Intramolecular nucleophilic substitution in C6F5 moiety. The fluoride-dialkylamino exchange in decafluorodiphenlamino moiety

The reactions of [In(NEt₂)₃]₂ and Sb(NEt₂)₃ with an equimolar amount of decafluorodiphenylamine (DFDPA, LH) lead to the indium or antimony amides [(C₆F₅)₂NIn(NEt₂)₂]₂ (1) and (C₆F₅)₂NSb(NEt₂)₂ (2). Compound 2 rearranged further to give monofluoride Et₂NSb(F)[N(o-Et₂N-C₆F₄)(C₆F₅)] (3) and then difluoride F₂Sb[N(o-Et₂N-C₆F₄)₂] (4). The hydrolysis of 4 gave free ligand HN(o-Et₂N-C₆F₄)₂ (5). Closely related HN(o-Me₂N-C₆F₄)₂ (6) was prepared from the reaction of Bi(NMe₂)₃ with DFDPA. The reactions of LiN(C₆F₅)₂·THF with metal halides gave Sb[N(C₆F₅)₂]₃ (7), Me₃Sb(Br)[N(C₆F₅)₂] (8), Me₃Sb(Cl)[N(C₆F₅)₂] (9), Me₃Sb[N(C₆F₅)₂]₂ (10), [Li(THF)₂][In{N(C₆F₅)₂}₃Cl] (11). The X-ray structural investigations of 2 and 8 are presented.     

Structural investigations on new iron-acyl derivatives of B(C6F5)3

Reactions between [Fe(η-C₅H₅)(MeCO)(CO)(L)], L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy₃ (4), CO (5), and B(C₆F₅)₃ give new complexes [Fe(η-C₅H₅){MeCOB(C₆F₅)₃}(CO)(L)] L = PPh₃ (7), PMe₃ (8), PPhMe₂ (9), PCy₃ (10), CO (11), where B(C₆F₅)₃ coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C₅H₅){HOB(C₆F₅)₃}(CO)(PPh₃)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C-O bond thus π populations cannot be inferred from the distance changes.     

X-ray crystal structures and solution dynamics of sodium organofluorotitanates [Na{Ti2(C5Me5)2F7}] and [NaTi6(C5Me5)5F20(H2O)]·(THF)

[Na{Ti₂(C₅Me₅)₂F₇}] (1) was prepared from sodium fluoride and [{Ti(C₅Me₅)F₃}₂] [H.W. Roesky, et al., Angew. Chem. Int. Ed. Engl. 31 (1992) 864-866]. The solid-state 1 consists of a polymeric chain of two rows of dititanate anions [Ti₂(C₅Me₅)₂F₇]⁻ connected by sodium ions in the middle of the chain. Each sodium ion is coordinated by five fluorine atoms from three [Ti₂(C₅Me₅)₂F₇]⁻ anions. The variable-temperature ¹⁹F NMR of CD₃CN solution of 1 revealed interconversions of monomeric species [Na(CD₃CN)_n{Ti₂(C₅Me₅)₂F₇}] (1solv) with different number of CD₃CN ligands on the sodium ion. The addition of HMPA to the CD₃CN solution of 1 allows ¹⁹F NMR observation of 1·HMPA (1a) and 1·HMPA·CD₃CN (1b) in the slow exchange. The solid-state structure of [NaTi₆(C₅Me₅)₅F₂₀(H₂O)]·(THF) (2·THF) reveals the sodium ion coordinated by four fluorine atoms from the anion [Ti₂(C₅Me₅)₂F₇]⁻ and by three fluorine atoms from the cluster [Ti₄(C₅Me₅)₃F₁₃(H₂O)].     

Complex formation between water-soluble sulfonated calixarenes and C60 fullerene

The inclusion complexes of sulfonated thiacalix[4]arene 1 and calix[6]arene 2 sodium salts with C₆₀ fullerene were investigated by photoluminescence (PL) and quantum-chemical methods. The stoichiometries of calixarene/C₆₀ complexes were found to be 2:1 for 1 and 1:1 for 2. Related quantum-chemical investigations show that C₆₀ fullerene is included in a cavity composed of two half-bowl molecules of 1. The C₆₀ fullerene ball is located deep within the cavity of 2 and the negatively charged sulfonate arms probably inhibit the formation of the bowl-shaped capsule that was observed in the case of 1.     

Reactions of bis(alkynyl)silanes with HB(C6F5)2: Formation of boryl-substituted silacyclobutene derivatives

Treatment of R₂Si(CC-SiMe₃)₂ [1a (Me), 1b (Ph)] with HB(C₆F₅)₂ at low temperature (253 K (a), 273 K (b)) gives the -B(C₆F₅)₂ substituted silacyclobutene products (4a,b) under kinetic control. Upon warming to room temperature they disappear to form the thermodynamically favoured isomeric silole derivatives (2a,b). Similar treatment of Me₂Si(CC-R¹)₂ [5a (R¹ = Ph), 5b (R¹ = tert-butyl) with HB(C₆F₅)₂ at room temperature gave the stable -B(C₆F₅)₂ substituted silacyclobutene derivatives 6 and 7, respectively. Subsequent photolysis resulted in a Z- to E-isomerization of the substituted exocyclic CC double bonds in these products. The silacyclobutene derivative E-6 was characterized by an X-ray crystal structure analysis.     

Ab initio investigations of the C2F4S isomers and of their interconversions

The transition states and the activation energies for the unobserved isomerization reactions between the three possible C₂F₄S isomers with divalent sulfur, trifluorothioacetyl fluoride 1, tetrafluorothiirane 2, and trifluoroethenesulfenyl fluoride 3, have been determined by ab initio Hartree-Fock (HF), Møller-Plesset second-order perturbation (MP2) calculations and by Gaussian-3 theory. The results show that the unobserved isomerization reactions are feasible. Furthermore, all three isomers should exist as stable species, but the unknown isomer, 3, is considerably less stable than the known isomers, 1 and 2.     

Synthesis of 4-aziridino[C60]fullerene-1,8-naphthalimide (C60-NI dyads) and their photophysical properties

A series of 4-aziridino[C₆₀]fullerene-1,8-naphthalimide (C₆₀-NI) dyads 4 ([6,6]-closed ring) were synthesized as the only addition product from the reaction of C₆₀ with the corresponding azide compounds 3 under microwave irradiation in good yield. A quenching of fluorescence was shown in dyads 4, and this decay was evidenced to be an intramolecular process.     

Hydrothermal synthesis and characterization of the first 1-D indiumphosphate chain In2(HPO4)2(H2PO4)2F2·C4N2H12, a precursor for high dimensional structures

The first one-dimensional (1-D) indiumphosphate chain, In₂(HPO₄)₂(H₂PO₄)₂F₂·C₄N₂H₁₂ (1), has been hydrothermally prepared using piperazine (PIP) as a template. The structure consists of infinite chains of trans,trans-corners-sharing InO₄F₂ octahedra with the adjacent octahedra being bridged by tetrahedral PO₃(OH) and PO₂(OH)₂ units, which are H-bonded with amine groups of the organic cations. Interestingly, this macroanionic chain InP₂O₈H₃F⁻ is similar to that found in the mineral tancoite-like chains and has potential to further set up higher-dimensional networks. On heating 1 in the presence of additional phosphoric acid at 180 °C under hydrothermal condition, compound 2, In₂(OH)(H₂O)(PO₄)₂·H₃O·H₂O, possessed a 3-D structure building from the repetition of a secondary building unit is obtained. When 1 is heated with additional PIP, an unknown phase, compound 3 is formed. Finally, on treatment with another amine, such as diethylenetriamine or 1,4-diaminobutane, at 180 °C, 1, as a precursor, can convert into a previously known 3-D framework structure with 16-membered ring compound 4. Compounds 1 and 2 are determined by single-crystal X-ray diffraction. Furthermore, 1 is characterized by X-ray powder diffraction, IR spectroscopy, inductively coupled plasma analysis, thermogravimetric analysis and differential thermal analysis.     

Room-temperature long-lived [Nb2F11] salts of radical cations of simple arenes: EPR, UV-Vis and DFT results

The computed structures of the long-lived radical cation salts [Arene][Nb₂F₁₁] [Arene = 1,4-F₂-2,5-(OMe)₂C₆H₂, 2; 1,4-(OMe)₂C₆H₄, 3; 2,5-(OEt)₂(Me)C₆H₃, 4; C₆H₆, 5] and that of the transient [1,3-(OMe)₂C₆H₄][Nb₂F₁₁], 6, obtained for the gas-phase by DFT at the B3LYP/6-31G∗∗ level, are presented. The degree of inertness observed in chloroform solution seems to increase on decreasing the steric demand of the ring substituents, and may be correlated to the calculated distance between the cation-centroid and the niobium atoms. The room-temperature EPR spectra of 2-4, in CHCl₃, are described in detail; the spectrum of 3 is compared to those of analogous 1,4-dimethoxybenzene radical species reported previously. The EPR spectra display a hyperfine structure due to coupling of the unpaired electron with nuclei belonging to both the cation (H and F in the case of 2) and the anion (F and eventually Nb). The UV-Vis spectra of 2-4 exhibit one strong absorption attributed to the cation and one anion-to-cation charge-transfer band (e.g. for 3 at 398 and 589 nm, respectively). Thermodynamic calculations indicate that the low yield formation of the benzene radical salt 5 occurs with Gibbs free energy variation significantly higher than those involved in the synthesis of 2-4 and 6.     

Lycopladines F and G, new C16N2-type alkaloids with an additional C4N unit from Lycopodium complanatum

Two new Lycopodium alkaloids, lycopladines F (1) and G (2), have been isolated from the club moss Lycopodium complanatum, and the structures and relative stereochemistries of 1 and 2 were elucidated on the basis of spectroscopic data. Lycopladine F (1) is a rare C₁₆N₂-type Lycopodium alkaloid possessing an amino acid residue (C₄N).     

Synthesis of C60 derivatives for photoaffinity labeling

In order to study the interaction of fullerenes with biological molecules, a novel photoaffinity labeling agent derived from C₆₀ was designed and synthesized. As photosensitive functional groups, azide group, and aziridine group are utilized. A convenient synthetic route via fulleropyrrolidine 2 was employed to obtain compounds labeling agents 5 and 9.     

Synthesis of fluorinated trithioether compounds: X-ray structures of 1,3,5-(CH2SRf)3-2,4,6-(CH3)3C6, Rf = C6F5, 4-HC6F4, or 2-FC6H4

A series of three new trithioether compounds containing fluorinated phenyl moieties, 1,3,5-(CH₂SR_f)₃-2,4,6-(CH₃)₃C₆, R_f = C₆F₅ (1), 4-HC₆F₄ (2), or 2-FC₆H₄ (3), were prepared by treatment of 1,3,5-(CH₂Br)₃-2,4,6-(CH₃)₃C₆ with the corresponding Pb(SC₆F₅)₂ or NaSR_f. The new structures were verified by elemental analyses, IR, ¹H NMR, ¹⁹F NMR spectroscopies, and mass spectra. The single crystal X-ray diffraction studies of 1-3 show a similar cis,trans,trans-conformation for the three fluorophenylthiomethyl groups attached to the central benzene ring with all dihedral angles between planes of central ring and external rings close to 0°, giving flat molecules. Comparing, 1-3 with closely related tripodal molecules built-up on 2,4,6-trimethylbenzene, arrangement of one SR group respect to others seems to be defined by the nature of the R substituent. Then in the case of 1-3, a parallel arrangement of rings is favored over an orthogonal one, which would bring the ortho-F atoms close to H atoms of the methylene groups.     

Formation of keto-carbeniums from 1,2,2-triarylacenaphthen-1-ols by breaking a long CC bond: unusual alcohol protonolysis accompanied by formal hydride abstraction

Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I₂ induced the C₁C₂ bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b⁺, the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF₄ did not induce the expected COH bond heterolysis but caused fission of COH and C₁C₂ bonds to give exactly the same carbenium 2⁺.     

Synthesis and structural characterization of an unusual heptameric aluminum imide and the surface fluorination products of the Al7N7 and Al4C4N4 cores

Reaction of RCN with an excess of AlH₃·NMe₃ in boiling toluene proceeds with the evolution of trimethylamine and provides an unusual heptameric aluminum imide (RCH₂NAlH)₇ (R=1-adamantyl) (1). Compound 1 is the second heptameric aluminum imide characterized by structural analysis. Compound 1 reacts with Me₃SnF to yield a mixture of partially fluorinated products of average composition (RCH₂NAl)₇F_2.26H_4.74 (2). The molecular structures of 1 and 2 show that both have an asymmetric Al₇N₇ core. Within the core, each aluminum atom binds to three nitrogen atoms in such a way that a cage-like structure is formed. The size dependent influence of the ligands on the AlN core formation is discussed. We also report on a tetrafluoro compound (t-BuNCH₂AlF)₄ (3) with terminal AlF bonds.     

A combined diffraction (XRD, electron and neutron) and electrical study of Na3MoO3F3

Na₃MoO₃F₃, a member of the A₂BM^VIO₃F₃ family of elpasolite-related oxyfluorides, has been prepared by the reaction of NaF with MoO₃ at 650°C. It is shown by a combined X-ray, electron and neutron diffraction study, that the true symmetry of Na₃MoO₃F₃ is not monoclinic (pseudo-orthorhombic) as previously reported but instead triclinic (metrically rhombohedral) P1. The superstructure unit cell is given by a=−a_R+b_R, b=c_R, c=(a_R+b_R+c_R), when expressed with respect to the underlying rhombohedral parent structure. Neutron diffraction refinement of the rhombohedral sub-structure shows O and F to be fully ordered with alternate (111)_R planes being occupied by O and then F. The nature of the distortion away from the high temperature parent structure is consistent with a combination of φφφ type rotations of the octahedral framework together with ppp type displacements of the octahedral cations, which is not observed in any of the closely related A₂BM^VIO₃F₃ family members. Bond valence arguments are used to give a plausible explanation for this difference in behavior.     

Non-covalent immobilization of C60 on gold surfaces by SAMs of porphyrin derivatives

Three porphyrin derivatives, one containing thioctic ester groups (3) and the other two with thioether chains (4 and 5), were synthesized. The cyclic voltammograms of the porphyrin compounds exhibit two reversible reduction processes and one reversible oxidation. Stable self-assembled monolayers (SAMs) of the porphyrin compounds were formed on gold surfaces. Non-covalent immobilization of C₆₀ was accomplished upon incubation of some of the porphyrin SAMs in solutions of C₆₀.     

Novel solvent-free reaction of C60 with active methylene compounds in the presence of Na2CO3 under high-speed vibration milling

Inorganic base, Na₂CO₃, was utilized to replace organic base, DBU, in the Bingel reaction employing diethyl bromomalonate under the mechanochemical ‘high-speed vibration milling’ conditions to give the cyclopropanated C₆₀1 in high yield. In contrast, reactions of C₆₀ with diethyl malonate and ethyl acetoacetate in the presence of Na₂CO₃ under HSVM conditions afforded 1,4-bisadduct 2 and dihydrofuran-fused C₆₀ derivative 3, respectively.     

The first N-alkyl-N′-polyfluorohetaryl sulfur diimide

The first AlkNSNHet_F sulfur diimide 6 (Alk=adamant-1-yl, Het_F=2,3,5,6-tetrafluoropyrid-4-yl) was prepared by trapping of the corresponding alkylthiazylamide [AlkNSN]⁻3 with pentafluoropyridine, followed by X-ray structural characterization. For 6, the Z,E configuration was found. From the reaction of 3 with octafluoronaphthalene, hexafluorinated naphthothiadiazole 7 was isolated along with the parent AlkNH₂.     

Synthesis of dibenzo-[b,f][1,5]diazocine-based hosts and their assembly behaviors with C60

Diaryl[b,f][1,5]diazocine-based macrocycles 5 and 6 with inner cavities have been synthesized via Hay coupling method. Single crystal of 5 shows that it forms a dimeric aggregate via the weak intermolecular interactions between two adjacent rings, which is rarely reported in such macrocycles. Moreover, SEM results reveal that both macrocycles 5 and 6 assemble with C₆₀ to form well-ordered fullerene-based nano-rod structures.     

Transition metal carbene chemistry 6: Kinetic studies of the reactions of hydroxide ion with (CO)5MoC(XCH2CH2OH)(C6H5) (X = O and S) and (CO)5WC(OCH2CH2OH)(C6H4-Z)

A kinetic study of the reaction of hydroxide ion with (CO)₅MoC(XCH₂CH₂OH)(C₆H₅) (X = O for Mo-OR, and X = S for Mo-SR), and (CO)₅WC(OCH₂CH₂OH)(C₆H₄-Z) (W-OR(Z)) is reported. The results are consistent with a pathway in basic solution that involves rapid deprotonation of the OH group followed by rate-limiting cyclization. The parameter k₁K^OH for the reaction of W-OR(Z) was determined as a function of the phenyl substituents. They were found to correlate well with the Hammett equation. The dependence of the reactivity on the metal atoms in the complexes M-OR (M = Cr, Mo and W) shows that the reactivity decreases slightly down the group of the Periodic Table, while for M-SR the reactivity increases slightly down the group. A plausible explanation of these results is offered based on electronegativity values of the metal atoms. The much higher ρ(k₁K^OH) value for W-OR(Z) over W-SR(Z) arises mainly due to the stabilization of the reactant carbene complex by the stronger π-donor effect of oxygen over sulfur.