Nickel complexes properties

The electronic spectra and spectromagnetic properties of nickel complexes have been exhaustively described in CCC (1987)—in particular for Ni11. Hence, the present discussion will be restricted to selected examples of more recent work and emerging new methods. 

Quite a number of silylnickel and silylenenickel compounds have been reported, and only a few can be cited here2305-2309 Bis(silyl)nickel complexes have been implicated as important intermediates in Ni-catalyzed double silylation of various organic substrates. Using an o-bis(dimethylsilyl)carborane ligand, complex (930) could be isolated and structurally characterized 2310 Its unusual thermal stability is attributed to the advantageous steric and electronic properties of the carboranyl unit. (930) undergoes... 

Taylor Busch, 1967). In solution, these isomers are quite stable towards racemization - a property not normally characteristic of high-spin nickel complexes containing open-chain ligands. 

The eight-coordinate vanadium complex V(S2CMe)4 contains both dodecahedral and square prismatic eight-coordinate molecules in the same crystal.322 Of particular interest is the chain-like, mixed valence platinum complex [Pt2(S2CMe)4( i-I)]A, which displays unusual electrical properties metallic conduction between 300 and 340 K and semiconducting properties below 300 K,323 whereas the analogous nickel complex, [Ni2(S2CMe)4(p-I)]x is a semiconductor.324... 

Less clear is the sequence which leads to the formation of the active species in the case of catalysts prepared from zero-valent nickel complexes and aluminum halides or alkylaluminum halides (method C2). The catalytic properties of these systems, however—in particular, the influence of phosphines (76)—leaves no doubt that the active species is also of the HNiY type discussed above. In this connection, a recent electron spin resonance report that nickel(I) species are formed in the reaction of COD2Ni with AlBr3 (83 ), and the disproportionation of Ni(I) to Ni(II) and Ni(0) in the presence of Lewis acids (69) should be mentioned. 

This review is an attempt to rationalize the main reaction patterns observed so far in organonickel chemistry. Synthetic work in organic chemistry has found an exceedingly valuable tool in the use of nickel complexes. The reason for this lies in the fact that nickel possesses a very favorable combination of properties to meet the requirement for an organic reaction to take place via coordination. Let us consider, for example, which basic steps occur when organic ligands react on a transition metal to form C—C bonds. 

T. Yamamoto, A. Morita, Y. Miyazaki, T. Marayama, H. Wakayama, Z.H. Zhou, Y. Nakamura, T. Kanbara, S. Sasaki, and K. Kubota, Preparation of ir-conjugated poly(thiophene-2,5-diyl), poly(p-phenylene), and related polymers using zerovalent nickel complexes. Linear structure and properties of the TT-conjugated polymers, Macromolecules, 25 1214—1223, 1992. 

This isoindoline nickel complex pigment is mainly recommended for the coloration of metallics and effect coatings, especially for water based systems. P.R.271 affords yellowish to medium red shades, providing a bright flop in metallics. Alkyd/melamine resin systems may safely be overcoated and withstand exposure of 140°C for 30 minutes. The flow properties of P.R.271 in these systems and in polyester cellulose acetobutyrate base coat systems are good, but there is a certain tendency to flocculate. 

Several transition metal ions form stable complexes with aliphatic 1,2-dithiols, which absorb in the near-lR. Known as dithiolenes, their nickel complexes in particular have been found to have valuable properties. The physical properties of dithiolenes can be readily tailored by variations on the substituents attached to the dithiols, see (4.13). Although they have low molar absorption coefQcients, when compared to cyanines etc., they do have one big advantage in that they show very little absorption in the visible region." Stracturally analogous dyes can be made from aromatic dithiols and oxothiols (4.14), and the much more bathochromic naphthalene derivatives (4.15), but they are much weaker absorbers. 

Le Narvor N, Robertson N, Weyland T, Kilbum JD, Underhill AE, Webster M, Svenstrup N, Becher J (1996) Synthesis, structure and properties of nickel complexes of 4,5-tetrathia-fulvalene dithiolates high conductivity in neutral dithiolate complexes. Chem Commun 1363-1364... 

Fujiwara E, Kobayashi A, Kobayashi H (2003) Structures and physical properties of nickel complexes with TTF-type ligands. Synth Met 135-136 535-536... 

The thermal properties of the nickel complexes obtained with the cupferron ligand (260), NiLj, and with dicupferron (261), NiL-H20, were investigated.1916 1917... 

Standard enthalpies of formation of bis(dithiocarbamato)nickel(II) complexes were also reported2019 and the results indicate that Ni—O and Ni—S bond energies in square planar nickel complexes are approximately the same from a thermochemical point of view. The electron-transfer properties of various dithiocarbamato and diselenocarbamato complexes were investigated by voltammetric techniques.2020,2021 The observed processes were found to be irreversible. 

The chemistry of bis(l,2-dithiolene) complexes of nickel has stimulated considerable investigations over the past 20 years, owing to the peculiar and unusual electronic and electrochemical properties which the complexes exhibit both in the solid state and in solution. A number of articles cover the early reports up to 19701923 1925 1927 2108 on nickel complexes having general formulas (287) and (288). The formulas of representative complexes together with die synthetic routes and some physicochemical properties are summarized in Table 91. 

Unlike the tertiary phosphine and arsine oxides which form a variety of nickel complexes with peculiar properties, tertiary arsine sulfides and, particularly, tertiary phosphine sulfides... 

Nickel(H) complexes with ligands containing mixed donor atoms, in general N, O and S, are innumerable. In die present section we will mention complexes which are the archetypes or are suitable for the description of the properties of all complexes of the same type. Nickel complexes with hybrid polydentate ligands containing either P or As have been discussed in Section 50.5.4. 

Many types of ligand have been designed or are known to favour the formation of di- and tri-nuclear nickel complexes. This field of coordination chemistry has recently been extensively reviewed.2590,2591 For a specific discussion of the magnetic properties of dinuclear nickel(II) complexes, see Section 50.5.10. 

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