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Homoatomic Sulfur Cations 151 cations is governed by positive charge delocalization which enforces the for- mation of thermodynamically stable 3pp-3pp, p*-p*, and 3p2!3s* bonded species. In the gas phase and in solution the higher charged and in the solid state lattice stabilized Sn2+ dications (n=4, 8, 19) are unstable with respect to a dissociation into smaller cations, and recently it has been concluded that solutions of S82+ salts contain at least S62+, S5·+, and S7·+ or S42+, S4·+, S5·+, and S7·+ depending on whether halogen facilitator is present or not. With the help of quantum chemical calculations, which now already have predictive power, the experimental access to new sulfur cations in condensed phases is only a matter of time. Promising new preparative routes to salts of these new mono- or dications include the use of large and weakly coordinating an- ions, i.e., Al(OR)4 (R=C(CF3)3) [32, 33], that drastically change the lattice energies of all species in question and, therefore, should allow the synthesis of crystalline samples of hitherto in the solid state unknown sulfur cations. Acknowledgement This chapter is dedicated to Jack Passmore with whom I had the honor to spent my postdoctoral fellowship and who introduced me to the fascinating world of small but electronically delicate main group cations such as the homopolyatomic sulfur cat- ions. Thank you! This would have been impossible without the fine and bureaucracy-free sponsorship of the Alexander von Humboldt Stiftung in Bonn, Germany. References [1]. For reviews on sulfur and other chalocogen cations see: a) S. Brownridge, I. Krossing, J. Passmore, H. D. B. Jenkins, H. K. Roobottom, Coord. Chem. Rev. 2000, 197, 397; b) N. Burford , J. Passmore, J. C. P. Sanders, From Atoms to Polymers, Isoelectronic Analogies, 1989, pp. 53-108, Eds. J. F. Liebman and A. Greenburg, VCH; c) R. J. Gillespie, J. Passmore, Adv. Inorg. Radiochem. 1975, 17, 49; d) R. J. Gillespie, J. Chem. Soc. Rev. 1979, 8, 315; e) J. Beck, Angew. Chem. Int. Ed. Eng. 1994, 33, 163; f) J. Beck, Angew. Chem. Rev. 1997,163, 55-70; g) S. Ulvenlund, L. Bengtsson-Kloo, in Metal Clusters in Chemistry I, ed.: P. Braunstein, L. A. Oro, P. R. Raithby, Wiley-VCH, Weinheim, Germany, 1999, 561. [2]. C. F. Bucholz, Gehlens neues J. Chem. 1804, 3, 7. [3]. I. Krossing, J. Passmore, Inorg. Chem. (accepted). [4]. a) R. J. Gillespie, J. Passmore, Chem. Comm. 1969, 1333 ; b) R. J. Gillespie, J. Passmore, P. K. Ummat, O. C. Vaidya, Inorg. Chem. 1971,10, 1327; c) C. G.Davies, R. J. Gillespie, J. J. Park, J. Passmore, Inorg. Chem. 1971, 10, 2781. [5]. a) J. Passmore, G. Sutherland, P. S. White, J. Chem. Soc., Chem. Commun. 1980, 330; b) J. Passmore, G. W. Sutherland, P. S. White, Inorg. Chem. 1982, 21, 2717. [6]. R. C. Burns, R. J. Gillespie, J. F Sawyer, Inorg. Chem. 1980, 19, 1423. [7]. I.e. by ESR-spectroscopy using 92%33S enriched sulfur; see: H. S. Low, R. A. Beaudet, J. Am. Chem. Soc. 1976, 98, 3849. [8]. a) R. C. Burns, R. J. Gillespie, J. F Sawyer, Inorg. Chem. 1980, 19, 1423; b) J. Passmore, G. Sutherland, P. Taylor, T. K. Whidden, P. S. White, Inorg. Chem. 1981, 20, 3839. [9]. M. P. Murchie, J. Passmore, G. W. Sutherland, R. Kapoor, Dalton Trans. 1992, 503. [10]. However, recently a sample of crystalline S8(AsF6)2 was prepared that was red in trans- mitted but blue in reflected light.[23] The colors and UV-Vis spectra of sulfur cations were also the focus of much recent work; see [3]. [11]. T. S. Cameron, H. K. Roobottom, I. Dionne, J. Passmore, H. D. B. Jenkins, Inorg. Chem. 2000, 39, 2042. [12]. R. Faggiani, R. J. Gillespie, J. F Sawyer, J. E. Vekris, Acta Cryst. 1989, C45, 1847.PDF Image | Topics in Current Chemistry
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