Thallium(I) Sandwich, Multidecker, and Ether Complexes Stabilized by Weakly-Coordinating Anions: A Spectroscopic, Structural, and Theoretical Investigation

Sarazin, Y, Hughes, D, Kaltsoyannis, N, Wright, JA and Bochmann, M (2007) Thallium(I) Sandwich, Multidecker, and Ether Complexes Stabilized by Weakly-Coordinating Anions: A Spectroscopic, Structural, and Theoretical Investigation. Journal of the American Chemical Society, 129 (4). pp. 881-894.

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Abstract

The reaction of thallium ethoxide with [H(OEt2)2][H2N{B(C6F5)3}2] in diethyl ether afforded [Tl(OEt2)3][H2N{B(C6F5)3}2] ( 2a ), [Tl(OEt2)4][H2N{B(C6F5)3}2] ( 2b ), or [Tl(OEt2)2][H2N{B(C6F5)3}2]·CH2Cl2 ( 2c ), depending on the reaction conditions. The dication in the hydrolysis product [Tl4(µ3-OH)2][H2N{B(C6F5)3}2]2·4CH2Cl2 consists of two bridging and two terminal Tl+ ions bound to triply bridging hydroxides. Heating Et2O complexes in toluene afforded [Tl(?6-toluene)n][H2N{B(C6F5)3}2] ( 4 , n = 2, 3), while C6Me6 addition gave the first thallium-C6Me6 adduct, [Tl(?6-C6Me6)2][H2N{B(C6F5)3}2]·1.5CH2Cl2 ( 5a ), a bent sandwich complex with very short Tl···centroid distances. These arene complexes show no close contacts between cations and anions. Displacement of toluene ligands by ferrocene gave [Tl2(FeCp2)3][H2N{B(C6F5)3}2]2·5CH2Cl2 ( 6 ) which contains the multidecker cations [Tl(FeCp2)]+ and [Tl(FeCp2)2]+ in a 1:1 ratio. By contrast, decamethylferrocene leads to electron transfer; the isolable thallium-ferrocene complexes may therefore be viewed as precursor complexes for this redox step. With 18-crown-6 the complexes [Tl(18-crown-6)2][H2N{B(C6F5)3}2] ( 11a ) and [Tl(18-crown-6)][H2N{B(C6F5)3}2]·2CH2Cl2 ( 11b ) were isolated. The structure of the latter shows an eight-coordinate thallium ion, where the coordination to the six oxygen donors in equatorial positions is completed by axial contacts to two F atoms of the counter anions. The bonding between thallium(I) and arenes was explored by density-functional theory (DFT) calculations. The optimized geometry of [Tl(tol)3]+ converged to a structure very similar to that obtained experimentally. Calculations on [Tl(C6Me6)2]+ ( 5b ) to establish whether a linear or bent geometry is the most stable revealed a very flat potential-energy surface for distortions of the Ctr(3)-Tl-Ctr(4) angle. Overall, there is very little energetic preference for one particular geometry over another above about 140°, in good agreement with the crystallographic geometry. The calculated Tl-arene interaction energies increase from 73.7 kJ mol-1 for toluene to 121.7 kJ mol-1 for C6Me6.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 02 Nov 2010 17:48
Last Modified: 20 Sep 2020 23:32
URI: https://ueaeprints.uea.ac.uk/id/eprint/10533
DOI: 10.1021/ja0657105

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