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High valent element fluorosulfates and fluoride- fluorosulfates

University of British Columbia

The synthesis of the binary tetrakis(fluorosulfates) of the group 4 elements (Ti, Zr or Hf), all potential Lewis acids in fluorosulfuric acid (HSO3F), was carried out in order to extend the presently known conjugate superacid systems of the type HSO3F-M(SO3F)n. Metal oxidation by bis(fluorosulfuryl) peroxide (S206F2), in HSO3F, was the preferred route to these compounds. Although the polymeric M(SO3F)4 compounds were insoluble in HSO3F, they were found to be good fluorosulfate acceptors as was demonstrated by the synthesis of their ternary salts of the type Cs2[M(SO3F)6] (M = Ti, Zr or Hf). The resulting cesium salts are thermally stable up to 250°C and, as is evident from their vibrational spectra, are structurally similar to Cs2[M(SO3F)6] (M = Pt, Pd, Ge and Sn) reported previously. The synthetic use of fluorine fluorosulfate (FOSO2F) in the preparation of mixedfluoride fluorosulfates of the type EF,(SO3F),„, some of them potential Lewis acids in both HF and HSO3F, was explored. Reactions involved the oxidative addition of FOSO2F to a number of binary fluorides (SF4, SeF4 and AsF3) as well as the simultaneous fluorination and fluorosulfonation of elements (Br and I). The compounds obtained were studied by vibrational and NMR spectroscopy. Well-defined, monomeric compounds of the type EF5SO3F (E = S,Se) were formed in the reactions with SF4 and SeF4. The reactions with AsF3, I2 and Br2yielded nonstoichiometric materials of the type EFn(SO3F)5_„ (E = As, I) and BrFn(SO3F)3_,i;the nonstoichiometric property of these compounds has not been previously recognized. The oxidation of molybdenum pentafluoride (MoF5) by either S206F2 or FOSO2F produced MoOF3(SO3F) in addition to MoF6 and S205F2 rather than the expectedMoF5SO3F. The solvolysis of Mo2(CH3C00)2 in HSO3F resulted in the formation of the binuclear compound Mo2(SO3F)4, the only binary fluorosulfate of molybdenum known so far. Addition of acetonitrile (CH3CN) to this compound yielded Mo(SO3F)2(CH3CN)4. The fluorosulfate acceptor ability of MoF5 was demonstrated by the formation of Cs[MoF5SO3F]in a solid-state reaction between MoF5 and CsSO3F. The nucleophilicities of various fluoro- and oxy-acid anions in (CH3)2SnX2 salts have been studied in the past using M8ssbauer spectroscopy. All the examples studied had hexacoordinated tin, bidentate symmetrically bridging X-groups, and a linear C-Sn-C grouping. An attempt was made to extend the linear plot of the isomer shift (6) vs. the quadrupole coupling (SEQ),both of which correlate well with anion basicities, to dimethyltin(IV) carboxylates. To this end, the crystal structures of (CH3)2Sn(OOCR)2 (R = H, CF3 and CH3) were solved. The formate salt, (CH3)2Sn(OOCH)2, is a sheetpolymer with symmetrically bridging formate groups and a linear C-Sn-C group, and fits the correlation well. The trifluoroacetate group is unsymmetrically bridging in(CH3)2Sn(00CF3)2 and the acetate group is chelating in (CH3)2Sn(OOCH3)2. In both these compounds, the C-Sn-C moiety shows significant departure from linearity; this is reflected in their MOssbauer data which do not fall on the linear plot of S vs. SEQ. It appears that for00CR where R^H, the steric hindrance is increased to the point where a regular bridging structure cannot be obtained, and results in a distortion about the tin atom.

Thesis/Dissertation

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2008-09-10

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http://hdl.handle.net/2429/1814

Chemistry

University of British Columbia

UBCV

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