Reactivity of 2-methyl-3-butenenitrile in the presence of catalytic amounts of various cobalt complexes in ionic liquid
Graphical abstract
2M3BN in the presence of catalytic amount of several cobalt complexes was mainly isomerized into 2M2BN due to a easier activation of C–H bond instead of CCN bond.
With 3PN, the first example of a reversible cleavage of the CCN with complex derived from Co+ was evidenced.
Introduction
The rearrangement of 2-methyl-3-butenenitrile (2M3BN) into 3-pentenenitrile (3PN), the second step in the preparation of the adiponitrile, is often chosen as a model reaction in order to determine the catalytic performance of new ligands [1], [2] or new media, such as ionic liquid [3], [4]. Besides, this conversion occurring through a CCN bond cleavage (Fig. 1a), there is a possible isomerization of 2M3BN into the side product, 2-methyl-2-butenenitrile (2M2BN) which forms via CH activation (Fig. 1a).
The nickel(0) complexes clearly give the best results and the mechanism of the reaction of rearrangement of 2M3BN into 3PN with Ni0 catalyst (Fig. 1a) has been studied extensively [5], [6], [7], [8]. This mechanism is based on a Ni0 ↔ Ni2+ equilibrium. However, some authors claimed that cobalt complexes such as Co2(CO)8, Hg[Co(CO)4]2 and HCo[(P(OAr)3]4 {Ar = C6H5, o-CH3C6H4} present, for this reaction, analogous results to those of Ni0 [9], [10], [11], [12], [13].
Recently, we reported this catalytic rearrangement in the presence of phosphine complexes Ni0, in biphasic ionic liquid/organic solvent. Several neutral and ionic phosphines and ionic liquids have been tested. The best results in the conversion of 2M3BN (96%) and selectivity to 3PN (93%) were obtained for the catalytic system associating Ni(cod)2, (m-sulfophenyl)-diphenylphosphine sodium salt, [TPPMSNa] as the ligand and 1-butyl-2,3-dimethylimidazolium-bis(trifluoromethylsulfonyl)imide [BMMIm][NTf2] as the ionic liquid, in a biphasic ionic liquid/heptane solvent system. Partition experiments proved that the catalyst was immobilized in the ionic phase. TON (1020) and TOF (103 h−1) of the catalyst were measured [3], [4]. Recycling of the catalyst is possible but leads to an important deactivation which is related to the evolution of the nature of the ligand by ion exchange between the cation (Na+) of the ligand and the cation [BMMIm+] of the ionic liquid. This exchange induces a change in the nature of the ligand, thereby altering the nature of the catalyst and of the catalytic activity [14].
To immobilize a catalyst into ionic liquid, the catalyst ought to be ionic. Another approach is to use the ionic catalytic precursor in which the charge is on the metal center and with neutral ligand [15], [16], [17], [18], [19], [20].
In this paper, we report our attempts to realize the rearrangement 2M3BN into 3PN with a series of ionic cobalt complexes in the oxidation state Co1−, Co1+ and even Co0. The Co1− complex is isoelectronic with Ni0. On the other hand, the cationic complex Co1+ such as [(Ph2CHCHPPh2)2Co]+[ClO4]−, seems to be a possible candidate for this reaction due to the fact it reacts with HCN to give the cationic complex Co3+ [21]:
Section snippets
Synthesis of cobalt complexes
Several cobalt complexes (PPh3)3CoCl [22], 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridinecobaltmethyl, (BIP)CoMe [23], 1,1,1-tris(diphenyl-phosphinomethyl)ethane cobalt chloride, P3CoCl [24], HCo(P(OPh)3)4, NaCo(CO)4 [25], [Co(pyridine)6][Co(CO)4]2 [26], (η3allyl)Co(CO)2PPh3 [27] and H[Co{P(OPh)3}4] [28], [29] have been synthesized according to the procedure available in the literature.
The reaction of (PPh3)3CoCl with Li(N(SO2CF3)2, (LiNTf2), in the presence of bidentate phosphines, using
Conclusion
Several cobalt complexes in the oxidation states −1, 0, +1, synthesized (PPh3)3CoCl, [(Ph2PCH2CH2PPh2)2Co]+[NTf2]−, [(Ph2PCHCHPPh2)2Co]+[NTf2]−, P3CoCl, (BIP)CoMe, (η3allyl)Co(CO)3, (η3allyl)Co(CO)2PPh3, [P3Co]+[Co(CO)4]−, HCo(P(OPh)3)4, NaCo(CO)4, commercial Co2(CO)8 and CpCo(CO)2 were tested in the catalytic reaction of rearrangement of 2M3BN. Irrespective of the nature of cobalt complexes and the experimental conditions (presence of ligand [P(OPh)3 or pyridine], or/and of Lewis acid [ZnCl2,
Experimental
CoCl2·6H2O, zinc powder, 3-pentenenitrile, triphenylphosphine, CoBr2 and MeMgBr were purchased from Aldrich and used without further purification. Li(N(CF3SO2)2) was purchased from Solvionic and used as received.
Solvents were distilled using the appropriate drying agents: CaH2 for acetonitrile and dichloromethane, K2CO3 for chloroform and acetone, sodium for toluene and sodium/benzophenone for diethylether and tetrahydrofuran. 2-Methyl-3-butenenitrile was purchased from Rhodia Research Center,
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Rational design of efficient steric catalyst for isomerization of 2-methyl-3-butenenitrile
2020, Molecular CatalysisCitation Excerpt :In addition, there is a close relationship between the hydrocyanation and isomerization reactions on the typical catalysts such as NiL4 (L = tri-O-p-tolyl phosphite) [4]. To facilitate the development of the catalyst used in the DuPont process, the isomerization has been widely used as a model reaction for catalyst evaluation [5–8] and mechanistic investigation [9–12]. Due to its importance of the isomerization reaction for the DuPont process, it has been extensively studied [1,3].
Study of the reactivity of 2-methyl-3-butenenitrile with Ni(0)-N-heterocyclic carbene complexes
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2014, Bulletin of the Chemical Society of Japan