Jack Passmore

Approaching the gas-phase structures of [AgS8]+ and [AgS16]+ in the solid state

Upon treating elemental sulfur with [AgSbF(6)], [AgAl(hfip)(4)], [AgAl(pftb)(4)] (hfip=OCH(CF(3))(2), pftb =OC(CF(3))(3)) the compounds [Ag(S(8))(2)][SbF(6)] (1), [AgS(8)][Al(hfip)(4)] (2), and [Ag(S(8))(2)](+)[[Al(pftb)(4)](-) (3) formed in SO(2) (1), CS(2) (2), or CH(2)Cl(2) (3). Compounds 1-3 were characterized by single-crystal X-ray structure determinations: 1 by Raman spectroscopy, 2 and 3 by solution NMR spectroscopy and elemental analyses. Single crystals of [Ag(S(8))(2)](+)[Sb(OTeF(5))(6)](-) 4 were obtained from a disproportionation reaction and only characterized by X-ray crystal structure analysis. The Ag(+) ion in 1 coordinates two monodentate SbF(6) (-) anions and two bidentate S(8) rings in the 1,3-position. Compound 2 contains an almost C(4v)-symmetric [AgS(8)](+) moiety; this is the first example of an eta(4)-coordinated S(8) ring (d(Agbond;S)=2.84-3.00 A). Compounds 3 and 4, with the least basic anions, contain undistorted, approximately centrosymmetric Ag(eta(4)-S(8))(2) (+) cations with less symmetric eta(4)-coordinated S(8) rings (d(Agbond;S)=2.68-3.35 A). The thermochemical radius and volume of the undistorted Ag(S(8))(2) (+) cation was deduced as r(therm)(Ag(S(8))(2) (+))=3.378+ 0.076/-0.120 A and V(therm)(Ag(S(8))(2) (+))=417+4/-6 A(3). AgS(8) (+) and several isomers of the Ag(S(8))(2) (+) cation were optimized at the BP86, B3LYP, and MP2 levels by using the SVP and TZVPP basis sets. An analysis of the calculated geometries showed the MP2/TZVPP level to give geometries closest to the experimental data. Neither BP86 nor B3LYP reproduced the longer weak dispersive Agbond;S interactions in Ag(eta(4)-S(8))(2) (+) but led to Ag(eta(3)-S(8))(2) (+) geometries. With the most accurate MP2/TZVPP level, the enthalpies of formation of the gaseous [AgS(8)](+) and [Ag(S(8))(2)](+) cations were established as Delta(f)H(298)([Ag(S(8))(2)](+), g)=856 kJ mol(-1) and Delta(f)H(298)([AgS(8)](+), g)=902 kJ mol(-1). It is shown that the [AgS(8)](+) moiety in 2 and the [AgS(8)](2) (+) cations in 3 and 4 are the best approximation of these ions, which were earlier observed by MS methods. Both cations reside in shallow potential-energy wells where larger structural changes only lead to small increases in the overall energy. It is shown that the covalent Agbond;S bonding contributions in both cations may be described by two components: i) the interaction of the spherical empty Ag 5s(0) acceptor orbital with the filled S 3p(2) lone-pair donor orbitals and ii) the interaction of the empty Ag 5p(0) acceptor orbitals with the filled S 3p(2) lone-pair donor orbitals. This latter contribution is responsible for the observed low symmetry of the centrosymmetric Ag(eta(4)-S(8))(2) (+) cation. The positive charge transferred from the Ag(+) ion in 1-4 to the coordinated sulfur atoms is delocalized over all the atoms in the S(8) ring by multiple 3p(2)-->3sigma* interactions that result in a small long-short-long-short Sbond;S bond-length alternation starting from S1 with the shortest Agbond;S length. The driving force for all these weak bonding interactions is positive charge delocalization from the formally fully localized charge of the Ag(+) ion.

Electron spin resonance study of CH3CNSSN˙, C6H5CNSSN˙, and SNSSN˙+ free radicals

Isotropic and powder e.s.r. spectra have been recorded for CH3[graphic omitted]˙, C6H5[graphic omitted]˙, and [graphic omitted]˙+. Isotropic labelling with nitrogen-15 and sulphur-33 has been accomplished for [graphic omitted]˙+ and it has been possible to prepare 33[graphic omitted]˙+. Sulphur-33 satellites have been observed for C6H5[graphic omitted]˙. MNDO and Gaussian 76 calculations have been used to calculate the minimum-energy structures of the radicals, while INDO calculations have provided values for the hyperfine coupling constants. Unfortunately, poor agreement was obtained between the latter and the corresponding experimental values. All the radicals dimerise in solution at low temperatures and we have been able to measure the energetics of dimerisation for C6H5[graphic omitted]˙ and [graphic omitted]˙+. The dimers exist as crystalline solids which contain readily detectable amounts of the monomeric free radical.

Paramagnetic liquids: the preparation and characterisation of the thermally stable radical ButCNSNS· and its quantitative photochemically symmetry allowed rearrangement to a second stable radical ButCNSSN

The new thermally stable paramagnetic liquid 5-t-butyl-1,3,2,4-dithiadiazolyl has been isolated in the dark and quantitatively photochemically isomerised to the paramagnetic liquid 5-t-butyl-2,3,1,4-dithiadiazolyl (non-systematic numbering for ease of comparison).

The high yield preparation, characterisation, and gas phase structure of the thermally stable CF3CSNSCCF3·, 4,5-bis(trifluoromethyl)-1,3,2-dithiazolyl and the X-ray crystal structure of benzo-1,3,2-dithiazolyl

The very thermally stable, but photochemically sensitive radical, 4,5-bis(trifluoromethyl)-1,3,2-dithiazolyl has been prepared, isolated, and fully characterised including a gas phase structure, and found to be paramagnetic in the liquid state at room temperature; the X-ray structure of benzo-1,3,2-dithiazolyl has been obtained for comparison.

Cyclododecasulfur as a ligand: from gas-phase experiments to the crystal structures of [Cu(S12)(S8)]+ and [Cu(S12)(CH2Cl2)]+.

Sulfur is the element with the largest number of modifications and usually exists as Sn ring molecules; those with n = 6–14, 18, and 20 have been structurally characterized. Thermodynamically, the two most stable rings are D4d S8 and D3d S12. [1a, 2] In contrast to the rich structural chemistry of elemental sulfur, the coordination chemistry of neutral sulfur molecules is underdeveloped and, to our knowledge, limited to [Ag(S8)] , [Ag(S8)2] , [{Rh2(O2CCF3)4}n(S8)m] [4a] and [Re2(m-X)2(CO)6(S8)] (X = Br, I). [4b] The coordination chemistry of the other chalcogens, Se and Te, is also restricted to few examples including [(OSO)AgSe6Ag(OSO)] and [(Se6Ag )n]. [5b] In agreement with this, the sulfur ring molecules usually undergo redox degradation when treated with transition metal cations, leading to simpler metal (poly-)sulfide complexes, rather than forming coordination compounds. However, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) gas phase investigations of transition metal monocations M with sulfur vapor (mainly S8) detected strong signals for [MSn] + complexes (n = 2–4, 6–8, 10, 12, and 14), suggesting that such coordination complexes can exist. However, it remains unclear, if the observed compounds are true coordination compounds of the Sn molecule or if M + oxidatively added to the S S bond, forming a (n + 1)-heterocycle. Recent quantum chemical studies on [MSn] + complexes (M = Li, Ca, V, Cu) suggested complexation of the metal cation to the ring structures. Another open question from the pioneering mass spectrometric study is whether the [MSn] + complexes contain a single Sn molecule or two (or more) smaller molecules Sx and Sy (x + y = n). For Ag + and S8, the mass spectrum showed two main signals, for [AgS8] + and [AgS16] , both of which were also fully characterized as [Ag(h-S8)] + and [Ag(h-S8)2] + incorporated in the corresponding salts in the solid state, using large and weakly coordinating anions (WCAs). These large WCAs create pseudo-gas-phase conditions in the solid state and the gas-phase reactivity was reproduced in the condensed phase. However, the reaction of Cu with S8 vapor is more challenging: [7a,b] MS experiments showed that the “natural” S8 complexes [CuS8] + and [CuS16] + were only observed within the first ten seconds of the experiment, after which [CuS12] + was the major peak. From the mass spectra it was not clear, if the S12 ring was present as a ligand or if the detected mass corresponded to one S4 and one S8, two S6, or even three S4 units. Figure 1 gives an overview of PBE0/TZVPP calculated [Cu(Sx)(Sy)] + (x + y = 12) species. These calculations indicate that that C3v [Cu(S12)] + is the most stable cation in the gas phase. To examine whether [Cu(S12)] + is also the global minimum in the condensed phase, we studied the reaction of cyclooctasulfur S8 with Cu + salts of WCAs. Reactions of Cu[AsF6] with S8 in solution in SO2 immediately gave an insoluble compound, which was fully characterized by Raman spectroscopy. By comparison with the structurally characterized homologues [Ag(h-S8)2] [EF6] (E = As, Sb), this material was assigned as [Cu(h-S8)2] [AsF6] (see the Supporting Information). Thus, using the classical weakly coordinating [AsF6] anion, the gas-phase behavior is not reproduced, probably as a result of the insolubility of [Cu(h-S8)2] [AsF6] , which may kinetically stabilize the S8 complex over the S12 complex. Larger WCAs of the type [Al(OR)4] (R = C(CF3)3) [9a]

The reaction of Li[Al(OR)4] R = OC(CF3)2Ph, OC(CF3)3 with NO/NO2 giving NO[Al(OR)4], Li[NO3] and N2O. The synthesis of NO[Al(OR)4] from Li[Al(OR)4] and NO[SbF6] in sulfur dioxide solution

NO[Al(OC(CF(3))(2)Ph)(4)] 1 and NO[Al(OC(CF(3))(3))(4)] 2 were obtained by the metathesis reaction of NO[SbF(6)] and the corresponding Li[Al(OR)(4)] salts in liquid sulfur dioxide solution in ca 40% (1) and 85% (2) isolated yield. 1 and 2, as well as Li[NO(3)] and N(2)O, were also given by the reaction of an excess of mixture of (90 mol%) NO, (10 mol%) NO(2) with Li[Al(OR)(4)] followed by extraction with SO(2). The unfavourable disproportionation reaction of 2NO(2)(g) to [NO](+)(g) and [NO(3)](-)(g)[DeltaH degrees = +616.2 kJ mol(-1)] is more than compensated by the disproportionation energy of 3NO(g) to N(2)O(g) and NO(2)(g)[DeltaH degrees =-155.4 kJ mol(-1)] and the lattice energy of Li[NO(3)](s)[U(POT)= 862 kJ mol(-1)]. Evidence is presented that the reaction proceeds via a complex of [Li](+) with NO, NO(2)(or their dimers) and N(2)O. NO(2) and Li[Al(OC(CF(3))(3))(4)] gave [NO(3)(NO)(3)][Al(OC(CF(3))(3))(4)](2), NO[Al(OC(CF(3))(3))(4)] and (NO(2))[Al(OC(CF(3))(3))(4)] products. The aluminium complex [Li[AlF(OC(CF(3))(2)Ph)(3)]](2) 3 was prepared by the thermal decomposition of Li[Al(OC(CF(3))(2)Ph)(4)]. Compounds 1 and 3 were characterized by single crystal X-ray structural analyses, 1-3 by elemental analyses, NMR, IR, Raman and mass spectra. Solid 1 contains [Al(OC(CF(3))(2)Ph)(4)](-) and [NO](+) weakly linked via donor acceptor interactions, while in the SO(2) solution there is an equilibrium between the associated [NO](+)[Al(OC(CF(3))(2)Ph)(4)](-) and separated solvated ions. Solid 2 contains essentially ionic [NO](+) and [Al(OC(CF(3))(3))(4)](-). Complex 3 consists of two [Li[AlF(OC(CF(3))(2)Ph)(3)]] units linked via fluorine lithium contacts. Compound 1 is unstable in the SO(2) solution and decomposes to yield [AlF(OC(CF(3))(2)Ph)(3)](-), [(PhC(CF(3))(2)O)(3)Al(mu-F)Al(OC(CF(3))(2)Ph)(3)](-) anions as well as (NO)C(6)H(4)C(CF(3))(2)OH, while compound 2 is stable in liquid SO(2). The [small nu](NO(+)) in 1 and [NO](+)(toluene)[SbCl(6)] are similar, implying similar basicities of [Al(OC(CF(3))(2)Ph)(4)](-) and toluene.

Preparation and crystal structures of (S7I)4S4(AsF6)6 and S4(AsF6)2·0.6SO2; a convenient synthesis of hexafluoroarsenate salts of chalcogen homoatomic cations

The oxidising ability of AsF5 is greatly enhanced by traces of bromine, and in its presence S4(AsF6)2·xSO2, (x⩽ 1) was prepared quantitatively from AsF5 and S8 in SO2; the X-ray structures of S4(AsF6)2·0.6SO2, and (S7I)4S4(AsF6)6 confirm the square planar geometry of S42+ in both salts, the former having a sulphur–sulphur bond distance of 2·014(4) and the latter of 1·98(1)A.

Preparation of CuAsF6 and Ni[AsF6]2.2SO2

Abstract Arsenic pentafluoride reacts with excess copper in sulphur dioxide to give CuAsF 6 . A similar reaction with elemental nickel yields Ni(AsF 6 ) 2 .2SO 2 , the structure of which is discussed. The X-ray powder diffraction photograph of CuAsF 6 was indexed on a rhombohedral unit cells a = 5.49±.01A, α = 55.7±.1°, V = 105.4A 3 , Z = 1, and is of the same structural type as LiSbF 6 showing that the cuprous ion is octahedrally surrounded by fluorines. Comparison of the unit cell volume of CuAsF 6 with other structurally similar hexafluoroarsenate salts shows that the effective volume of cuprous ion is small indicating substantial anion-cation interaction. Arsenic pentafluoride reacts with Monel in the presence of sulphur dioxide give a mixtures of CuAsF 6 and Ni[AsF 6 ] 2 .2SO 2 .

The preparation, characterization in solution of the 7π radical 1,2,4-triseleno-3,5-diazolylium and the 6π(1,2,4-triseleno-3,5-diazolium)2+ cations, and the X-ray crystal structures of (SeNSeNSe)2(AsF6)2 and SeNSeNSe(AsF6)2 containing the first stable binary selenium–nitrogen species

([graphic omitted])n(AsF6)2(n= 1,2) containing the first stable binary selenium–nitrogen species, have been prepared by the reaction of stoicheiometric quantities of Se4(AsF6)2(n= 2) or AsF5(n= 1 and 2) with Se4N4 in liquid SO2, and their structures determined by X-ray crystallography; in solution ([graphic omitted]e)2(AsF6)2 gives the indefinitely stable 7π radical [graphic omitted]e+˙(e.s.r. spectrum of frozen powder), and [graphic omitted](AsF6)2 the 6π [graphic omitted]e2+(Raman and 14N n.m.r. spectra).

The preparation of perfluoroethytellurium trifluoride, Trans perfluoroethyltellurium monochloride tetrafluoride, bis(perfluoroethyl) tellurium difluoride, and Trans bis(perfluoroethyl) tellurium tetrafluoride

Abstract : The authors report that bis(perfluoroethyl) ditelluride and chlorine monofluoride react in a 1:6 ratio at -78C to give C2F5TeF3 as well as small amounts of trans C2F5TeClF4 and TeClF5. Perfluoroethyl tellurium trifluoride is further oxidized by ClF at room temperature to give trans C2F5TeClF4 and TeClF5. Bis(perfluoroethyl) monotelluride and ClF in a 1:2 ratio at -78C give largely (C2F5)2TeF2, and in a 1:5 ratio at room temperature yield trans C2F5TeClF4, trans (C2F5)2TeF4, and TeClF5.