Adiponitrile complexes

Cu(nitrile)2N03 Wc refer later to the adiponitrile complex ( = 4). 

PA-6,6 is made from the relatively expensive materials hexamethylene diamine and adipic acid. An alternative synthesis of PA-6,6 from adiponitrile and hexamethylene diamine utilizing water is under investigation.16 PA-6 can be synthesized in a continuous process at atmospheric pressure, but reaction times are very long as the ring-opening initiation step is particularly slow. The reaction time can be shortened considerably by carrying out prepolymerization in the presence of excess water at pressure however, this makes the continuous polymerization process more complex. Copolymers with amide units of uniform length (diamides) are relatively new the diamide units are able to crystallize easily and have a thermally stable crystalline structure. 

Hydrocyanation represents a reaction of considerable economic importance largely due to the value of the DuPont process involving HCN addition to butadiene to afford adiponitrile.61,62 The mechanism is well known, and involves (i) oxidative addition of H-CN to a coordinatively unsaturated metal complex, (ii) coordination of an alkene to the H-M-CN species, (iii) migratory... 

Rate data have appeared (161) for the hydrodimerization of acrylonitrile to adiponitrile, which is catalyzed by various ruthenium-phosphine complexes (/, p. 101). 

More recently, dihydrogen complexes have been patented for nitrile hydrogenation. For example, the complex Ru(7/2-H2)2(H)2(PCy3)2 (Fig. 3.6) catalyzes the hydrogenation of adiponitrile to hexamethylenediamine (HMD) in toluene at 90 °C, 70 bar H2 with TON 52, TOF 5 IT1 [68]. At intermediate conversions, the... 

In order to obtain adiponitrile, 2 should isomerize to 4, and not to the thermodynamically more stable 3 (stabilised by the energy of conjugation). The thermodynamic ratio is 2 3 4 = 20 78 1.6 [6], The isomerization of 2 to 4 happens to be favorably controlled by the kinetics of the reactions the reaction 2 to 4 reaches equilibrium, but the reaction 2 to 3 does not. Note that the nickel complex not only is responsible for the addition of HCN but that it is also capable of catalysing selectively the isomerisation. The final step is the addition of HCN to 4 to give 5, adiponitrile. 

Hydrocyanation of olefins and dienes is an extremely important reaction [32] (about 75 % of the world s adiponitrile production is based on the hydrocyanation of 1,3-butediene). Not surprisingly, already one of the first Rhone Poluenc patents on the use of water soluble complexes of TPPTS described the Ni-catalyzed hydration of butadiene and 3-pentenenitrile (Scheme 9.10). The aqueous phase with the catalyst could be recycled, however the reaction was found not sufficiently selective. 

Figure 5.28. In situ wet-ETEM of real-time catalytic hydrogenation of nitrile liquids over novel Co-Ru/Ti02 nanocatalysts, (a) Fresh catalyst with Co-Ru clusters (arrowed at C). The support is marked, e.g., at u. (b) Catalyst immersed in adiponitrile liquid and H2 gas in flowing conditions growth of hexamethylene diamine (HMD) layers (at the catalyst surface S in profile, arrowed) at 81 °C, confirmed by composition analysis and mass spectrometry, (c) ED pattern of HMD in (b) in liquid environments. Further growth is observed at 100 °C. The studies show that wet-ETEM can be used to design a catalytic process (after Gai 2002). (d) Scaled up reactivity data for novel Co-Ru/Ti02 nanocatalysts confirming wet-ETEM studies of high hydrogenation activity of the nanocatalyst (2). Plots 1 and 3 are the data for Raney-Ni complexes and Ru/alumina catalysts, respectively.

Among other nonaddition processes, adiponitrile may be manufactured by the direct hydrocyanation of 1,3-butadiene (DuPont process).169 172,187 196 A homogeneous Ni(0) complex catalyzes both steps of addition of HCN to the olefinic bonds (Scheme 6.4). The isomeric monocyano butenes (20 and 21) are first formed in a ratio of approximately 1 2. All subsequent steps, the isomerization of 20 to the desired 1,4-addition product (21), a further isomerization step (double-bond migration), and the addition of the second molecule of HCN, are promoted by Lewis acids (ZnCl2 or SnCl2). Without Lewis acids the last step is much slower then the addition of the first molecule of HCN. Reaction temperatures below 150°C are employed. 

Hydrogen cyanide can be added across olefins in the presence of Ni, Co, or Pd complexes (Scheme 56) (123). Conversion of butadiene to adiponitrile is a commercial process at DuPont Co. The reaction appears to occur via oxidative addition of hydrogen cyanide to a low-valence metal, olefin insertion to the metal-hydrogen bond, and reductive elimination of the nitrile product. The overall reaction proceeds with cis... 

The structure of 2AgN03-succinonitrile revealed the presence of complex cations, [AgNC(CH2)2CNAg]2+, and ionic nitrate ions.161 The Ag—N distances were 197 pm and the C—N bond distance was close to that expected for a triple bond (112 pm). In AgC104-2(adiponitrile) the structure was in the form of a two-dimensional polymer with the adiponitrile acting as a bridge between silver ions. The silver ion was tetrahedrally coordinated by four N atoms with Ag—N distances of —228 pm.163... 

DuPont currendy practices a butadiene-to-adiponitrile route based on direct addition of HCN to butadiene (6—9). It was first commercialized in 1971. All reactions are catalyzed by soluble, air and moisture sensitive, triarylphosphite-nickel(0) complexes. 

The hydrocyanation of butadiene is an important industrial route to adiponitrile (equation 163).602 Again, complex (131) is used as the catalyst for the reaction. The hydrocyanation of dienes proceeds mainly by 1,4-addition and r/ -allyl complexes are believed to be intermediates (Scheme 59).603 The l-cyano-2-butene is then isomerized to l-cyano-3-butene which undergoes further hydrocyanation to give adiponitrile.601"603... 

Nickel-catalysed addition of HCN to butadiene was developed by du Pont for adiponitrile production [81]. A Ni(0)-phosphite complex is used as the catalyst in the presence of Lewis acids. Oxidative addition of HCN to Ni(0), followed by insertion of butadiene, generates 7r-allyl intermediate 187. Reductive elimination of 187 yields 188 and 189, and isomerization of the double bond in 189 to the terminal position gives 4-pentenonitrile (190). Then, insertion of 190 to H—Ni—CN affords adiponitrile (191). 

Liquid/liquid extraction of the catalyst, as in the DuPont adiponitrile process, where the nickel complex is extracted out of the product mixture after the reaction, with a solvent (see Section 7.7). In Shell s SHOP process the soluble nickel catalyst is also extracted from the reaction medium with a highly polar solvent, and reused (see Section 7.4.1). 

Industrial uses of HCN are for synthesis of methyl methacrylate and to form adiponitrile (for adipic acid and nylon) by addition to 1,3-butadiene in the presence of nickel(O) phosphite complexes. Waste HCN is also oxidatively hydrolyzed to give oxamide for use as fertilizer. 

The mixture of dichlorobutcncs is heated with HCN or NaCN in the presence of copper cyano complexes (Equation (17)). As 3,4-di-cyanobutene rearranges to the required 1,4-isomcr under the hydrocyanation conditions, the overall yield remains economically acceptable the last step being tlie hydrogenation of dicyanobutene to adiponitrile. 

Table 8 includes copper(I) complexes of the dinitiiles sucdnonitrile, glutaronitrile and adiponitrile. The crystal structure shows linear C — C = N. .. Cu arrangements in the three cases each copper ion is surrounded tetrahedrally by four nitrile groups. Etndently, the nitrile lone pair orbitals act as the donor part in these EDA complexes. Since Cu(I) has the electronic configuration 3d , the 4s and 4p orbitals have to be considered as the acceptor orbitals (sp, tetrahedral). 

The most outstanding example for the applieation of homogeneously catalyzed hydrocyanation is the DuPont adiponitrile process. About 75 % of the world s demand for adiponitrile is covered by hydrocyanation of butadiene in the presence of nickel(O) phosphite species. This process is discussed for the addition of HCN to dienes as an example, because in this case a well-founded set of data is available. Though it was Taylor and Swift who referred to hydrocyanation of butadiene for the first time [45], it was to Drinkard s credit that this principle was fully exploited for the development of the DuPont adiponitrile process [18]. The overall process is described as the addition of two equivalents of HCN to butadiene in the presence of a tetrakisphosphite-nickel(O) catalyst and a Lewis acid promoter. A phosphine-containing ligand system for the catalyst is not suitable, since addition of HCN to the tetrakisphosphine-nickel complex results in the formation of hydrogen and the non-aetive dicyano complex [67], In general the reaction can... 

Adiponitrile s mechanism of toxicity is similar to cyanide because it can potentially liberate cyanide in the body spontaneously. It forms a stable complex with ferric iron in the cytochrome oxidase enzymes, thereby inhibiting cellular respiration. Cyanide affects primarily the central nervous system (CNS), producing early stimulation followed by depression. It initially stimulates the peripheral chemoreceptors (causing increased respiration) and the carotid bodies (thereby slowing the heart). Early CNS, respiratory, and myocardial depression result in decreased oxygenation of the blood and decreased cardiac output. These effects produce both stagnation and hypoxemic hypoxia in addition to cytotoxic hypoxia from inhibition of mitochondrial cytochrome oxidase. 

Hydrocyanation is the addition of HCN across a C=C bond. In 1971, Dupont reported a new process that added two equivalents of HCN, in an anti-Markovnikov manner, to 1,3-butadiene to yield adiponitrile (equation 9.38).96 The process is catalyzed overall by a Ni(0) triarylphosphite complex. 

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