The syntheses of carbocations by use of the noble-gas oxidant, [XeOTeF5][Sb(OTeF5)6]: the syntheses and characterization of the CX3+ (X = Cl, Br, OTeF5) and CBr(OTeF5)2+ cations and theoretical studies of CX3+ and BX3 (X = F, Cl, Br, I, OTeF5)

The CCl(3)(+) and CBr(3)(+) cations have been synthesized by oxidation of a halide ligand of CCl(4) and CBr(4) at -78 degrees C in SO(2)ClF solvent by use of [XeOTeF(5)][Sb(OTeF(5))(6)]. The CBr(3)(+) cation reacts further with BrOTeF(5) to give CBr(OTeF(5))(2)(+), C(OTeF(5))(3)(+), and Br(2). The [XeOTeF(5)][Sb(OTeF(5))(6)] salt was also found to react with BrOTeF(5) in SO(2)ClF solvent at -78 degrees C to give the Br(OTeF(5))(2)(+) cation. The CCl(3)(+), CBr(3)(+), CBr(OTeF(5))(2)(+), C(OTeF(5))(3)(+), and Br(OTeF(5))(2)(+) cations and C(OTeF(5))(4) have been characterized in SO(2)ClF solution by (13)C and/or (19)F NMR spectroscopy at -78 degrees C. The X-ray crystal structures of the CCl(3)(+), CBr(3)(+), and C(OTeF(5))(3)(+) cations have been determined in [CCl(3)][Sb(OTeF(5))(6)], [CBr(3)][Sb(OTeF(5))(6)].SO(2)ClF, and [C(OTeF(5))(3)][Sb(OTeF(5))(6)].3SO(2)ClF at -173 degrees C. The CCl(3)(+) and CBr(3)(+) salts were stable at room temperature, whereas the CBr(n)(OTeF(5))(3-n)(+) salts were stable at 0 degrees C for several hours. The cations were found to be trigonal planar about carbon, with the CCl(3)(+) and CBr(3)(+) cations showing no significant interactions between their carbon atoms and the fluorine atoms of the Sb(OTeF(5))(6)(-) anions. In contrast, the C(OTeF(5))(3)(+) cation interacts with an oxygen of each of two SO(2)ClF molecules by coordination along the three-fold axis of the cation. The solid-state Raman spectra of the Sb(OTeF(5))(6)(-) salts of CCl(3)(+) and CBr(3)(+) have been obtained and assigned with the aid of electronic structure calculations. The CCl(3)(+) cation displays a well-resolved (35)Cl/(37)Cl isotopic pattern for the symmetric CCl(3) stretch. The energy-minimized geometries, natural charges, and natural bond orders of the CCl(3)(+), CBr(3)(+), CI(3)(+), and C(OTeF(5))(3)(+) cations and of the presently unknown CF(3)(+) cation have been calculated using HF and MP2 methods have been compared with those of the isoelectronic BX(3) molecules (X = F, Cl, Br, I, and OTeF(5)). The (13)C and (11)B chemical shifts for CX(3)(+) (X = Cl, Br, I) and BX(3) (X = F, Cl, Br, I) were calculated by the GIAO method, and their trends were assessed in terms of paramagnetic contributions and spin-orbit coupling.     

Synthesis, characterization, and application of two Al(OR(F))3 Lewis superacids

We report herein the synthesis and full characterization of the donor-free Lewis superacids Al(OR(F))(3) with OR(F) = OC(CF(3))(3) (1) and OC(C(5)F(10))C(6)F(5) (2), the stabilization of 1 as adducts with the very weak Lewis bases PhF, 1,2-F(2)C(6)H(4), and SO(2), as well as the internal C-F activation pathway of 1 leading to Al(2)(F)(OR(F))(5) (4) and trimeric [FAl(OR(F))(2)](3) (5, OR(F) = OC(CF(3))(3)). Insights have been gained from NMR studies, single-crystal structure determinations, and DFT calculations. The usefulness of these Lewis acids for halide abstractions has been demonstrated by reactions with trityl chloride (NMR; crystal structures). The trityl salts allow the introduction of new, heteroleptic weakly coordinating [Cl-Al(OR(F))(3)](-) anions, for example, by hydride or alkyl abstraction reactions.     

Isolated cationic crown ether complexes of gallium(I) and indium(I)

The recently reported homologous low-valent indium and gallium salts M(+)[Al(OR(F))(4)](-) (M = Ga, In; R(F) = C(CF(3))(3)) were used to extend the coordination chemistry of Ga(I) and In(I) to the isolated [18]crown-6 complexes [M([18]crown-6)(PhF)(2)](+)[Al(OR(F))(4)](-) in fluorobenzene solution (PhF = C(6)H(5)F). In contrast to known ion-paired compounds for M = In, our complexes are undisturbed and in the solid state free of contacts to the anion. A peculiar combination of very weak η(1)- and η(6)-coordination to the PhF-solvent was observed that allows speculation about the presence of a stereochemically active lone pair at M(I). Structure and energetics of these novel salts were rationalized on the basis of DFT calculations.     

Univalent gallium and indium phosphane complexes: from pyramidal M(PPh3)3(+) to carbene-analogous bent M(PtBu3)2(+) (M=Ga, In) complexes

In a new oxidative route, Ag(+)[Al(OR(F))(4)](-) (R(F)=C(CF(3))(3)) and metallic indium were sonicated in aromatic solvents, such as fluorobenzene (PhF), to give a precipitate of silver metal and highly soluble [In(PhF)(n)](+) salts (n=2, 3) with the weakly coordinating [Al(OR(F))(4)](-) anion in quantitative yield. The In(+) salt and the known analogous Ga(+)[Al(OR(F))(4)](-) were used to synthesize a series of homoleptic PR(3) phosphane complexes [M(PR(3))(n)](+), that is, the weakly PPh(3)-bridged [(Ph(3)P)(3)In-(PPh(3))-In(PPh(3))(3)](2+) that essentially contains two independent [In(PPh(3))(3)](+) cations or, with increasing bulk of the phosphane, the carbene-analogous [M(PtBu(3))(2)](+) (M=Ga, In) cations. The M(I)-P distances are 27 to 29 pm longer for indium, and thus considerably longer than the difference between their tabulated radii (18 pm). The structure, formation, and frontier orbitals of these complexes were investigated by calculations at the BP86/SV(P), B3LYP/def2-TZVPP, MP2/def2-TZVPP, and SCS-MP2/def2-TZVPP levels.     

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.     

2,6-Mes(2)C(6)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-) (Mes = 2,4,6-Me(3)C(6)H(2)): A compound containing a linear unsolvated two-coordinate gallium cation

The title compound [2,6-Mes(2)C(2)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-), 1, containing a linear two-coordinate gallium cation, has been obtained by metathesis reaction of [2,6-Mes(2)C(2)H(3)](2)GaCl with 2 equiv of Li[Al(OCH(CF(3))(2))(4)] in C(6)H(5)Cl solution at room temperature. Compound 1 has been characterized by (1)H, (13)C((1)H), (19)F, and (27)Al NMR spectroscopy and X-ray crystallography. Compound 1 consists of isolated [2,6-Mes(2)C(6)H(3)](2)Ga(+) cations and Li[Al(OCH(CF(3))(2))(4)](2)(-) anions. The C-Ga-C angle is 175.69(7) degrees, and the Ga-C distances are 1.9130(14) and 1.9145(16) A. The title compound is remarkably stable, is only a weak Lewis acid, and polymerizes cyclohexene oxide.     

Synthesis and characterization of methylammonium borohydride

A new borohydride, [CH(3)NH(3)](+)[BH(4)](-), has been synthesized through the metathesis of CH(3)NH(3)F and NaBH(4) in methylamine. Room-temperature X-ray diffraction studies have shown that [CH(3)NH(3)](+)[BH(4)](-) adopts a tetragonal unit cell with considerable hydrogen mobility similar to that observed in NH(3)BH(3). The kinetics and thermodynamics of hydrogen release have been investigated and were found to follow a similar pathway to that of [NH(4)](+)[BH(4)](-). Decomposition of [CH(3)NH(3)](+)[BH(4)](-) occurred slowly at room temperature and rapidly at ca. 40 °C to form [BH(2)(CH(3)NH(2))(2)](+)[BH(4)](-), the methylated analogue of the diammoniate of diborane. The decomposition has been investigated by means of in situ X-ray diffraction and solid state (11)B NMR spectroscopy and occurred in the absence of any detectable intermediates to form crystalline [BH(2)(CH(3)NH(2))(2)](+)[BH(4)](-). [(CH(3))(2)NH(2)](+)[BH(4)](-) and [BH(2){(CH(3))(2)NH}(2)](+)[BH(4)](-) have also been synthesized through analogous routes, indicating a more general applicability of the synthetic method.     

Synthesis and characterization of the first examples of perfluoroalkyl-substituted trialkyloxonium salts, [(CH3)2OCF3]+[Sb2F11]- and [(CH3)2OCF(CF3)2]+[Sb2F11]-

In the superacidic HF/SbF(5) system, methyl trifluoromethyl ether forms at -78 degrees C the new tertiary oxonium salt [(CH(3))(2)OCF(3)](+)[Sb(2)F(11)](-), which was characterized by Raman and multinuclear NMR spectroscopy and its crystal structure. The same oxonium salt was also obtained by methylation of CH(3)OCF(3) with CH(3)F and SbF(5) in HF solution at -30 to -10 degrees C. Replacement of one methyl group in the trimethyloxonium cation by the bulkier and more electronegative trifluoromethyl group increases the remaining O-CH(3) bond lengths by 0.037(1) A and the sum of the C-O-C bond angles by about 4.5 degrees. Methylation of CH(3)OCF(CF(3))(2) with CH(3)F in HF/SbF(5) solution at -30 degrees C produces [(CH(3))(2)OCF(CF(3))(2)](+)[Sb(2)F(11)](-). The observed structure and vibrational and NMR spectra were confirmed by theoretical studies at the B3LYP/6-311++G(2d,2p) and the MP2/6-311++G(2d,p) levels.     

PX4+, P2X5+, and P5X2+ (X=Br,I) salts of the superweak Al(OR)4- anion [R=C(CF3)3

PX(4) (+)[Al(OR)(4)](-) (X=I: 1 a, X=Br: 1 b) was prepared from X(2), PX(3), and Ag[Al(OR)(4)] [R=C(CF(3))(3)] in CH(2)Cl(2) at -30 degrees C in 69-86 % yield. P(2)X(5) (+) salts were prepared from 2 PX(3) and Ag[Al(OR)(4)] in CH(2)Cl(2) at -30 degrees C yielding almost quantitatively P(2)X(5) (+)[Al(OR)(4)](-) (X=I: 3 a, X=Br: 3 b). The phosphorus-rich P(5)X(2) (+) salts arose from the reaction of cold (-78 degrees C) mixtures of PX(3), P(4), and Ag[Al(OR)(4)] giving P(5)X(2) (+)[Al(OR)(4)](-) (X=I: 4 a, X=Br: 4 b) with a C(2v)-symmetric P(5) cage. Silver salt metathesis presumably generated unstable PX(2) (+) cations from PX(3) and Ag[Al(OR)(4)] (X=Br, I) that acted as electrophilic carbene analogues and inserted into the Xbond;X (Pbond;X/Pbond;P) bond of X(2) (PX(3)/P(4)) leading to the highly electrophilic and CH(2)Cl(2)-soluble PX(4) (+) (P(2)X(5) (+)/P(5)X(2) (+)) salts. Reactions that aimed to synthesize P(2)I(3) (+) from P(2)I(4) and Ag[Al(OR)(4)] instead led to anion decomposition and the formation of P(2)I(5)(CS(2))(+)[(RO)(3)Al-F-Al(OR)(3)](-) (5). All salts were characterized by variable-temperature solution NMR studies (3 b also by (31)P MAS NMR), Raman and/or IR spectroscopy as well as X-ray crystallography (with the exception of 4 a). The thermochemical volumes of the Pbond;X cations are 121 (PBr(4) (+)), 161 (PI(4) (+)), 194 (P(2)Br(5) (+)), 271 (P(2)I(5) (+)), and 180 A(3) (P(5)Br(2) (+)). The observed reactions were fully accounted for by thermochemical calculations based on (RI-)MP2/TZVPP ab initio results and COSMO solvation enthalpy calculations (CH(2)Cl(2) solution). The enthalpies of formation of the gaseous Pbond;X cations were derived as +764 (PI(4) (+)), +617 (PBr(4) (+)), +749 (P(2)I(5) (+)), +579 (P(2)Br(5) (+)), +762 (P(5)I(2) (+)), and +705 kJ mol(-1) (P(5)Br(2) (+)). The insertion of the intermediately prepared carbene analogue PX(2) (+) cations into the respective bonds were calculated, at the (RI-)MP2/TZVPP level, to be exergonic at 298 K in CH(2)Cl(2) by Delta(r)G(CH(2)Cl(2))=-133.5 (PI(4) (+)), -183.9 (PBr(4) (+)), -106.5 (P(2)I(5) (+)), -81.5 (P(2)Br(5) (+)), -113.2 (P(5)I(2) (+)), and -114.5 kJ mol(-1) (P(5)Br(2) (+)).     

HCB11(CF3)(n)F(11-n)-: inert anions with high anodic oxidation potentials

Cs salts of four of the title anions were prepared by fluorination of salts of partly methylated (n = 11, 10) or partly methylated and partly iodinated (n = 6, 5) CB(11)H(12)(-) anions. The CH vertex is acidic, and in the unhindered anion with n = 6 it has been alkylated. Neat Cs(+)[1-H-CB(11)(CF(3))(11)](-) is as treacherously explosive as Cs(+)[CB(11)(CF(3))(12)](-), but no explosions occurred with the salts of the other three anions. BL3YP/6-31G* gas-phase electron detachment energies of the title anions are remarkably high, 5-8 eV. Treated with NiF(3)(+) in anhydrous liquid HF at -60 °C, anions with n = 11 or 10 resist oxidation, whereas anions with n = 6 or 5 are converted to colored EPR-active species, presumably the neutral radicals [HCB(11)(CF(3))(n)F(11-n)](?). These are stable for hours at -60 °C after extraction into cold perfluorohexane or perfluorotri-n-butylamine solutions. On warming to -20 °C in a Teflon or quartz tube, the color and EPR activity disappear, and the original anions are recovered nearly quantitatively, suggesting that the radicals oxidize the solvent.     

Synthesis and reactivity of bridging and terminal hydrosulfido palladium and platinum complexes. Crystal structures of [NBu4]2[(Pt(c6F5)2(mu-SH)]2], [Pt(C6F5)2(PPh3)[S(H)AgPPh3]], and [Pt(C6F5)2(PPh3)[S(AuPPh3)2]

The reactions of the hydroxo complexes [M(2)R(4)(mu-OH)(2)](2)(-) (M = Pd, R = C(6)F(5), C(6)Cl(5); M = Pt, R = C(6)F(5)), [[PdR(PPh(3))(mu-OH)](2)] (R = C(6)F(5), C(6)Cl(5)), and [[Pt(C(6)F(5))(2)](2)(mu-OH)(mu-pz)](2-) (pz = pyrazolate) with H(2)S yield the corresponding hydrosulfido complexes [M(2)(C(6)F(5))(4)(mu-SH)(2)](2-), [[PdR(PPh(3))(mu-SH)](2)], and [[Pt(C(6)F(5))(2)](2)(mu-SH)(mu-pz)](2-), respectively. The monomeric hydrosulfido complexes [M(C(6)F(5))(2)(SH)(PPh(3))](-) (M = Pd, Pt) have been prepared by reactions of the corresponding binuclear hydrosulfido complexes [M(2)(C(6)F(5))(4)(mu-SH)(2)](2-) with PPh(3) in the molar ratio 1:2, and they can be used as metalloligands toward Ag(PPh(3))(+) to form the heterodinuclear complex [(C(6)F(5))(2)(PPh(3))[S(H)AgPPh(3)]], and toward Au(PPh(3))(+) yielding the heterotrinuclear complexes [M(C(6)F(5))(2)(PPh(3))[S(AuPPh(3))(2)]]. The crystal structures of [NBu(4)](2)[[Pt(C(6)F(5))(2)(mu-SH)](2)], [Pt(C(6)F(5))(2)(PPh(3))[S(H)AgPPh(3)]], and [Pt(C(6)F(5))(2)(PPh(3))[S(AuPPh(3))(2)]] have been established by X-ray diffraction and show no short metal-metal interactions between the metallic centers.     

Mechanistic studies on the B(C(6)F(5))(3) catalyzed allylstannation of aromatic aldehydes with ortho donor substituents

Mechanistic studies on the B(C(6)F(5))(3) catalyzed allylstannation of isomeric substituted benzaldehydes are reported. Confirming a report by Maruoka et al., good (5:1) to excellent (>20:1) selectivities for ortho over para isomers are observed when 1:1 mixtures (X = OMe, Cl, F, OTBS) are allylstannated with C(3)H(5)SnBu(3) in the presence of B(C(6)F(5))(3) (2.5% per CHO). The best selectivities are observed for the anisaldehydes. Multinuclear NMR studies on solutions of B(C(6)F(5))(3) and C(3)H(5)SnBu(3) (1:1 to 1:5) show that the borane abstracts the allyl group from the organotin reagent, forming an adduct (C(6)F(5))(3)B...CH(2)CHCH(2)SnBu(3), 1, or ion pair [(C(6)F(5))(3)BCH(2)CH=CH(2)](-)[Bu(3)SnCH(2)CHCH(2)SnBu(3)](+), 2, depending on the reagent ratio. These compounds are important in the mechanism of Lewis acid catalyzed 1,3-isomerization of substituted allyl stannanes. When allyltin reagent is added to solutions of B(C(6)F(5))(3) and ortho-anisaldehyde (1:5) at -60 degrees C, conversion to the stannylium ion pair [Bu(3)Sn(ortho-anisaldehyde)(2)](+)[o-ArCH(allyl)OB(C(6)F(5))(3)](-), o,o-4, is observed. The structure of this species was confirmed by (1)H, (11)B, (19)F, and (119)Sn NMR spectroscopy and by forming related ion pairs (o-5 and o,o-5) utilizing the [B(C(6)F(5))(4)](-) counteranion via reaction of [Bu(3)Sn](+)[B(C(6)F(5))(4)](-) with aldehyde. The anion in o,o-4 is formed via direct allylation of the ortho-anisaldehyde/B(C(6)F(5))(3) adduct o-3, while the cation arises upon aldehyde ligation of the resulting tributylstannylium ion. The crystal structure of the related derivative ortho-C(6)H(4)(OMe)CHO x SnMe(3)BF(4), 6, showed that the aldehyde binds the tin nucleus only through the carbonyl oxygen. Similar reactions using para-anisaldehyde show that formation of p,p-4 occurs at a much slower rate, again demonstrating the preference for the ortho substituted substrates. For similar experiments using benzophenone, however, formation of the ion pair [Bu(3)Sn(Ph(2)CO)(2)](+)[(C(3)H(5))B(C(6)F(5))(3)](-), 8, was observed, illustrating the differences subtle changes in substrate can bring. Ion pair 8 is formed via the trapping of 1 by the benzophenone substrate. In the presence of excess aldehyde and allyltin reagent, ion pair o,o-4 catalyzes the allylstannation of aldehyde to give the product stannyl ether. Several lines of experimental evidence suggest this is the true catalyst in the system. The chemoselectivity observed thus does not rely on classical chelation control in any way. Rather, we propose that the ortho donor group stabilizes the developing positive charge at the beta carbon of the allyl group and the tin atom during the allylation event. This stabilization renders the ortho substituted substrates kinetically favored toward allylation irrespective of the Lewis acid employed.     

Structure of the SO(2)F(-) anion, a problem case

Recently, room-temperature crystal structures of SO(2)F(-) in its K(+) and Rb(+) salts were published in Z. Anorg. Allg. Chem. 1999, 625, 385 and claimed to represent the first reliable geometries for SO(2)F(-). However, their almost identical S-O and S-F bond lengths and O-S-O and O-S-F bond angles are in sharp contrast to the results from theoretical calculations. To clarify this discrepancy, the new [(CH(3))(2)N](3)SO(+) and the known [N(CH(3))(4)(+)], [(CH(3))(2)N](3)S(+), and K(+) salts of SO(2)F(-) were prepared and their crystal structures studied at low temperatures. Furthermore, the results from previous RHF and MP2 calculations were confirmed at the RHF, B3LYP, and CCSD(T) levels of theory using different basis sets. It is shown that all the SO(2)F(-) salts studied so far exhibit varying degrees of oxygen/fluorine and, in some cases, oxygen-site disorders, with [(CH(3))(2)N](3)SO(+)SO(2)F(-) at 113 K showing the least disorder with r(S-F) - r(S-O) = 17 pm and angle(O-S-O) - angle(F-S-O) = 6 degrees. Refinement of the disorder occupancy factors and extrapolation of the observed bond distances for zero disorder resulted in a geometry very close to that predicted by theory. The correctness of the theoretical predictions for SO(2)F(-) is further supported by the good agreement between the calculated and the experimentally observed vibrational frequencies and their comparison with those of isoelectronic ClO(2)F. A normal coordinate analysis of SO(2)F(-) confirms the weakness of the S-F bond with a stretching force constant of only 1.63 mdyn/A and shows that there is no highly characteristic S-F stretching mode. The S-F stretch strongly couples with the SO(2) deformation modes and is concentrated in the two lowest a' frequencies.     

Products, rate constants and mechanisms of gas-phase reactions of CX(3)(+), CX(2)(+), CX(+) (X = F and/or Cl) and Cl(+) with 1,1,1- and 1,1,2-trichlorotrifluoroethane.

The gas-phase ion chemistry of 1,1,1- and 1,1,2-trichlorotrifluoroethane was investigated with an ion trap mass spectrometer. Following electron ionization both compounds (M) fragment to [M - Cl](+), CX(3)(+), CX(2)(+), CX(+) (X = F and/or Cl) and Cl(+). The reactivity of each of these fragments towards their neutral precursors was studied to obtain product and kinetic data. Whereas [M - Cl](+), CCl(3)(+) and CCl(2)F(+) cations are unreactive under the experimental conditions used, all other species react via halide abstraction to give [M - Cl](+) and, to a far lesser extent, [M - F](+). In addition, CX(2)(+) ions form CClX(2)(+) in a process which formally amounts to chlorine atom abstraction, but more likely involves chloride ion abstraction followed by charge transfer. CX(+) ions also form minor amounts of CX(3)(+) product ions, possibly via chloride abstraction followed by or concerted with dihalocarbene elimination from the (incipient) [M - Cl](+) ion. Trivalent carbenium ions are less reactive than divalent species, which in turn are less reactive than the monovalent ions (reaction efficiencies are given in parentheses): CF(3)(+)(0.70) < CF(2)(+)(0.78) < CF(+)(0.96). More interestingly, within each family of ions reactivity increases with the number of fluorine substituents (e.g. CF(2)(+) > CFCl(+) > CCl(2)(+) and CF(+) > CCl(+)), i.e. reactivity increases with the ion thermochemical stability, as measured by available standard free enthalpies of formation. Evaluation of the energetics involved shows that reactions are largely driven by the stability of the neutrals more than of the ions. Finally, the products observed in the reaction of Cl(+) are attributed to ionization of the neutral via charge transfer and fragmentation.     

Polycarbide nickel clusters containing interstitial Ni(eta2-C2)4 and Ni2(micro-eta2-C2)4 acetylide moieties: mimicking the supersaturated Ni-C solutions preceding the catalytic growth of CNTs with the structures of [HNi25(C2)4(CO)32]3- and [Ni22(C2)4(CO)28Cl]3-

Reaction of [Ni(6)(CO)(12)](2-) with CCl(4) in CH(2)Cl(2) gives the [HNi(25)(C(2))(4)(CO)(32)](3-) and [Ni(22)(C(2))(4)(CO)(28)Cl](3-) carbonyl clusters containing interstitial Ni(eta(2)-C(2))(4) and Ni(2)(micro-eta(2)-C(2))(4) acetylide moieties.     

Tetraarylpentaborates, [B(5)O(6)Ar(4)](-) (Ar = C(6)H(4)OMe-4, C(6)H(3)Me(2)-2,6): their formation from the reaction of arylboronic acids with an aryloxorhodium complex,structure, and chemical properties

The reactions of (4-methoxyphenyl)boronic acid (1a) and of (2,6-dimethylphenyl)boronic acid (1b) with (PMe(3))(3)Rh-(OC(6)H(4)Me-4) (2) in a 5:1 molar ratio result in the formation of cationic rhodium complexes with new tetraarylpentaborates [Rh(PMe(3))(4)](+)[B(5)O(6)Ar(4)](-) (3a, Ar = C(6)H(4)OMe-4; 3b, Ar = C(6)H(3)Me(2)-2,6). The characterization of 3a is as follows: orthorhombic space group P2(1)2(1)2(1), a = 14.7600(5) A, b = 17.1675(5) A, c = 19.8654(5) A; V = 5033.7(3) A(3); Z = 4. The characterization of 3b is as follows: orthorhombic space group Pnma, a = 23.704(6) A, b = 17.254(8) A, c = 13.304(2) A; V = 5441(2) A(3); Z = 4. An intermediate complex, [Rh(PMe(3))(4)](+)[Ph(3)B(3)O(3)(OC(6)H(4)Me-4)](-) (4), was isolated from the reaction of phenylboroxine, (PhBO)(3), with 2. The tetraarylpentaborates smoothly undergo hydrolysis to give [Rh(PMe(3))(4)](+)[B(5)O(6)(OH)(4)](-) (5).     

Preparation and characterization of the argentates: [Ag[P(CF(3))(2)](2)](-), [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-) (M = Cr, W), and [Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)](-): X-ray crystal structure of [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)

The first example of a mononuclear diphosphanidoargentate, bis[bis(trifluoromethyl)phosphanido]argentate, [Ag[P(CF(3))(2)](2)](-), is obtained via the reaction of HP(CF(3))(2) with [Ag(CN)(2)](-) and isolated as its [K(18-crown-6)] salt. When the cyclic phosphane (PCF(3))(4) is reacted with a slight excess of [K(18-crown-6)][Ag[P(CF(3))(2)](2)], selective insertion of one PCF(3) unit into each silver phosphorus bond is observed, which on the basis of NMR spectroscopic evidence suggests the [Ag[P(CF(3))P(CF(3))(2)](2)](-) ion. On treatment of the phosphane complexes [M(CO)(5)PH(CF(3))(2)] (M = Cr, W) with [K(18-crown-6)][Ag(CN)(2)], the analogous trinuclear argentates, [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-), are formed. The chromium compound [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)] crystallizes in a noncentrosymmetric space group Fdd2 (No. 43), a = 2970.2(6) pm, b = 1584.5(3) pm, c = 1787.0(4), V = 8.410(3) nm(3), Z = 8. The C(2) symmetric anion, [Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)](-), shows a nearly linear arrangement of the P-Ag-P unit. Although the bis(pentafluorophenyl)phosphanido compound [Ag[P(C(6)F(5))(2)](2)](-) has not been obtained so far, the synthesis of its trinuclear counterpart, [K(18-crown-6)][Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)], was successful.     

The structure and chemistry of tris(pentafluorophenyl)borane protected mononuclear nitridotitanium complexes

Treatment of TiCl(NMe(2))(3) with H(3)N·B(C(6)F(5))(3) results in N-H activation and ligand exchange to yield the structurally characterised salt [TiCl(NMe(2))(2)(NMe(2)H)(2)](+)[Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-). Cation exchange with [Me(4)N]Cl, [Ph(4)P]Cl and [(PhCH(2))Ph(3)P]Cl yields the respective ammonium and phosphonium salts of the [Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-) anion. X-ray crystallography reveals that the essential trigonal bipyramidal geometry and composition of the anion is retained in each of these salts despite some minor variations in the Ti-N-B angle and the nature of the interionic interactions. Electronic investigation by DFT calculations confirmed the Ti-N triple bond character implied by the experimentally determined bond length, with the HOMO and HOMO-1 having Ti-N π-bonding character. The dimethylamine ligands of the anion resist substitution by moderate bases but can be displaced by pyridine to give a pentacoordinate anion. In contrast, addition of 2,2'-bipyridyl gives a neutral octahedral complex. Treatment of the pyridine complex with TlCp results in the formation of a four coordinate anionic cyclopentadienyl complex.     

Synthesis and stability of reactive salts of dodecafluoro-closo-dodecaborate(2-)

The synthesis and characterization of several salts of the B(12)F(12)(2-) anion are reported. The potassium salt was prepared in 72% recrystallized yield by treating K(2)B(12)H(12) with liquid HF at 70 degrees C for 14 h and 20% F(2)/N(2) in liquid HF at 25 degrees C for 72 h. The CPh(3)(+), N(n-Bu)(4)(+), NH(n-C(12)H(25))(3)(+), NH(4)(+), and Li(+) salts were prepared by metathesis reactions. The [NH(n-C(12)H(25))(3)](2)[B(12)F(12)] salt is soluble in aromatic hydrocarbon solvents. The B(12)F(12)(2-) anion is remarkably stable. The salts Li(2)B(12)F(12) and [NH(4)](2)[B(12)F(12)] were stable when heated to 450 and 480 degrees C, respectively. The B(12)F(12)(2-) anion did not react with 98% H(2)SO(4), 70% HNO(3), 3 M KOH, a 10-fold excess of Ce(NH(4))(2)(NO(3))(6) in aqueous solution, or metallic sodium in THF. In addition, B(12)F(12)(2-) did not react with metallic lithium in a mixture of ethylene carbonate and dimethyl carbonate, was not reduced at 0 V versus Li(+/0) in that solvent, and underwent a quasi-reversible oxidation at 4.9 V versus Li(+/0). The structure of [CPh(3)](2)[B(12)F(12)] was determined by single-crystal X-ray diffraction: tetragonal, space group I4(1)/acd, a = 19.102(2), b = 19.102(2), c = 20.535(3) A, V = 7492.2(2) A(3), Z = 8, T = 173(2) K, R(1) = 0.064. The B(12)F(12)(2-) anion weakly interacts with the two symmetry related CPh(3)(+) cations via F.C contacts of 3.087(2) A, which are very close to the 3.17 A sum of van der Waals radii for these two atoms. Taken together, the data suggest that B(12)F(12)(2-) may be useful as a very robust weakly coordinating anion.     

Tetrachloro- and Tetrabromostibonium(V) Cations: Raman and (19)F, (121)Sb, and (123)Sb NMR Spectroscopic Characterization and X-ray Crystal Structures of SbCl(4)(+)Sb(OTeF(5))(6)(-) and SbBr(4)(+)Sb(OTeF(5))(6)(-)

The stable salts, SbCl(4)(+)Sb(OTeF(5))(6)(-) and SbBr(4)(+)Sb(OTeF(5))(6)(-), have been prepared by oxidation of Sb(OTeF(5))(3) with Cl(2) and Br(2), respectively. The SbBr(4)(+) cation is reported for the first time and is only the second example of a tetrahalostibonium(V) cation. The SbCl(4)(+) cation had been previously characterized as the Sb(2)F(11)(-), Sb(2)Cl(2)F(9)(-), and Sb(2)Cl(0.5)F(10.5)(-) salts. Both Sb(OTeF(5))(6)(-) salts have been characterized in the solid state by low-temperature Raman spectroscopy and X-ray crystallography. Owing to the weakly coordinating nature of the Sb(OTeF(5))(6)(-) anion, both salts are readily soluble in SO(2)ClF and have been characterized in solution by (121)Sb, (123)Sb, and (19)F NMR spectroscopy. The tetrahedral environments around the Sb atoms of the cations result in low electric field gradients at the quadrupolar (121)Sb and (123)Sb nuclei and correspondingly long relaxation times, allowing the first solution NMR characterization of a tetrahalocation of the heavy pnicogens. The following crystal structures are reported: SbCl(4)(+)Sb(OTeF(5))(6)(-), trigonal system, space group P&thremacr;, a = 10.022(1) ?, c = 18.995(4) ?, V = 1652.3(6) ?(3), D(calc) = 3.652 g cm(-)(3), Z = 2, R(1) = 0.0461; SbBr(4)(+)Sb(OTeF(5))(6)(-), trigonal system, space group P&thremacr;, a = 10.206(1) ?, c = 19.297(3) ?, V = 1740.9(5) ?(3), D(calc) = 3.806 g cm(-)(3), Z = 2, R(1) = 0.0425. The crystal structures of both Sb(OTeF(5))(6)(-) salts are similar and reveal considerably weaker interactions between anion and cation than in previously known SbCl(4)(+) salts. Both cations are undistorted tetrahedra with bond lengths of 2.221(3) ? for SbCl(4)(+) and 2.385(2) ? for SbBr(4)(+). The Raman spectra are consistent with undistorted SbX(4)(+) tetrahedra and have been assigned under T(d)() point symmetry. Trends within groups 15 and 17 are noted among the general valence force constants of the PI(4)(+), AsF(4)(+), AsBr(4)(+), AsI(4)(+), SbCl(4)(+) and SbBr(4)(+) cations, which have been calculated for the first time, and the previously determined force constants for NF(4)(+), NCl(4)(+), PF(4)(+), PCl(4)(+), PBr(4)(+), and AsCl(4)(+), which have been recalculated for the P and As cations in the present study. The SbCl(4)(+) salt is stable in SO(2)ClF solution, whereas the SbBr(4)(+) salt decomposes slowly in SO(2)ClF at room temperature and rapidly in the presence of Br(-) ion and in CH(3)CN solution at low temperatures. The major products of the decompositions are SbBr(2)(+)Sb(OTeF(5))(6)(-), as an adduct with CH(3)CN in CH(3)CN solvent, and Br(2).