The photochemical substitution of benzene in [Cb*Co(C 6H6)]+ (Cb* = C4Me 4) with benzo-15-crown-5 (1) gives the corresponding π-complex [Cb*Co(η6-C6H4(OCH2CH 2C)CH2CH2)2O)]+ (2). A similar reaction with dibenzo-18-crown-6 (3) produces cation [Cb*Co(η6-C6H4(OCH2CH 2OCH2CH2O)2C6H 4)]+ (4). Arene exchange is reversible, and both 1 and 3 can be regenerated by irradiation of 2 and 4 with excess benzene. The reaction of [Cb*Co(C6H6)]+ with 0.5 equiv of 3 gives dinuclear complex [trans-Cb*Co(μ-η6, η6-C6H4(OCH2CH 2OCH2CH2O)2C6H 4)CoCb*]2+ (5). The structures of cations 4 and 5 were confirmed by X-ray diffraction. The electrochemical behavior of complexes prepared was studied. The sodium-binding ability of cobalt complexes 2,4, and 5 (determined by NMR titration; Ka = 2500, 800, and 50, respectively) was found to be much smaller than that of the free crown ethers 1 and 3 (K a, -200 000 and 5 000 000). DFT calculations suggest that this decrease is mainly due to electrostatic repulsion of Co+ and Na + centers. © 2008 American Chemical Society.
Perekalin, D.S., Babak, M.V., Novikov, V.V., Petrovskii, P.V., Lyssenko, K.A., Corsini, M., et al. (2008). A new approach to the photochemically controlled crown ethers: (Tetramethylcyclobutadiene)cobalt complexes with benzo-15-crown-5 and dibenzo-18-crown-6. ORGANOMETALLICS, 27(15), 3654-3658 [10.1021/om7002688].
A new approach to the photochemically controlled crown ethers: (Tetramethylcyclobutadiene)cobalt complexes with benzo-15-crown-5 and dibenzo-18-crown-6
Corsini M.;Zanello P.;
2008-01-01
Abstract
The photochemical substitution of benzene in [Cb*Co(C 6H6)]+ (Cb* = C4Me 4) with benzo-15-crown-5 (1) gives the corresponding π-complex [Cb*Co(η6-C6H4(OCH2CH 2C)CH2CH2)2O)]+ (2). A similar reaction with dibenzo-18-crown-6 (3) produces cation [Cb*Co(η6-C6H4(OCH2CH 2OCH2CH2O)2C6H 4)]+ (4). Arene exchange is reversible, and both 1 and 3 can be regenerated by irradiation of 2 and 4 with excess benzene. The reaction of [Cb*Co(C6H6)]+ with 0.5 equiv of 3 gives dinuclear complex [trans-Cb*Co(μ-η6, η6-C6H4(OCH2CH 2OCH2CH2O)2C6H 4)CoCb*]2+ (5). The structures of cations 4 and 5 were confirmed by X-ray diffraction. The electrochemical behavior of complexes prepared was studied. The sodium-binding ability of cobalt complexes 2,4, and 5 (determined by NMR titration; Ka = 2500, 800, and 50, respectively) was found to be much smaller than that of the free crown ethers 1 and 3 (K a, -200 000 and 5 000 000). DFT calculations suggest that this decrease is mainly due to electrostatic repulsion of Co+ and Na + centers. © 2008 American Chemical Society.
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https://hdl.handle.net/11365/1143939
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