RU2466135C1 - Method of producing organometallic nickel (iii) complexes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to organometallic chemistry and specifically to a method of producing organometallic nickel (III) complexes. The method is realised via oxidative bonding of an olefin to a cationic nickel (I) complex formed by oxidising bis(cyclooctadiene-1,5)nickel with boron trifluoride etherate. Formation of catalytically active organometallic nickel (III) complexes is carried out in molar ratio B:Ni=2:1.

EFFECT: invention considerably simplifies obtaining organometallic nickel (III) complexes which exhibit high catalytic activity with respect to olefins.

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Description

The invention relates to the field of organometallic chemistry, namely to the development of atom-economical methods for the synthesis of organometallic compounds, which are promising in creating breakthrough technologies in the field of metal complex catalysis [G.Wilke. // Angewandte Chemie International Edition in English, 1988, v. 27, No. 1, p. 185-206]. The catalytic conversions of unsaturated hydrocarbons (polymerization, isomerization, etc.) play a crucial role in the modern chemical industry. To date, most of the catalytic conversions of unsaturated hydrocarbons can be implemented using highly efficient metal complex catalysts. One of the key stages in the formation of the active center of a metal complex catalyst is the nucleation of a metal-carbon bond. Thus, one of the most important tasks in creating catalysts is the realization of conditions under which organometallic compounds are formed in high yield. A large number of methods for the formation of compounds with a metal-carbon bond are described in the world literature, in particular, in [P.W. Jolly, G.Wilke, The Organic Chemistry of Nickel, Academic Press, New York 1974, vol. 1, p.139 -146] sets forth in detail the principles of the formation of nickel-organic compounds. Undoubtedly, most of the described methods are effective and quite technologically advanced. A common disadvantage of the described methods is the need to use any other organometallic compounds at the initial stage of the formation of the nickel-carbon bond. In addition, in this case, compounds of another metal, for example, aluminum, lithium, etc. are invariably introduced into the system. A fundamentally different approach allows us to avoid the indicated drawbacks: the formation of organometallic nickel complexes from nickel π-complexes (0) by oxidative addition of olefin to the metal.

The closest known solution to a similar problem - the formation of organometallic nickel (IV) complexes without using organometallic compounds as stabilizing ligands, is the method of oxidative addition of (5Z, 11E) -dibenzo [a, e] cyclooctatetraen to Ni (COD) ₂ . In this case, a metallocyclic diamagnetic complex of nickel (IV) is formed in the system. Authors [M.Camesi, D. Bucella, JY-C. Chen, APRamirez, NJ Turro, C. Nuckolls, M. Steigerwald. // Angewandte Chemie International Edition in English, 2009, v. 48, No. 2, p. 290-294] there is a low catalytic activity of the obtained organometallic nickel complex, it should also be noted that (5Z, 11E) -dibenzo [a, e] cyclooctatetraen is an expensive laboratory synthesis product.

To eliminate these disadvantages is proposed in the following way. To form an organometallic complex of nickel (III) by oxidative addition of olefin to the cationic complex of nickel (I), while the cationic complex of nickel (I) is preformed by oxidation of bis (cyclooctadiene-1,5) nickel (hereinafter Ni (COD) ₂ ) with boron trifluoride etherate with a molar ratio of B: Ni = 2: 1. The method is atom-economical, since it is enough to introduce 2 parts of boron trifluoride etherate into the system, which is completely consistent with the one proved in [VVSaraev, PBKraikivskii, DAMatveev, SNZelinskii and K. Lammertsma. // Inorganica Chimica Acta., 2006, v. 359, p.2314-2320] by the mechanism of formation of cationic nickel (I) complexes. The reaction is carried out in a solution of toluene, benzene or cyclohexane. At the same time, paramagnetic organometallic nickel (III) complexes are formed in a system with a high yield, which exhibit high catalytic activity with respect to olefins. After formation, the nickel (III) complexes thus obtained are stable in solution for a long time, at least 3 days. When olefins (for example, propylene, cyclooctadiene-1.5 (hereinafter COD) or norbornene (hereinafter NB)) are introduced into the system, the polymerization reaction begins without any prior activation. Undoubtedly, such a method for the formation of catalytically active centers is revolutionary in nature and can significantly simplify and cheapen the formation of highly efficient catalysts, and also dramatically increases the waste-free processes.

Example 1

The reaction was carried out in a thermostatic glass vessel, allowing intensive mixing of the reaction medium, as well as creating and controlling the pressure of ethylene or argon. In the interaction between Ni (COD) ₂ and BF ₃ · ОЕt ₂ in an ethylene atmosphere (the solvent is toluene, benzene or cyclohexane, the solvent volume is 20-40 ml, the amount of Ni (COD) ₂ complex is 0.03-0.04 g, molar ratio B: Ni = 2: 1) at the initial moment of the reaction, an intense EPR 1 signal is recorded (Figure 1), from the cationic complex of nickel (I) [Saraev V.V., Kraikivsky PB, Matveev D.A., Wilms A.I. A method of producing cationic complexes of monovalent nickel. // RU 2400300 C2. Published on September 27th, 2010. Bull. No. 27], which is transformed into a new EPR 2 signal (Fig. 1). In the EPR 2 signal, the hyperfine structure (HFS) from two equivalent nuclei with spin I = 1/2 (g || = 1.987, g⊥ = 2.452, A || = 122.2G, A⊥ = 58.8G) is well resolved. Replacement of the signal on the signal 1 2 in the EPR spectrum is accompanied by a substitution of the bands in the IR spectrum of the anion BF ₄ ^- (1122-1050, 826 cm ^-1) in a group of bands with maxima at 1224, 1184, 1082 and 1030 cm ^-1, in which According to literature data, tetrafluoroborate bridge structures can be attributed to [Nakamoto K. IR and Raman spectra of inorganic and coordination compounds. M.: Mir Publishing House, 1991, 536 p.]. In order to elucidate the nature of STS in signal 2, experiments were carried out using deuteroethylene. The replacement of ordinary ethylene with deuteroethylene before the stage of mixing the components of the catalytic system did not affect the shape and intensity of the EPR 2 signal. Therefore, the HFS in signal 2 is not related to ethylene protons, but is due to two equivalent ¹⁹ F nuclei (I _F = 1/2) . This assumption is also supported by the large HFS constant, which is an order of magnitude higher than the known HFS constants with ¹ N for Ni (I) hydride complexes. Thus, the EPR 2 signal, which is recorded in an ethylene atmosphere, unambiguously indicates the formation of a close ion pair between the nickel cation and the BF ₄ ^- anion. The ratio between the components of the g-factor (g⊥> g || ≈2) is characteristic of Ni (I) ions with the 3d ⁹ electronic configuration in the trigonal field of ligands [Saraev V.V., Kraikivsky PB, Lazarev P.G. , Mjagmarsuren G., Weaver BC, Schmidt F.K. // Coordinate. chemistry. 1996, v.22, No. 9, pp. 655-662], as well as for Ni (III) ions with the 3d ⁷ electronic configuration in a strong tetragonal ligand field [Goodman B.A., Rayanor JB // Adv. Anorg. Chem. and Radiochem., 1970, v. 13, p. 135-362; Kuska HA, Rogers MT Electron Spin Resonance of First Row Transition Metal Complex Ions. Inerscience publishers, John Wiley and Sons, New York, 1968]. Strictly axial anisotropy of the g-factor is possible only if the ligands are equivalent in the equatorial plane. Exceptions are flat tetracoordination cis complexes with pairwise equivalent ligands [Ballhansen CJ Introduction to Ligand Field Theory. McGranw-Hill book company, INC. New York, San Francisco, Toronto, London, 1962]. Considering that only two equivalent F atoms enter the first coordination sphere of nickel, signal 2 should be attributed to the cis-structured flat tetracoordination complex Ni (III) (complex I):

Moreover, the metallocycle ®, which includes nickel (III), can be not only three-membered, but also five-membered or more (both substituted and not substituted), while the organic radical is a product of ethylene oligomerization.

Example 2

The same as example 1, only after reaching the maximum intensity of the EPR 2 signal, an excess of COD was introduced into the system, while a catalytic COD cyclodimerization reaction was observed, and in the EPR spectrum, at the beginning, the replacement of signal 2 by signal 1 is observed, and then as COD transforms reverse transformation occurs in the solution.

The example illustrates the catalytic activity of the formed organometallic nickel (III) complex without prior activation, the direct participation of the complex in the catalytic cycle (a change in the EPR signal), and the regeneration of the nickel (III) complex after the substrate has been used up (restoration of the EPR 2 signal).

Example 3

The reaction was carried out in a thermostatic glass vessel, allowing intensive mixing of the reaction medium, as well as creating and controlling argon pressure. In the interaction between Ni (COD) ₂ and BF ₃ · ОЕt ₂ in an argon atmosphere (the solvent is toluene, benzene or cyclohexane, the volume of the solvent is 20-40 ml, the amount of the Ni (COD) ₂ complex is 0.03-0.04 g, molar ratio B: Ni = 2: 1) at the initial moment of the reaction, an intense EPR 1 signal is recorded (Figure 2), from the cationic nickel complex (I), which is transformed into an EPR 3 signal (Figure 2) from the organometallic cationic nickel complex (I ) [Saraev V.V., Kraikivsky P.B., Matveev D.A., Wilms A.I. A method of producing cationic complexes of monovalent nickel. // RU 2400300 C2. Published on September 27th, 2010. Bull. No. 27]. The EPR 3 signal is stable in time in the absence of free olefins in the system. After transforming the EPR signal 1 into the EPR signal 3, norbornene was introduced into the system (NB: Ni = 50). After introducing 3 norbornene signal intensity drops rapidly and a new intense signal 4, which is well resolved from one STS nucleus with spin _^1/2. An EPR 4 signal containing a doublet is characterized by the following parameters: g _|| = 1,977, g _⊥ = 2,65, A _|| = 126G, A _⊥ = 51G.

In the system under study, there are only two types of nuclei with spin 1/2, these are ¹ H and ¹⁹ F nuclei. Analyzing the HFS, we can state that it belongs to the ¹⁹ F nucleus, since its value exceeds the known HFS constants from ¹ N by an order of magnitude hydride complexes of Ni (I).

Thus, signal 4 can be attributed to the metallocyclic complex of trivalent nickel with the electronic configuration d ⁷ associated with one fluorine atom and an organic cycle (complex II):

Example 4

The same as example 3, only after signal 4 was generated, a large amount of norbornene was introduced into the system (NB: Ni = 5000), while the norbornene polymerization proceeds according to the additive mechanism with an activity of 1480 kgNB / molNi · h. Example 4 illustrates the high activity of the formed organometallic complex of nickel (III) in the polymerization of a cyclic olefin by an additive mechanism.

Example 5

Same as Example 4, only a larger amount of boron trifluoride etherate was introduced into the system at the initial stage (B: Ni = 5). The activity of the system in the polymerization of norbornene was 1930 kgNB / molNi · h.

Example 5 illustrates the insignificant effect of increasing the B: Ni ratio on the activity of the formed nickel (III) complexes and proves that, using the proposed method, it is sufficient to introduce into the system two molar parts of boron trifluoride etherate with respect to nickel. Example 5 once again confirms the high potential for creating atom-economical catalytic systems using the proposed method for the formation of organometallic nickel (III) complexes.

The described method is a vivid example of the atom-economical formation of organometallic complexes of nickel (III) and opens up great opportunities for creating ideal catalytic systems that do not contain any "extra" chemical elements, in addition to those that are directly involved in the formation and stabilization of catalytically active centers.

The technical effect is a simplification of the method, increasing the yield of the target product, the cost of the process, the absence of impurities.

Claims (1)

The method of forming organometallic nickel (III) complexes by oxidative addition of olefin to a nickel (I) cationic complex formed by oxidation of bis (cyclooctadiene-1,5) nickel with boron trifluoride etherate, characterized in that the formation of catalytically active organometallic nickel (III) complexes is carried out at molar ratio B: Ni = 2: 1.

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