Nickel-carbonyl complex, tetrahedral

Reactions of the tetrahedral Ni° complex (994) have already been discussed in Section 6.3.5.4.2397 A nickel carbonyl cation (1062) containing a cyclophosphenium ligand has been assembled through a hydride abstraction reaction according to Equation (37).2552... 

In summary, it can be seen that the structural chemistry of the zero-valent complexes has to date been dominated by investigations on nickel carbonyl. Preliminary studies on other compounds indicate that the tetrahedral structure may not be the only possibility, and thorough investigation of the unsaturatcd species is likely to develop. Back-donation may be examined by study of force constants, in favorable cases merely of observed frequencies, and it would be interesting to see more cases of competition for back-donation, as in (MeNC)3Ni(CO). 

Griffith el al. (Ill, 112) have shown that the blue compounds obtained by the interaction of nitric oxide and nickel carbonyl in the presence of water or an alcohol (68) have the general formula Ni(NO)(OR)3, and are probably tetrahedral. The N—0 stretching frequency of 1828 cm-1 in Ni(NO)(OH)3 indicates coordination of N0+ the spectra show absorption at 15,500 cm-1, in agreement with other such complexes, but the magnetic moment of Ni(NO)(OH)3 is only 2.97 B.M., which indicates considerable distortion. 

There have been several ab imto LCAO MO SCF calculations on tetrahedral transition-metal complexes for example, see the work of Hillier and Saunders (Molecular physics 22, 1025 (1970)), and Demuynck and Veillard (Theoretica chimica acta 28, 241 (1973)) on nickel carbonyl Ni(OO). ... 

Phosphorus trioxide forms various addition complexes using its lone pair electrons to complete a tetrahedral configuration (Figure 4.10). With diborane it forms P4O6 nBHj, and with nickel carbonyl it forms P40g nNi(C0)4, where n = 1-4 (Chapter 10). Phosphorus is obtained on heating phosphorus trioxide with arsenic or antimony in a sealed tube (4.75). Recent work [8] has shown that the trioxide also reacts with ozone at low temperatures to form an ozonide of composition P40,g (4.66c). Another substitution in the cage molecule is (4.76) [9]. 

Another valuable transition metal, nickel, is purified by a process first formulated by Ludwig Mond in the 1890s. In the Mondprocess, the impure nickel metal is subjected to a warm (approximately 75°C) stream of carbon monoxide gas. The gaseous, tetrahedral tetracarbonylnickel(O), Ni(CO)4 (often commonly called nickel tetracarbonyl), is immediately formed and allowed to pass into another chamber at about 225°C. (Other transition metals present as impurities are not similarly complexed.) At the higher temperature, the equilibrium between soHd nickel, carbon monoxide, and the nickel carbonyl [as shown in Equation (6.7)] is reversed, and pure nickel is deposited. 

The pale yellow [Ni(PEt3)4] is also tetrahedral but with some distortion. In sharp contrast to nickel, palladium forms no simple carbonyl, Pt(CO)4 is prepared only by matrix isolation at very low temperatures and reports of K4[M(CN)4] (M = Pd, Pt) may well refer to hydrido complexes in any event they are very unstable. The chemistry of these two metals in the zero oxidation state is in fact essentially that of their phosphine and arsine complexes and was initiated by L. Malatesta and his school in the 1950s. Compounds of the type [M(PR3)4], of which [Pt(PPh3)4] has been most thoroughly studied, are in general yellow, air-stable solids or liquids obtained by reducing complexes in H2O or H20/EtOH solutions with hydrazine or sodium borohydride. They are tetrahedral molecules whose most important property is their readiness to dissociate in solution to form... 

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