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The room-temperature stable CI3+ salts [CI3+[pftb](-)1 and [CI3]+[al-f-al](-) 2([pftb](-) = [Al(OC(CF3)3)4](-); [al-f-al](-) = [((CF3)3CO)3Al-F-Al(OC(CF3)3)3](-)) were prepared in quantitative yields from purified CI4 and the corresponding silver aluminates with total exclusion of light (NMR, IR, UV-VIS, X-ray diffraction). The isolated CI(3)(+) cation is trigonal planar with a sum of(I-C-I) = 360.0 degrees (1) and 359.9 degrees (2). Attempts to prepare CHI2+ and CH2I+ salts from CHI3 or CH2I2/Ag[pftb] mixtures remained unsuccessful; the reaction with CH2I2 leads to the formation of the adduct [Ag(CH2I2)3]+[pftb](-)3, while for HCI3, dismutation with formation of 1 as well as 3 was observed. All particles were also calculated at the MP2/TZVPP level to predict the vibrational and electronic spectra as well as to calculate the Gibbs free energies of all reactions (DeltaG degrees , gas phase and CH2Cl2 solution). Quantum chemical calculations were also used to investigate the stability of the [pftb](-) anion against the electrophilic attack of the CX3+ and CHnX3-n+ cations (X = F-I, n = 1-3). The strength of the Lewis acidity of these cations and of the isoelectronic boron halides BX()and BHnX3-n have been established on the basis of their fluoride ion affinities (FIAs). The FIAs of the carbon and the boron containing compounds show opposite trends, with fluorinated halomethyl cations being stronger acids than their heavier congeners but iodinated holoboranes being stronger acids than their lighter homologues.

This contributions shows with a series of ab initio MP2 and DFT (BP86 and B3-LYP) computations with large basis sets up to cc-pVQZ quality that the literature value of the std. enthalpy of depolymn. of 1/4Sb4F20(g) to give SbF5(g) (+18.5 kJ mol-1) [J. Fawcett, J. H. Holloway, R. D. Peacock, D. R. Russell, J. Fluorine Chem. 20 (1982) 9] is by about 50 kJ mol-1 in error and that the correct value of DrH Degdeploy. (1/4Sb4F20(g)) is +68 +- 10 kJ mol-1. We assign DrH Degdeploydepoly., DrH Deg, DrG Deg and DrG Deg values for SbnF5n with n = 2-4 and compare the results to available exptl. gas phase data. Esp. the MP2/TZVPP values obtained in an indirect procedure that rely on isodesmic reactions or the highly accurate compd. methods G2 and CBS-Q are in excellent agreement with the exptl. data, and reproduce also the fine exptl. details at temps. of 423 and 498 K. With these data and the addnl. calcn. of [SbnF5n+1]- (n = 1-4), we then assessed the fluoride ion affinities (FIAs) of SbnF5n(g), nSbF5(g), nSbF5(l) and the std. enthalpies of formation of SbnF5n(g) and [SbnF5n+1]-(g): FIA(SbnF5n(g)) = 514 (n = 1), 559 (n = 2), 572 (n = 3) and 580 (n = 4) kJ mol-1; FIA(nSbF5(g)) = 667 (n = 2), 767 (n = 3) and 855 (n = 4) kJ mol-1; FIA(nSbF5(l)) = 434 (n = 1), 506 (n = 2), 528 (n = 3) and 534 (n = 4) kJ mol-1. Error bars are approx. +-10 kJ mol-1. Also the related Gibbs energies were derived. DfH Deg([SbnF5n+1]-(g)) = -2064 +- 18 (n = 1), -3516 +- 25 (n = 2), -4919 +- 31 (n = 3) and -6305 +- 36 (n = 4) kJ mol-1. [on SciFinder (R)]

The unexpected but facile preparation of the silver salt of the least coordinating [(RO)3Al-F-Al(OR)3]- anion (R=C(CF3)3) by reaction of Ag[Al(OR)4] with one equivalent of PCl3 is described. The mechanism of the formation of Ag[(RO)3Al-F-Al(OR)3] is explained based on the available experimental data as well as on quantum chemical calculations with the inclusion of entropy and COSMO solvation enthalpies. The crystal structures of (RO)3Al--OC4H8, Cs+[(RO)2(Me)Al-F-Al(Me)(OR)2]-, Ag(CH2Cl2)3+[(RO)3Al-F-Al(OR)3]- and Ag(eta2-P4)2+[(RO)3Al-F-Al(OR)3]- are described. From the collected data it will be shown that the [(RO)3Al-F-Al(OR)3]- anion is the least coordinating anion currently known. With respect to the fluoride ion affinity of two parent Lewis acids Al(OR)3 of 685 kJ mol(-1), the ligand affinity (441 kJ mol(-1)), the proton and copper decomposition reactions (-983 and -297 kJ mol(-1)) as well as HOMO level and HOMO-LUMO gap and in comparison with [Sb4F21]-, [Sb(OTeF5)6]-, [Al(OR)4]- as well as [B(R(F))4]- (R(F)=CF3 or C6F5) the [(RO)3Al-F-Al(OR)3]- anion is among the best weakly coordinating anions (WCAs) according to each value. In contrast to most of the other cited anions, the [(RO)3Al-F-Al(OR)3] anion is available by a simple preparation in conventional inorganic laboratories. The least coordinating character of this anion was employed to clarify the question of the ground state geometry of the Ag(eta2-P4)2+ cation (D(2h), D(2) or D(2d)?). In agreement with computational data and NMR spectra it could be shown that the rotation along the Ag-(P-P-centroid) vector has no barrier and that the structure adopted in the solid state depends on packing effects which lead to an almost D(2h) symmetric Ag(eta2-P4)2+ cation (0 to 10.6 degrees torsion) for the more symmetrical [Al(OR)4]- anion, but to a D2 symmetric Ag(eta2-P4)2+ cation with a 44 degrees twist angle of the two AgP2 planes for the less symmetrical [(RO)3Al-F-Al(OR)3]- anion. This implies that silver back bonding, suggested by quantum chemical population analyses to be of importance, is only weak.

Prepn. of the title compd. (I) from starting materials CI4 and Ag[Al{OC(CF3)3}4](II) was performed with the complete exclusion of light and with carefully purified diiodine-free CI4, since CI4 decomps. within minutes in soln. in light with formation of I2 and other carbon iodides, and II reacts immediately with I2 to give yet unidentified decompn. products. With these precautions I was prepd. in quant. yield. According to calcns. at the MP2/TZVPP level and estn. of the sublimation and lattice enthalpies in a suitable cycle, we est. that the reaction is exothermic by -33 kJmol-1 in the gas phase and by -127 kJmol-1 in the solid state. In CH2Cl2 soln., I is dark blood red and in situ NMR reactions show only resonance signals for the CI3+ ion (d(13C)= 97 ppm; in SO2ClF: d(13C) = 95 ppm; calcd. value: d(13C) = 106 ppm) and the anion (d(13C) = 121.5 ppm (q); d(27A1)= 38.0 ppm). A CH2Cl2 soln. of I is stable for about 8 to 12 h at ambient temp. and much longer if stored at -30 or -78 DegC. Single crystals that appeared yellow as thin plates but black when thicker were grown at -78 DegC from cooled concd. CH2Cl2 solns. of I. The crystal structure detn. of a dark orthorhombic block of I showed that it contained isolated trigonal-planar CI3+ ions with a sum of I-C-I bond angles of 360.0 Deg (range: 118.8-122.1 Deg0) and Al{OC(CF3)3}4 ions. [on SciFinder (R)]

Insertion of the intermediately formed carbene-analogous PX24 ion (X = Br, I) into one of the P-P bonds of the P4 tetrahedron led to the P5X2+ ion - the 1st example of the previously unknown class of phosphorus-rich binary P-X cations. The crystal structure of [P5Br2]+[Al{OC(CF3)3}]- was detd. and mol. structure calcns. were performed on both the bromide and iodide analogs. [on SciFinder (R)]

In this study, we investigated the tetraalkylammonium salts of the weakly coordinating fluorinated alkoxyaluminates [pftb](-) ([Al(O(C(CF(3))(3))(4)](-)), [hfip](-) ([Al(OC(H)(CF(3))(2))(4)](-)) and [hftb](-) ([Al(OC(CH(3))(CF(3))(2))(4)](-)) in order to obtain information on their undisturbed spectral and structural properties, as well as to study their electrochemical behavior (i.e., conductivities in non-polar solvents and electrochemical windows). Several of the compounds qualify as ionic liquids with melting points as low as 42 degrees C for [NBu(4)](+)[hfip](-). Simple and almost quantitative metathesis reactions yielding these materials in high purity were developed. These [NR(4)](+) salts serve as model compounds for undisturbed anions and their vibrational spectra--together with simulated spectra based on quantum chemical DFT calculations--were used for the clear assignment of the anion bands. Besides, the ion volumes of the anions (V(ion)([pftb](-)) = 0.736 nm(3), V(ion)([hftb](-)) = 0.658 nm(3), V(ion)([hfip](-)) = 0.577 nm(3)) and their decomposition pathways in the mass spectrometric measurements have been established. The salts are highly soluble in non-polar solvents (up to 1.09 mol L(-1) are possible for [NBu(4)](+)[hftb](-) in CH(2)Cl(2) and 0.41 mol L(-1) for [NBu(4)](+)[hfip](-) in CHCl(3)) and show higher molar conductivities if compared to [NBu(4)](+)[PF(6)](-). The electrochemical windows of CH(2)Cl(2), CH(3)CN and 1,2-F(2)C(6)H(4) using the [NBu(4)](+) aluminate electrolytes are up to +0.5 V/-0.7 V larger than those using the standard [NBu(4)](+)[PF(6)](-).

A review on the available candidates in the quest for the least coordinating anion and a summary of new applications, available starting materials, and general strategies to introduce a WCA into a system. Some of the unusual properties of WCA salts such as high soly. in low dielec. media, pseudo gas-phase conditions in condensed phases, and the stabilization of weakly bound and low-charged complexes are rationalized on thermodn. grounds. Limits of the WCAs, i.e., anion coordination and decompn., are shown and a quantum chem. anal. of all types of WCAs is presented which allows the choice of a particular WCA to be based on quant. data from a wide range of different anions. [on SciFinder (R)]

Insertion of the intermediately formed carbene-analogous PX24 ion (X = Br, I) into one of the P-P bonds of the P4 tetrahedron led to the P5X2+ ion - the 1st example of the previously unknown class of phosphorus-rich binary P-X cations. The crystal structure of [P5Br2]+[Al{OC(CF3)3}]- was detd. and mol. structure calcns. were performed on both the bromide and iodide analogs. [on SciFinder (R)]