Nickel complexes hydrogen cyanide reactions

Hydrogen cyanide smoothly adds to butadiene (BD) in the presence of zero-valent nickel catalysts to give (3PN) and (2M3BN) [1,4- and 1,2-addition products, respectively, Eq. (7)]. A variety of Ni[P(OR)3]4 (R = alkyl or aryl) complexes are suitable as catalysts. The reaction may be carried out neat or in a variety of aromatic or nitrile solvents at temperatures from 50-120°C. Whereas in many olefin hydrocyanations it is desirable to keep the HCN concentration very low to protect the nickel from degradation, with butadiene HCN may be added batchwise as long as the HCN concentration is kept near the butadiene concentration. In the case of batch reactions one must be cautious because of possible temperature rises of 50°C or more over a period of a few minutes. Under typical batch conditions, when Ni[P(OEt)3]4, butadiene, and HCN are allowed to react in a ratio of 0.03 1.0 1.0 at 100°C for 8 hr, a 65% conversion to 3PN and 2M3BN (1.5 1) is observed (7). 

Addition of hydrogen cyanide to a terminal alkene is catalyzed principally by nickel and palladium complexes. The reaction may give either linear or branched products (equation 161). The reaction is of considerable industrial interest. A review on the earlier work is available.599... 

Complexes of 82 have also been formed by the reaction of 2,6-diacetylpyridine and Af.Af-hwQ-aminopropyOamine in the presence of nickel(II) chloride and copper(II) chloride50). Other metals that have been used include copper(II) 63,64), nickel64165), cobalt(II) 66), manganese(II)73>, cobalt(I)69), eobalt(III)68,70-72), zinc(II)73>, and ruthenium(II)74). Kam and Busch 51 have reported the catalytic hydrogenation of the nickel(II) perchlorate complex of 82 to afford two nickel(II) complexes of 83 a yellow minor component and a red major component which preliminary studies indicate to be the meso form (84). The isomeric ligands can be displaced from the respective reduced complexes by cyanide ion. Ligand 84 has also been isolated and characterized as the cobalt(III) 67), iron(II)61,62), iron(III) 62>, and copper(II) complex 75,76). Dehydro — 82 has also been synthesized and complexed with nickel(II) 65,65a), and nickel(III)65 a. ... 

Hydrocyanic acid is most easily prepared from its potassium salt, K(CN), which is obtained principally by the decomposition of the complex double cyanides of iron as we shall soon consider. The acid is also obtained by the hydrolysis of certain glucosides, e.g., amygdalin, in bitter almonds. It is prepared synthetically by reactions to be discussed presently in connection with the constitution of it and its salts. It is a colorless liquid with a characteristic odor and burns with a violet flame. It boils at 26.1 and solidifies to crystals which melt at —14°. It is an extremely strong poison the best antidotes being chlorine and hydrogen dioxide. It is readily absorbed by metallic nickel which is thus used in gas masks for this purpose. It is stable in dry air but in presence of water is readily hydrolyzed yielding ammonia and formic acid as the chief products. 

Nickel.— Phosphine and phosphite complexes of nickel(0) react with strong acids to produce complexes [NiHL4]+. Reaction with weak acids may proceed further, with attack of the anion at the nickel. Thus the complex Ni(LL)a, where LL = l,4-bis(diphenylphosphino)butane, reacts with hydrogen cyanide to form firstly a hydride, which reacts quickly with cyanide to give the bimolecular intermediate Ni2(CN)2(LL)a. The ultimate products are the nickel(n) monomer Ni(CN)2(LL)2 and dimer [Ni(CN)2-(LL)]2. Ni(PPh3)4 undergoes normal oxidative elimination reactions with aryl halides to produce the new nickel(n) complexes Ni(aryl)(X)-(PPh3)2. ... 

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

The reactions of CN with nickel(II) compounds of the C-racemic ligand, (8), have been followed kinetically. " The square-planar complex exists in three forms a, with hydrogens 1, 8 up and 4, 11 down with all hydrogens down and 7, with 4, 8 up and 1, 11 down. Transformation between the isomers is dependent on [OH j. All three isomers rapidly equilibrate with one CN" to form [Ni(tetraL)CN], and addition of the second CN is rate determining. Though the final product is [Ni(CN)4], trans addition of the second CN" produces an unreactive octahedral complex [Ni(tetraL)(CN)2]. The final product is believed to be produced via cis addition of the second cyanide, following a hydrogen-bond interaction with one of the NH units (Scheme 6). 

Ethylene reacts with carbon monoxide and water in the presence of nickel carbonyl to give propionic acid in high yield. If care is taken to maintain a high concentration of propionic acid in the reaction mixture and the temperature, which is normally 300 in the propionic acid synthesis, is decreased to 240 °C propionic acid anhydride is formed in high yield in the presence of Ni(CO)4. Propionic acid ethyl ester is the main product in the reaction of ethylene, carbon monoxide and water (low water concentration must be applied) with cobalt carbonyls instead of Ni(CO)4. The conversion of ethylene with carbon monoxide in dilute alkaline medium with the aid of potassium nickel cyanide gives propionyl propionic acid [403-405]. At higher temperatures and without pH correction in the same reaction mainly polyketones with the sequences -(CHg-CHg-CO)- are formed. If the reaction is carried out in absence of water or alcohols and in presence of palladium iodide as catalyst, a mixture of hexenolide isomers is the main product. Colorless polyketones of the same structure are obtained if an excess of ethylene is treated with carbon monoxide in the presence of complex palladium salts as catalysts in an alcoholic hydrogen halide solution at 100 °C and 700 atm [406]. 

---