures 1.21b,c) monomer insertions into a si chain correspond to like (isotactic) and unlike (syndiotactic) propagations, respectively.144,143... 

Several nickel derivatives of the type [ANiXfi (A = allyl, X = halogen) are known, but they are very much less stable to air than the palladium compounds (76, 77). The small dipole-moment of bis (ally lnickel bromide) may mean that the nickel-bromine bridges are not coplanar (76). 

The allyl group itself may also be attached to a cyclopentadienyl-metal residue, giving compounds of the type (CjHsJMCCsHs). These are known for nickel (77, 152), palladium (232), and platinum (232a). The palladium and platinum compounds are remarkably stable the nickel derivative is. liquid at room temperature, and decomposes very readily in oxygen. 

Phase angles from experimental evidence. There is another set of circumstances in which the signs of the terms can be deduced from experimental evidence. This has been done for phthalooyanine itself. It so happens that the unit cell dimensions and space-group of the parent substance and the nickel derivative are identical, and it can be assumed that the orientations of the molecules are the same in both crystals. The centre of symmetry of the cell is occupied by hydrogen... 

The value of J is not known in the case of the copper-nickel derivative. However, the same line of discussion should hold for this derivative, whose spectrum is shown in Fig. 6.8B [29]. It is noteworthy that the R values of the protons of the copper domain are smaller in this case than in the cobalt case. This is probably due to a shorter electronic relaxation time of tetrahedral nickel(II) than tetrahedral cobalt(II) (see Section 3.3). In this respect it may be interesting to note that in the case of the cobalt-cobalt derivative we have a tetrahedral and a square pyramidal cobalt(II) ion [30,31]. The former has longer electronic relaxation times. Upon establishment of magnetic coupling, the electronic relaxation times of the tetrahedral cobalt(II) ion decrease and tend to reach the values of the square pyramidal cobalt(II) ion. This is evident by comparing the spectra of the protein containing only the tetrahedral cobalt(H) ion with those containing both ions (Fig. 6.9). 

Nitrosalicylaldehyde reagent test. This test is based upon the fact that 5-nitro-salicylaldehyde and nickel ions when added to a primary amine produce an immediate precipitate of the nickel derivative of the Schiffs base. 

Carbon disulphide reagent test. This test is based upon the formation from a secondary amine and carbon disulphide of a dialkyldithiocarbamate the latter readily forms a nickel derivative with a solution of a nickel salt ... 

The reaction of cinnamaldehyde with bis(cyclooctadiene)nickel is typical in benzene a bis(cinnamaldehyde)nickel derivative may be isolated in which the bonding is believed to be similar to that in bis(acrolein)nickel. 

When inhaled even in small quantities the vapour of nickel carbonyl is very poisonous,1 being decomposed in the lungs to carbon monoxide and a nickel derivative—possibly the basic carbonate. 

Dithiolene complexes, and more specifically the nickel derivatives, are involved in materials used for optical data storage, such as compact disc or laser disc read-only memory (CD- or LD-ROM), and also in copiers or photography related devices. In the latter case, it is the IR-absorbing property that is exploited. Some of these compounds can be found in reviews by Mueller-Westerhoff et al. (353, 354). Recent patents are given as examples in references (458—481). In the field of optical storage, short reviews were published in 1988 (482) and 1990 (362, 483). Here, the dithiolene complexes act as inhibitors of the laser-induced fading of the colored thin layers of the optical discs. They also act as an antioxidant and increase the photostability of the cyanine dyes that constitute the recording layer. Contrary to what was observed for the two... 

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