Nickel alkane complexes

The kinetics of the oxidative addition of nitriles to Ni(P—P)2 have been studied. The organocyano nickel(II) complexes presumably have a dinuclear structure with trans planar coordination for the nickel atom.270 Some of the [Ni(CN)(R)(PR3)2] compounds (R = alkyl, aryl) are unstable and therefore cannot be isolated in the solid state. Their decomposition in solution promotes the formation of alkanes, alkenes, diphenyl, etc.217... 

Busch et al. on their search for a cytochrome P450 model useful for the selective oxidation of alkanes investigated the macrobicyclic nickel(II) complex 71 with respect to its inclusion capacity for aliphatic alcohols and phenols. A shift of the host protons in the course of the guest addition (e.g. 1-butanol, phenol) in D O the formation of in-... 

For the aerobic epoxidation of 1,2-disubstituted olefins, the use of smaller amount of nickel(II) complex was effective to improve yield of the corresponding epoxide (B) Dilution Method). Isovaleraldehyde was found to be remarkably effective for the epoxidation of terminal olefin, and 1,2-epoxy alkane was obtained in good to high yield (C) Isovaleraldehyde Method). 

Another common example is a nickel-boron complex (Ni2B), which is often called the P-2 catalyst. A poisoned catalyst will catalyze the conversion of an alkyne into a cis alkene, but it will not catalyze the subsequent reduction to form the alkane (Figure 10.4). Therefore, a poisoned catalyst can be used to convert an alkyne into a cis alkene. 

Steric constraints dictate that reactions of organohalides catalysed by square planar nickel complexes cannot involve a cw-dialkyl or diaryl Ni(iii) intermediate. The mechanistic aspects of these reactions have been studied using a macrocyclic tetraaza-ligand [209] while quantitative studies on primary alkyl halides used Ni(n)(salen) as catalyst source [210]. One-electron reduction affords Ni(l)(salen) which is involved in the catalytic cycle. Nickel(l) interacts with alkyl halides by an outer sphere single electron transfer process to give alkyl radicals and Ni(ii). The radicals take part in bimolecular reactions of dimerization and disproportionation, react with added species or react with Ni(t) to form the alkylnickel(n)(salen). Alkanes are also fonned by protolysis of the alkylNi(ii). 

One type of chemical approach to the analysis of liquid and solid hydrocarbons that will probably see considerable development is that involving reaction or complex formation to yield precipitates that can be separated from the unreacted mass and subsequently be treated to regenerate the hydrocarbons or class of hydrocarbons so precipitated. This field is certainly not extensively developed. In fact very few examples come to mind but among these are Gair s (21) determination of naphthalene by precipitation with picric acid determination of benzene by Pritzker and Jungkunz (52) by an aqueous solution of specially prepared nickel ammonium cyanide Bond s (8) nitrous acid method for styrene and more recently the determination of normal alkanes in hydrocarbons of more than 15 carbon atoms by adduct formation with urea as described by Zimmerschied et al. (71). 

Early attempts at an asymmetric hydroalumination utilized a chiral sec-butylsal-icylideneimine (sec-busal) complexed to Ni(II). Thus, treatment of racemic 3,7-dimethyl-1-octene (1) with 0.2 mol % of the complex 2 and 0.3 equivalents of triisobutylaluminum at 0 °C followed by hydrolysis gave the alkane 3 in 1.2% ee as judged by optical rotation, Eq. (1). The unreacted olefin was recovered and found to have an ee of 1.8% on the basis of its optical rotation. The authors conclude that racemic product and starting material would be expected if a naked nickel lacking the ligand or colloidal nickel is involved [17]. 

In the calculations of methane interaction with nickel or titanium surfaces, five different modes of coordination have been considered (Figure III.2) [6c], It has been concluded that acts of methane activation by a separate molecule of a metal complex on the one hand and the metal surface on the another hand are very similar. In both processes the C-H bonds of methane are ruptured and new M-H bonds are formed. Intermediate species formed during alkane chemisorption on oxide catalysts have been investigated both by MO calculations and spectroscopic methods [7]. 

Nickel is an analogue of platinum and its oxidation state at which methane is produced is Ni(II) with a d electronic configuration, that is the same as that of Pt(II) which activates methane and other alkanes (see Chapter VII). Evidently the activation of methane on platinum complexes may be considered a conditional model for biological anaerobic oxidation of alkanes. It is of importance that Ni(II) as well as Pt(II) is a so-called soft acid and could prefer to react with methane ( soft base) rather than with such strong hard base as water, therefore surrounding water does not prevent this reaction. 

H bond of alcohols such as phenols or fluorinated alcohols is cleaved by dialkylmetal(II) complexes to give (alkyl)(aryloxo)- or (alkyl)(alkoxo)nickel(II) and palladium(II) complexes with evolution of alkane (Eq. 3.55) [190], Some aryloxo and alkoxometal complexes have enough basicity to have strong hydrogen bonding with free alcohol both in solid state and in solution. 

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