Nickel sulfur derivatives

Thiocarbonyl derivatives of 1,3-dioxolanes and 1,3-oxathiolanes are readily isomerized to the 2-carbonyl compounds as shown in Scheme 20. Alkylation of the sulfur atom with alkyl halides usually leads to ring-opened products (Scheme 21) (69JOC3011). Most of the other chemistry of the sulfur derivatives has focused on desulfurization and subsequent generation of alkenes. The reaction is shown in equation (20) and proceeds with cis elimination via carbene intermediate (see Section 4.30.2.2.5) and is usually carried out with a phosphine (73JA7161) or a zero-valent nickel complex (73TL2667). 

In principle, the SBA/Topspe process consists in mixing the burner exit gases with steam and sending the mixture to a fixed-bed reactor on a nickel base catalyst, at about 2.10 Pa absolute and about 950 C This technique, sometimes called partial catalytic oxidatioEu is only applied to the conversion of natural gas, LPG and naphthas, particularly because, if heavier feeds are used, problems arise in the prior separation of sulfur derivatives that cannot be t[Pg.42]

Active Raney nickel induces desulfurization of many sulfur-containing heterocycles thiazoles are fairly labile toward this ring cleavage agent. The reaction occurs apparently by two competing mechanisms (481) in the first, favored by alkaline conditions, ring fission occurs before desul-, furization, whereas in the second, favored by the use of neutral catalyst, the initial desulfurization is followed by fission of a C-N bond and formation of carbonyl derivatives by hydrolysis (Scheme 95). 

Another use of 4-/ f2 octylphenol is ia the productioa of uv stabilizers. 4-/ f2 -Octylpheaol reacts with sulfur dichloride to yield the thio-hisphenol derivative, which thea reacts with nickel acetate to form 2,2 -thiobis(4-/ f2 octylphenolate)-A/-butylamiQe nickel [14516-71 -3]. This type of stabilizer is widely used in the production of outdoor carpeting based on polypropylene fibers. Nickel compounds give a green discoloration which limits their apphcatioas. A second class of uv stabilizers based on the benzotriazole stmcture. 2-(2 -hydroxy-5 -/ f2 octylphenyl)benzotriazole [3147-75-9] is produced from 4-/ i -octylphenol (55). 

This paper surveys the field of methanation from fundamentals through commercial application. Thermodynamic data are used to predict the effects of temperature, pressure, number of equilibrium reaction stages, and feed composition on methane yield. Mechanisms and proposed kinetic equations are reviewed. These equations cannot prove any one mechanism however, they give insight on relative catalyst activity and rate-controlling steps. Derivation of kinetic equations from the temperature profile in an adiabatic flow system is illustrated. Various catalysts and their preparation are discussed. Nickel seems best nickel catalysts apparently have active sites with AF 3 kcal which accounts for observed poisoning by sulfur and steam. Carbon laydown is thermodynamically possible in a methanator, but it can be avoided kinetically by proper catalyst selection. Proposed commercial methanation systems are reviewed. 

Table 5 shows HDS product distributions over several catalysts prepared by using the molybdenum-nickel cluster 2. Sulfur content in decane was adjusted to 5.0 wt% in these experiments. MoNi/NaY was found to be more active than MoNi/Al203. It is to be noted that during the high temperature pretreatment the original cluster structure would have been changed. However, the high activity of the MoNi/NaY catalyst for benzothiophene HDS is probably due to the formation of active sites derived from this particular mixed metal cluster. 

A range of L-cysteine derivatives bearing a 1,2,4-triazolyl residue on the sulfur atom has been prepared by the asymmetric Michael addition of 4,5-dialkyl-3-mercapto-l,2,4-triazoles to a nickel Schiff base complex. The enantiomeric excesses of the product aminoacids were measured and found to be greater than 98.5% in some cases <2004TA705, 2004RCB932, 2004IZV894>. 

Synthesis. These macrocycles are prepared from seven-membered ring dinitrile complexes, 84a-84c (Scheme 17), which contain either methylene, sulfur or oxygen in the five position (129). These cyclic dinitriles are synthesized by alkylating maleonitrile dithiolate or derivatives thereof with the corresponding dihalide. The dinitriles 84a-84c can be cyclized in magnesium propoxide to form porphyrazines 85a (33%), 85b (19%), and 85c (27%) (Scheme 17), which can be demetalated with trifluoroacetic to form 86a-86c. Additionally, 86a has been remetalated with nickel (87a, 92%), copper (88a, 95%), and zinc (89a, 94%). The sulfur and oxygen derivatives 85b, 85c, 86b, and 86c are of low solubility and are not suitable for further manipulation. 

In practice the sulfur-containing derivative is dissolved or suspended in a suitable solvent, treated with a sufficient quantity of Raney nickel, and either left at room temperature or heated under reflux, recovery of the product being effected by concentration of the liquid phase. The following example may be taken as typical.7... 

In addition to hydrocarbons, petroleum also contains compounds that consist of nitrogen, oxygen, and sulfur (in the minority) as well as trace amounts of metals such as vanadium, nickel, iron, and copper. Porphyrins, the major organometaUic compounds present in petroleum, are large, complex cyclic carbon structures derived from chlorophyll and characterized by the ability to contain a central metal atom (trace metals are commonly found within these compounds). 

The Gassman indole synthesis involves a one-pot process in which a hypohalite, a P-carbonyl sulfide derivative, and a base are added sequentially to an aniline or a substituted aniline to provide 3-thioalkoxyindoles. The sulfur can be easily removed by hydrogenolysis or Raney nickel. 

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