Phospha-s-triazines II. Mass spectra of mono(diarylphospha)-s-triazines

Electron impact fragmentation patterns were obtained for 1-dephenylphospha-3,5-bis(perfluoro-n-heptyl)-2,4,6-triazine, 1-diphenylphospha-3,5-bis[C₃F₇(OCF(CF₃)CF₂)_xOCF(CF₃]-2,4,6-triazine (x=1 and 2) and their pentafluorophenyl analogues. In each instance the ion R₂PN₂C⁺ (RC₆H₅ or C₆F₅) constituted the base peak. Based on the observed metastable peaks, fragmentation pathways leading to the formation of this and other significant ions are postulated and similarities to s-triazine and diphenyl phosphazene trimer breakdown patterns are discussed.     

Phospha-s-triazines. I. Syntheses and properties of mono(diarylphospha)-s-triazines

A series of monophospha-s-triazines, namely l-diphenylphospha-3,5-bis(perfluoro-n-heptyl)-2,4,6-triazine, 1-diphenylphospha-3,5-bis[C₃F₇-[OCF(CF₃)CF₂]_xOCF(CF₃)]-2,4,6-triazine (x = 1 and 2), and the penta-fluorophenyl-substituted analogues were prepared, in yields of 50-75%, from the respective imidoylamidines and trichlorophosphoranes. The physical properties of the corresponding phenyl and pentafluorophenyl monophospha-s-triazines did not differ significantly; the perfluoroalkyl-substituted materials were low melting solids whereas the perfluoroalkyl-ether-containing compositions were liquids. Preliminary degradative studies showed these compounds to be thermally and oxidatively stable. The l-diphenylphospha-3,5-bis[C₃F₇OCF(CF₃)CF₂OCF(CF₃)]-2,4,6-triazine was found to be an effective anti-corrosion additive for perfluoroalkylether type fluids.     

D–π–A Triarylboron Compounds with Tunable Push–Pull Character Achieved by Modification of Both the Donor and Acceptor Moieties

The push–pull character of a series of donor–bithienyl–acceptor compounds has been tuned by adopting triphenylamine or 1,1,7,7‐tetramethyljulolidine as a donor and B(2,6‐Me₂‐4‐RC₆H₂)₂ (R=Me, C₆F₅ or 3,5‐(CF₃)₂C₆H₃) or B[2,4,6‐(CF₃)₃C₆H₂]₂ as an acceptor. Ir‐catalyzed C?H borylation was utilized in the derivatization of the boryl acceptors and the tetramethyljulolidine donor. The donor and acceptor strengths were evaluated by electrochemical and photophysical measurements. In solution, the compound with the strongest acceptor, B[2,4,6‐(CF₃)₃C₆H₂]₂ ((FMes)₂B), has strongly quenched emission, while all other compounds show efficient green to red (Φ_F=0.80–1.00) or near‐IR (NIR; Φ_F=0.27–0.48) emission, depending on solvent. Notably, this study presents the first examples of efficient NIR emission from three‐coordinate boron compounds. Efficient solid‐state red emission was observed for some derivatives, and interesting aggregation‐induced emission of the (FMes)₂B‐containing compound was studied. Moreover, each compound showed a strong and clearly visible response to fluoride addition, with either a large emission‐color change or turn‐on fluorescence.     

Heavy Carbene Analogues: Donor‐Free Bismuthenium and Stibenium Ions

Kinetically stabilized congeners of carbenes, R₂C, possessing six valence electrons (four bonding electrons and two non‐bonding electrons) have been restricted to Group 14 elements, R₂E (E=Si, Ge, Sn, Pb; R=alkyl or aryl) whereas isoelectronic Group 15 cations, divalent species of type [R₂E]⁺ (E=P, As, Sb, Bi; R=alkyl or aryl), were unknown. Herein, we report the first two examples, namely the bismuthenium ion [(2,6‐Mes₂C₆H₃)₂Bi][BAr^F₄] ( 1 ; Mes=2,4,6‐Me₃C₆H₂, Ar^F=3,5‐(CF₃)₂C₆H₃) and the stibenium ion [(2,6‐Mes₂C₆H₃)₂Sb][B(C₆F₅)₄] ( 2 ), which were obtained by using a combination of bulky meta‐terphenyl substituents and weakly coordinating anions.     

Selective deoxygenation of gibberellic acid with fluoroarylborane catalysts

Reductive late-stage functionalization of gibberellic acid is reported using three fluoroarylborane Lewis acids; (B(C₆F₅)₃, B(3,5-C₆H₃(CF₃)₂), and B(2,4,6-C₆H₂F₃)₃) in combination with a tertiary silane and a borane (HBCat) reductant. In each case, C–O bond activation occurs, and different products are obtained depending on the reductant and catalyst employed.     

Synthesis,Structure, and Lanthanide Derivatives of an Unusual Hexameric Alcohol: [2,4,6-(CF3)3C6H2CH2OH]6

Hitherto unknown 2,4,6-tris(trifluoromethyl)benzyl alcohol ( 3 ) was synthesized in 41 % yield by treatment of freshly prepared R_FLi ( 2 ) with paraformaldehyde (R_F = 2,4,6-tris(trifluoromethyl)phenyl). According to an X-ray diffraction study the crystal structure of 3 consists of S₆ symmetric cyclic hexamers [2,4,6-(CF₃)₃C₆H₂CH₂OH]₆. Deprotonation of 3 with NaN(SiMe₃)₂ in toluene afforded the unsolvated sodium alkoxide derivative R_FCH₂ONa ( 4 ). Homoleptic lanthanide alkoxides of the type Ln(OCH₂R_F)₃ (Ln = Nd ( 5 ), Sm ( 6 ), Yb ( 7 )) were made by treatment of Ln(C₅H₅)₃ with three equivalents of 3 . Similar reactions in a 1:1 molar ratio afforded the bis(cyclopentadienyl)lanthanide alkoxide derivatives (C₅H₅)₂Ln(OCH₂R_F) (Ln = Nd ( 8 ), Sm ( 9 ), Yb ( 10 )).     

Halogen Complexes of Anionic N-Heterocyclic Carbenes

The lithium complexes [(WCA-NHC)Li(toluene)] of anionic N-heterocyclic carbenes with a weakly coordinating anionic borate moiety (WCA-NHC) reacted with iodine, bromine, or CCl₄ to afford the zwitterionic 2-halogenoimidazolium borates (WCA-NHC)X (X=I, Br, Cl; WCA=B(C₆F₅)₃, B{3,5-C₆H₃(CF₃)₂}₃; NHC=IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, or NHC=IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). The iodine derivative (WCA-IDipp)I (WCA=B(C₆F₅)₃) formed several complexes of the type (WCA-IDipp)I ⋅ L (L=C₆H₅Cl, C₆H₅Me, CH₃CN, THF, ONMe₃), revealing its ability to act as an efficient halogen bond donor, which was also exploited for the preparation of hypervalent bis(carbene)iodine(I) complexes of the type [(WCA-IDipp)I(NHC)] and [PPh₄][(WCA-IDipp)I(WCA-NHC)] (NHC=IDipp, IMes). The corresponding bromine complex [PPh₄][(WCA-IDipp)₂Br] was isolated as a rare example of a hypervalent (10-Br-2) system. DFT calculations reveal that London dispersion contributes significantly to the stability of the bis(carbene)halogen(I) complexes, and the bonding was further analyzed by quantum theory of atoms in molecules (QTAIM) analysis.     

Positional disorder manifested as compositional in a pseudo‐C2‐symmetrical Pd complex

The title compound {2‐[3,5‐bis(trifluoromethyl)‐1H‐pyrazol‐1‐ylmethyl]‐6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐ylmethyl)pyridine}methylpalladium(II) tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate, [Pd(C₁₈H₁₈F₆N₅)][B(C₈H₃F₆)₄], crystallizes as discrete cations and anions. The cation possesses a pseudo‐twofold axis about which positional disorder of the tridentate ligand is exhibited. The four substituents on the two pyrazole rings exhibit CH₃/CF₃ disorder, while all other atoms are ordered. Thus, this disorder can be conveniently described `locally' as compositional, while `globally' for the entire tridentate ligand it is positional. The anion also exhibits typical rotational positional disorder in three of the CF₃ groups. All disordered CF₃ groups were modeled with idealized C_3v geometry.     

Fluoroborates by Cleavage of Trimethylamine‐bis(trifluoromethyl)boranes with NEt3 × 3 HF. Structures of C6F5(CF3)2B · NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF]

Trimethylamine‐bis(trifluoromethyl)boranes R(CF₃)₂B · NMe₃ (R = cis/trans‐CF₃CF=CF ( 1/2 ), HC≡C ( 3 ), H₂C=CH ( 4 ), C₂H₅ ( 5 ), C₆H₅CH₂ ( 6 ), C₆F₅ ( 7 ), C₆H₅ ( 8 )) react with NEt₃ × 3 HF depending on the nature of R at 155–200 °C under replacement of the trimethylamine ligand to form the corresponding fluoro‐bis(trifluoromethyl)borates [R(CF₃)₂BF]^– ( 1 a/2 a – 8 a ). The structures of 7 , K[C₆H₅CH₂(CF₃)₂BF] ( K‐6 a ), and K[C₆H₅(CF₃)₂BF] ( K‐8 a ) have been investigated by single‐crystal X‐ray diffraction. In 7 the CF₃ groups make short repulsive contacts with NMe₃ and C₆F₅ entities – the B–CF₃ bonds being unusually long. The B–F bond lengths of K‐6 a and K‐8 a (1.446(3) and 1.452(2) Å, respectively) are long for a fluoroborate.     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

Unique catalytic behavior of chromium complexes having halogenated bis(imino)pyridine ligands for ethylene polymerization

Reactions of CrCl₃(thf)₃ with bis(imino)pyridines gave a series of {bis(imino)pyridine}chromium(III) trichloride complexes, {2,6‐(RN?CMe)₂C₅H₃N}CrCl₃ [R = C₆HPr₂‐2,6 ( 1 ), C₆H₃Et₂‐2,6 ( 2 ), C₆H₃Me₂‐2,6 ( 3 ), C₆H₂Me₃‐2,4,6 ( 4 ), C₆H₃Me₂‐3,5 ( 5 ), C₆H₅ ( 6 ), cyclohexyl ( 7 ), 2‐methyl‐1‐naphthyl ( 8 ), C₆H₃F₂‐2,6 ( 9 ), C₆H₃Br₂‐2,6 ( 10 ), C₆F₅ ( 11 )]. Pseudo‐octahedral geometries of 6 , 10 , and 11 were revealed by X‐ray crystallography. The complexes having bulky substituents such as 1 – 4 showed high activity for ethylene polymerization in combination with modified methylaluminoxane (MMAO) to give linear polyethylenes. In sharp contrast, the pentafluorophenyl complex 11 /modified methylaluminoxane system was found to be moderately active for ethylene homopolymerization to give moderately branched polyethylene with only ethyl branches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3368–3375, 2005     

Fluorocarbon derivatives of nitrogen. Part 14. Studies on some (CF3)2 no-substituted fluoroaromatics; thermal rearrangement of 4-[bis(trifluoromethyl)amino-oxy]tetrafluoropyridine

The sodium salt (CF₃)₂ NO⁻Na⁺ (I) [from (CF₃)₂NOH + NaH in Et₂O], is an alternative bis(trifluoromethyl)amino-oxylating agent to the adduct (CF₃)₂NOH.CsF (III). With pentafluoropyridine it affords 4-X.C₅F₄N (II) + 2,4-X₂.C₅F₃N (IV), [X = (CF₃)₂NO]. It has been used to obtain a number of new bis(trifluoromethyl)amino-oxy-compounds; $\text{i.e.}$ the following conversions have been effected: perfluoro-(4-isopropylpyridine)→ 2-X.C₅F₃N.CF(CF₃)₂-4 (V) + 2,6-X₂.C₅F₂N.CF(CF₃)₂-4 (VI); 3-chlorotetrafluoropyridine → 4-X.C₅F₃N.Cl-3 (VII) and 2-X.C₅F₃N.Cl-5 (VIII) (not separated) + 2,4-X₂.C₅F₂N.Cl-5 (IX), 3,5-dichlorotrifluoropyridine → 2- (XI) and 4-X.C₅F₂N.Cl₂-3,5 (X) (not separated) + 2,4-X₂.C₅FN.Cl₂-3,5 (XII); and perfluorotoluene → 4-X.C₆F₄.CF₃-1 (XIII). Hexafluorobenzene resisted attack by (CF₃)₂NONa under the conditions used with these aromatic substrates ($\text{ca}$ 20 °C). Static pyrolysis (125 °C) of 4-[bis(trifluoromethyl)amino-oxy]tetrafluoropyridine (II) gave a mixture of 6-bis(trifluoromethyl)amino]tetrafluoro-4-azacyclohexa-2, 4-dienone (XV) and 4-[bis(trifluoromethyl)amino]tetrafluoro-4-azacyclohexa-2,5-dienone (XVI). The ¹³C chemical shifts, assigned by analysis of ¹⁹F-coupled and ¹⁹F broad-band decoupled ¹³C n.m.r. spectra, are in accord with a +M effect similar to that of fluorine for a (CF₃)₂NO- substituent in the 2- and 4- positions of a polyfluoropyridine and a slightly smaller -I effect; the steric effect of (CF₃)₂NO on the shifts is less than that of chlorine. In contrast, a ring carbon carrying a (CF₃)₂CF- substituent is markedly shielded compared with one carrying fluorine, presumably by a steric effect.     

Autoinduced Catalysis and Inverse Equilibrium Isotope Effect in the Frustrated Lewis Pair Catalyzed Hydrogenation of Imines

The frustrated Lewis pair (FLP)‐catalyzed hydrogenation and deuteration of N‐benzylidene‐tert‐butylamine ( 2 ) was kinetically investigated by using the three boranes B(C₆F₅)₃ ( 1 ), B(2,4,6‐F₃‐C₆H₂)₃ ( 4 ), and B(2,6‐F₂‐C₆H₃)₃ ( 5 ) and the free activation energies for the H₂ activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol^?1) for the H₂ activation by the imine compared to the amine. Surprisingly, the imine reduction using D₂ proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.     

Linkage Isomerism Leading to Contrasting Carboboration Chemistry: Access to Three Constitutional Isomers of a Borylated Phosphaalkene

We describe the reactivity of two linkage isomers of a boryl-phosphaethynolate, [B]OCP and [B]PCO (where [B]=N,N’-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl), towards tris- (pentafluorophenyl)borane (BCF). These reactions afforded three constitutional isomers all of which contain a phosphaalkene core. [B]OCP reacts with BCF through a 1,2 carboboration reaction to afford a novel phosphaalkene, E-[B]O{(C₆F₅)₂B}C=P(C₆F₅), which subsequently undergoes a rearrangement process involving migration of both the boryloxy and pentafluorophenyl substituents to afford Z-{(C₆F₅)₂B}(C₆F₅)C=PO[B]. By contrast, [B]PCO undergoes a 1,3-carboboration process accompanied by migration of the N,N’-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl to the carbon centre.     

The Direct Synthesis of Arylxenon Trifluoromethanesulfonates via electrophilic substitution

The reaction of xenonbis(trifluoroacetate) and trifluoromethanesulfonic acid (triflic acid) gave the new, highly reactive unsymmetrical xenon-oxo species CF₃COOXeOSO₂CF₃. Benzene derivates, containing electron withdrawing substituents such as -F, -CF₃, -Cl or -NO₂ were electrophilic attacked by this intermediate to yield arylxenon trifluoromethanesulfonates. Via this one-pot synthesis trifluoromethanesulfonates with the cations [Xe(2,4,6-F₃C₆H₂)]⁺, [Xe(2-F-5-NO₂C₆H₃)]⁺, [Xe(2-F-5-CF₃C₆H₃)]⁺ and [Xe(3,5-(CF₃)₂C₆H₃)]⁺ were prepared. All compounds were characterized by their NMR, mass, and vibrational spectra. Additionally, several new arylxenon trifluoromethanesulfonates were detected by ¹²⁹Xe-NMR spectroscopy as products of the reaction of 1,3-F₂C₆H₄ and further deactivated benzenes with xenontrifluoroacetate trifluoromethane sulfonate. Fluoro substituents in ortho position to xenon significantly increase the thermal stability of the arylxenon trifluoromethanesulfonates obtained. The molecular structure of [Xe(2,6-F₂C₆H₃)][OSO₂CF₃] was determined by single crystal diffraction methods. The arylxenon unit is weakly coordinated by one oxygen atom of the CF₃SO₃ anion. The salt crystallizes in the triclinic space group P1 , a = 880.9(3) pm, b = 1093.9(5) pm, c = 1209.8(5) pm, α = 89.04(4)°, β = 74.23(3)°, γ = 86.03(3)°, Z = 4.     

C6F5XeF, a versatile starting material in xenon-carbon chemistry

The molecules Ar_FXeF (Ar_F=C₆F₅, 2,4,6-C₆H₂F₃) with a more polar Xe-F bond than XeF₂ are versatile starting materials for substitution reactions. Fluorine-aryl substitutions with Cd(Ar_F)₂, C₆F₅SiMe₃/[F]⁻, and C₆F₅SiF₃ formed symmetric and/or asymmetric diarylxenon compounds. Applying C₆F₅BF₂, with a higher F⁻-affinity than the corresponding aryltrifluorosilane, in contrast gave the salt [RXe] [Ar_FBF₃]. Using the alkenyl and alkyl compounds CF₂=CFSiMe₃/[F]⁻, CF₃SiMe₃/[F]⁻, and Cd(CF₃)₂ in reactions with C₆F₅XeF, the perfluoroalkenyl or -alkyl transfer reagents were consumed without observing C₆F₅XeCF=CF₂ or C₆F₅XeCF₃ but the formation of Xe(C₆F₅)₂ (dismutation product) and in the latter case C₆F₅CF₃ (coupling product), gave hints of the desired intermediates.     

Homolytic C−H Bond Activation by Phosphine−Quinone-Based Radical Ion Pairs

Herein, we present the formation of transient radical ion pairs (RIPs) by single-electron transfer (SET) in phosphine−quinone systems and explore their potential for the activation of C−H bonds. PMes₃ (Mes=2,4,6-Me₃C₆H₂) reacts with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) with formation of the P−O bonded zwitterionic adduct Mes₃P−DDQ ( 1 ), while the reaction with the sterically more crowded PTip₃ (Tip=2,4,6-iPr₃C₆H₂) afforded C−H bond activation product Tip₂P(H)(2-[CMe₂(DDQ)]-4,6-iPr₂-C₆H₂) ( 2 ). UV/Vis and EPR spectroscopic studies showed that the latter reaction proceeds via initial SET, forming RIP [PTip₃]⋅⁺[DDQ]⋅⁻, and subsequent homolytic C−H bond activation, which was supported by DFT calculations. The isolation of analogous products, Tip₂P(H)(2-[CMe₂{TCQ−B(C₆F₅)₃}]-4,6-iPr₂-C₆H₂) ( 4 , TCQ=tetrachloro-1,4-benzoquinone) and Tip₂P(H)(2-[CMe₂{oQ^tBu−B(C₆F₅)₃}]-4,6-iPr₂-C₆H₂) ( 8 , oQ^tBu=3,5-di-tert-butyl-1,2-benzoquinone), from reactions of PTip₃ with Lewis-acid activated quinones, TCQ−B(C₆F₅)₃ and oQ^tBu−B(C₆F₅)₃, respectively, further supports the proposed radical mechanism. As such, this study presents key mechanistic insights into the homolytic C−H bond activation by the synergistic action of radical ion pairs.     

Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines,RnC6H5−nNH2 Leading to New Diamines,Triamines, Imines,or 1,3,5-Triazines Dependent upon Substituent R

The reactions of the Mannich reagent Et₃SiOCH₂NMe₂ ( 1 ) with a variety of anilines (mono-substituted RC₆H₄NH₂, R=H, 4-CN, 4-NO₂, 4-Ph, 4-Me, 4-MeO, 4-Me₂N; di-substituted R₂C₆H₃NH₂, R₂=3,5-(CH₃)₂, 3,5-(CF₃)₂; tri-substituted R₃C₆H₂NH₂, R₃=3,5-Me₂-4-Br and a “super bulky” aniline (Ar*NH₂) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC₆H₄NH(CH₂NMe₂) [R=CN ( 2 a ), NO₂ ( 2 b )] and R₂C₆H₃NH(CH₂NMe₂) [R₂=3,5-(CF₃)₂ ( 2 c) ] were formed. Further reaction of 2 a , b , c with 1 yielded the corresponding triamines RC₆H₄N(CH₂NMe₂)₂ (R=CN ( 3 a ), NO₂ ( 3 b ) and R₂C₆H₃N(CH₂NMe₂)₂, R₂=3,5-(CF₃)₂ ( 3 c ). The new polyamines were characterized by NMR spectroscopy, and for 2 a , 2 c _, and 3 c , by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe₂, 4-Me, 3,5-Me₂, 3,5-Me₂-4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO ( 5 a ), 4-Me₂N ( 5 b ), 4-Me ( 5 c ), 3,5-Me₂ ( 5 d ), 3,5-Me₂-4-Br ( 5 e ), 4-Ph ( 5 f ), 4-Cl ( 5 g ). The “super bulky” aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH₂ ( 4 ) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of “Silick” chemistry.     

Accessing Cationic α-Silylated and α-Germylated Phosphorus Ylides

The synthesis and full characterization of α-silylated (α-SiCPs; 1 – 7 ) and α-germylated (α-GeCPs; 11 – 13 ) phosphorus ylides bearing one chloride substituent R₃PC(R¹)E(Cl)R²₂ (R=Ph; R¹=Me, Et, Ph; R²=Me, Et, iPr, Mes; E=Si, Ge) is presented. The molecular structures were determined by X-ray diffraction studies. The title compounds were applied in halide abstraction studies in order to access cationic species. The reaction of Ph₃PC(Me)Si(Cl)Me₂ ( 1 ) with Na[B(C₆F₅)₄] furnished the dimeric phosphonium-like dication [Ph₃PC(Me)SiMe₂]₂[B(C₆F₅)₄]₂ ( 8 ). The highly reactive, mesityl- or iPr-substituted cationic species [Ph₃PC(Me)SiMes₂][B(C₆F₅)₄] ( 9 ) and [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) could be characterized by NMR spectroscopy. Carrying out the halide abstraction reaction in the sterically demanding ether iPr₂O afforded the protonated α-SiCP [Ph₃PCH(Et)Si(Cl)iPr₂][B(C₆F₅)₄] ( 6 dec ) by sodium-mediated basic ether decomposition, whereas successfully synthesized [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) readily cleaves the F−C bond in fluorobenzene. Thus, the ambiphilic character of α-SiCPs is clearly demonstrated. The less reactive germanium analogue [Ph₃PC(Me)GeMes₂][B{3,5-(CF₃)₂C₆H₃}₄] ( 14 ) was obtained by treating 11 with Na[B{3,5-(CF₃)₂C₆H₃}₄] and fully characterized including by X-ray diffraction analysis. Structural parameters indicate a strong C_Ylide−Ge interaction with high double bond character, and consequently the C−E (E=Si, Ge) bonds in 9 , 10 and 14 were analyzed with NBO and AIM methods.     

Arylvanadin(III)-Verbindungen,III. Darstellung und Eigenschaften von Triarylvanadin-Verbindungen

Arylvanadium(III) Compounds. III. Preparation and Properties of Triaryl Vanadium Complexes The synthesis of triarylvanadium compounds, VR₃ (R = C₆H₅; 2,6-(CH₃)₂C₆H₃; 2,4,6-(CH₃)₃C₆H₂; (CH₃)₅C₆) is investigated. Only the compounds V[2,6-(CH₃)₂C₆H₃]₃ and V[2,4,6-(CH₃)₃C₆H₂]₃ (crystallized with tetrahydrofuran) are obtained. The complexes V(C₆H₅)(dipy)₂ · THF, V[2,4,6-(CH₃)₃C₆H₂]₃ · Do (Do = py, dipy) are described too.