Anion allosteric effect in the recognition of tetramethylammonium salts by calix[4]arene cone conformers.

Rigid calix[4]arene cone conformers, which are efficient receptors for quaternary ammonium salts, are usually obtained through the functionalization of their lower rim with suitable groups. Using flexible cone conformer of calix[4]arene, bearing four 4-hydroxybenzyl groups as cooperative and rigidifying structural elements at the upper rim of the calix, which act as anion binding groups, a new heteroditopic cavitand, 7, was synthesized. Whereas the tetramethoxy derivative 8 does not show any complexing ability, its tetrahydroxy analogue 7 recognizes tetramethylammonium salts with high efficiency. The binding abilities of this new receptor toward a series of tetramethylammonium salts (tosylate, chloride, acetate, trifluoroacetate, and picrate) have been investigated in CDCl(3) solution and compared to the monotopic and rigidified, through the lower rim, cone biscrown-3-calix[4]arene 9. The results obtained confirmed that in CDCl(3) ion pairing strongly affects binding. In particular, the rigid monotopic receptor 9 experiences good efficiency toward tetramethylammonium salts having anions with low ion-pairing ability such as trifluoroacetate or picrate. On the contrary, for the new heteroditopic cavitand 7, a reverse order of efficiency was found. In the latter case a different complexation mode was hypothesized in which the tetramethylammonium cation is deeply entrapped into the host cavity and its counteranion participates to the recognition process by coordination via hydrogen bonding by the four OH groups. To further support the role of the anion in the recognition process, a "dual host" approach, employing 7 or 9 in the presence of a specific receptor for chloride anion (10), was utilized. Molecular modeling studies confirmed that in the complexes formed by 7 and TMA salts the counteranion is involved in hydrogen bonding with the host OH groups and that the guests are bound as ligand-separated ion pairs.     

Synthesis of 4-Alkyl-4-alkoxybutenolides Having Unsaturated Side Chains via Chromium Carbene Complex Photochemistry: (+)-Cerulenin

The photochemical reaction between optically active ene carbamates and chromium alkoxycarbene complexes containing unsaturated aliphatic side chains was further developed. Although remote olefinic groups, including conjugated dienes, were tolerated, a homoallylic side chain underwent intramolecular reaction to give a strained cyclobutanone. (+)-Cerulenin was synthesized utilizing the photochemical reaction of an alkynylcarbene complex with an optically active ene carbamate and the bis(pi-crotyl)nickel halide alkylation of a vinyl bromide as key steps.     

Synthesis of fluorinated geminal diisocyanides stabilized on a transition metal

Chromium complexes of the geminal diisocyanides bis(pentacarbonyl)-μ-2,2-diisocyano-1,1,1,3,3,3-hexafluoropropane)dichromium 1a and bis(pentacarbonyl)-μ-2,2-diisocyano-1,1,1,3,3-pentafluorobutane)dichromium 1b were obtained by radical alkylation of pentacarbonylcyanochromate besides pentacarbonyl(2-isocyano-1,1,1,3,3,3-hexafluoropropane)chromium 2a and pentacarbonyl(2-isocyano-1,1,1,3,3-pentafluorobutane)chromium 2b, respectively. Pentacarbonyl(2-isocyano-1,1,1,2,3,3,3-heptafluoropropane)chromium 2c was prepared analogously. The crystal and molecular structures of 1a and b were determined by X-ray diffraction.     

Correlation of crystal parameters with vibrational data of tetramethylammonium fluorocompounds

Examination of the solid state infrared spectra of the tetramethylammonium cation in ten salts shows correlation of infrared spectral properties with C-H…X hydrogen bonding and crystal habits in these tetramethylammonium salts. In this research a number of complexes of tetramethylammonium cation have been synthesized and the structures of five of them have been analyzed by X-ray single crystal diffraction. The IR predicted crystal habits are comprised by XRD data. The C-H stretching region characteristic hydrogen bonding shifts in the above salts. A good relation between two data has been found.     

Synthesis and characterization of novel 4-nitro-2-(octyloxy)phenoxy substituted symmetrical and unsymmetrical Zn(II), Co(II) and Lu(III) phthalocyanines

Compounds 3 and 4 have been prepared by the reaction of 4-nitrocatechol 1 and 4-nitrophthalonitrile 2 by a common method, aromatic nucleophilic subtitution of the nitro group in 4-nitrophthalonitrile. Starting from 4 and 1-bromooctane, their alkylation reaction gave compound 5. Zn(II) 8, Co(II) 9 and Lu(III) 10 complexes were synthesized from the corresponding metal salts by the tetramerization of compound 5. Compound 7 was prepared by the statistical condensation of 5 and 4,5-bis(hexylthio)phthalonitrile 6 with CoCl₂ · 6H₂O in dry dimethylformamide. The new compounds were characterized by FT-IR, UV/Vis, NMR and mass spectra. The electrochemical properties of the complexes were also investigated by cyclic voltammetry in non-aqueous medium. The effect of temperature on the dc conductivity and the impedance spectra of spin coated film of the compounds was investigated at temperatures between 295 and 433 K and in the frequency range 40–10⁵ Hz. Thermally activated conductivity dependence on temperature was observed for all compounds.     

New metal aminocarbene-substituted cyclopentadienyliron half sandwich complexes

Some new half sandwich cyclopentadienyl aminocarbene complexes were prepared by treatment of the corresponding alkoxycarbene complexes with primary and secondary amines, including enantiopure chiral aminoalcohols and amines with acetyl, phosphine, alkene, and alkyne functionalities, all of which proved to be compatible with the substrates. In two cases the complexes were crystallographically characterized indicating that the metal–carbon double bond is – in contrast to some alkoxycarbene analogues – not in conjugation with the cyclopentadienyl π-system in the solid state. Some of the complexes were characterized by cyclic voltammetry showing similar behavior as the corresponding alkoxycarbene complexes. The complexes are the first examples of half sandwich complexes with a cyclopentadienyl-aminocarbene ligand system.     

S-alkylation and S-amination of methyl thioethers--derivatives of closo-[B(12)H(12)](2-). synthesis of a boronated phosphonate, gem-bisphosphonates, and dodecaborane-ortho-carborane oligomers

A variety of S-alkylated products was prepared by alkylation of methyl thioethers [MeSB(12)H(11)](2-) (5), [1-(MeS)-2(7,12)-(Me(2)S)B(12)H(10)](-) (6-8), and [1,2(7,12)-(MeS)(2)B(12)H(10)](2-) (9-11) with alkyl halides and tosylates in acetonitrile. Since these methyl thioethers can be prepared easily in B-10-enriched form on a large scale and due to their chemical versatility, they are potentially very attractive boron entities for the design and synthesis of therapeutics for boron neutron capture therapy of cancer. It was found that alkylation of 6-8 can be complicated by an equilibrium which establishes between, on the one hand, one of the former species and, on the other hand, 1,2(7,12)-(Me(2)S)(2)B(12)H(10) (2-4) and [1,2(7,12)-(MeS)(2)B(12)H(10)](2-) (9-11). A boronated phosphonate 1-(MeS(CH(2))(4)P(O)(OEt)(2))-7-(Me(2)S)B(12)H(10) (14g) and a gem-bisphosphonate 1-(MeS(CH(2))(3)CH[P(O)(OEt)(2)](2))-7-(Me(2)S)B(12)H(10) (14h) were prepared from thioether 7 and the corresponding iodide and tosylate, respectively, and subsequently converted to their sodium salts. The propargyl sulfonium salts obtained by alkylation of thioethers 7, 8, 10, and 11 with propargyl bromide have been further converted to two- and three-cage oligomers containing both ortho-carborane and dodecaborane moieties. Methyl thioethers derived from closo-[B(12)H(12)](2-) are excellent participants in Michael addition reactions in the presence of a strong acid. The sulfonium salts with tertiary alkyl and vinyl substituents have been prepared by this method. Methyl thioethers 5-11 react with hydroxylamine-O-sulfonate yielding the corresponding aminosulfonium salts, albeit in lower yields as compared to those in the alkylation reactions. Several derivatives of methyl thioethers 5-11 have been characterized by single-crystal X-ray diffraction.     

Convenient synthesis of dithiafulvene carbene complexes as potential precursors of extended TTF

The condensation of α-carbanion of Fischer-type carbene complex with 2-thiomethyl-1,3-dithiolium salts 1 gave new heterocyclic organometallic carbenes 2 potentially precursors of extended TTF. Reaction of allylic carbanion 4 derived from (methoxypropenyl)pentacarbonyl carbene complex afforded a mixture of monoheterocyclic condensation products 7 and diheterocyclic carbene complexes 8 produced from successive α and γ attacks of the heterocyclic cations.     

Direct synthesis of molecular self-complexes in the indole series

A method for the alkylation of 3-unsubstituted indoles by means of 1-(-haloalkyl)-pyridinium salts via the Friedel-Crafts reaction with the aid of complex catalysts, viz., complexes of zinc, tin, and titanium chlorides with pyridine, was developed. On the basis of a study of the electronic spectra of the resulting 1-(3-indolyl-alkyl)pyridinium salts it was shown that they are molecular self-complexes. The stabilities of the molecular self-complexes were investigated as a function of the length of the alkyl chain and the character of the substituents in the indole ring.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1222–1226, September, 1980.     

Electrochemical surface derivatization of glassy carbon by the reduction of triaryl- and alkyldiphenylsulfonium salts

The range of materials susceptible to electrochemically assisted grafting onto carbon materials has been expanded to include a new group of compounds. This new approach is based on the reduction of symmetrical or unsymmetrical triarylsulfonium salts and alkyldiphenylsulfonium salts. Our findings suggest that it is possible to form layers of aryl moieties on the surface and that the unsymmetrical triarylsulfonium salts cleave upon reduction in a direction dictated by the substituent on the rings (i.e., (4-methoxyphenyl)diphenylsulfonium salt leads to a film made predominantly of phenyl groups, whereas (4-chlorophenyl)diphenylsulfonium salt leads to a mixture of phenyl and chlorophenyl groups). These relationships may be understood by considering the inductive nature of the substituent with regard to the aryl-S bonds and are supported by preparative experiments. Upon reduction, the alkyldiphenylsulfonium salts are found to cleave almost exclusively to an alkyl radical and diphenyl sulfide. As judged from the electrochemical blocking properties of the films made from such species, either relatively thick or compact films are formed. The mass spectrometric analysis indicates that the films are made of a combination of alkyl and aryl groups and possibly related structural derivatives. Importantly, our findings provide evidence that it is possible to graft electrode surfaces with reactive aryl radicals even using precursors reduced at potentials that are substantially more negative than the estimated reduction potential of the grafting radical.     

Pentacarbonyl(organylphenoxycarben)-Komplexe des Chrom(0) und Wolfram(0)

Pentacarbonyl(acetoxyorganylcarbene) complexes of chromium(0) and tungsten(0) react with sodium phenolate to give pentacarbonyl(organylphenoxycarbene)chromium(0) and tungsten(0).     

Trifluoromethylation of non-activated aldimines with trimethyl(trifluoromethyl)silane in the presence of tetramethylammonium fluoride: A closer look into the reaction route

The reactions of non-activated aldimines with trimethyl(trifluoromethyl)silane and 1 equiv. of tetramethylammonium fluoride proceed via the formation of tetramethylammonium amides which were identified by low-temperature ¹⁹F NMR experiments. Consecutive reactions of the salts formed in situ with electrophiles yielded trifluoromethylated amines. Fluoride elimination is observed in the absence of electrophilic substrates leading to the formation of difluoromethylated ketimines.     

Detection and reactivity of a palladium alkoxycarbene

A characterful carbene: The high electrophilicity of a genuine palladium alkoxycarbene, obtained by transmetalation, is evident in its reactivity. Nucleophilic attack on two electrophilic centers (red) is observed. Alkyl abstraction and addition to the carbene carbon by different nucleophiles occur. This palladium(II) alkoxycarbene also undergoes comproportionation with palladium(0) to give an unprecedented palladium(I) dimeric carbene (see scheme).     

The synthesis and coordination properties of new macrocyclic polyethers

A new type of macrocyclic polyethers has been synthesized. It consists of an azacrown ether as mother ring, e.g. 1,7-dioxa-4,10-diaza-cyclododecane (1a) or 1,7,10,16-tetraoxa-4,13-diazacycloocatadecane (1b), and two side chains attached on the two nitrogen atoms of 1a or 1b. A number of these new crown ethers are obtained by alkylation of the two secondary amino groups of 1a or 1b with corresponding halides, BrCH₂(CH₂OCH₂)_nCH₂OR, in the presence of potassium carbonate. The crown-alkali metal complex thus obtained is hydrolyzed by acid. In order to obtain pure crown ether the reaction mixture is treated with tetramethylammonium hydroxide and followed by solvent extraction. The ability of complexing alkali cations of macrocyclic polyethers in terms of the equilibrium constant have been studied by the method of solubilities of salts in chloroform. It is shown that the size of the mother ring, the number of oxygen atoms either in the ring or in the side-chains, and the ionic radius of the alkali metal are the factors governing the stability of the metal complexes. Most of these new crown ethers possess high ability for alkali metal complexation some of them, such as N,N′- di-β-methoxyethyl-1,7-dioxa-4,10-diaza-cyclododecanc (13a), possesses higher selectivity for Na+ and K+ ions than 18-crown-6- and 4,4′(5′)-dimethylbenz-30-crown-10.     

Syntheses of halogenated ethenyl isocyanide chromium complexes as organometallic precursor molecules for ethenyl and ethynyl isocyanides

The radical alkylation of tetraethylammonium pentacarbonyl(cyano)chromate 1 yielded the halogenated ethyl isocyanide complexes [(CO)5Cr(CN-CClX-CClYF)] 3 (a, X= Cl, Y= F; b, X = F, Y= F and c, X=Y= Cl). Dehalogenation of 3 using zinc in diethyl ether gave [(CO)5Cr(CN-CX=CFY)] 4. The compounds 4a, b reacted with various nucleophiles exclusively at the difluoromethylene group. The unstable phosphorane 5, which is formed on reaction of 4b with trimethylphosphane, decomposed thermally and on hydrolysis yielding pentacarbonyl(1,2-difluoroethenyl isocyanide)chromium (6). The cyano substituent can be introduced in the beta position of the isocyanide function by reaction of 4a, b with potassium cyanide, leading to the formation of [(CO)5Cr(CN-CX=CF-CN)] (7). Reactions of 4a, b with organolithium or organomagnesium compounds yielded [(CO)5Cr(CN-CX=CF-R)] (8) and [(CO)5Cr(CN-CF=CF-C...C-CF=CF-NC)Cr(CO)5] (10). The trimethylsilyl group in 8a, b, d could be removed by a solution of potassium carbonate in methanol leading to [(CO)5Cr(CN-CX=CF-Cn-H)] (11) (n=2,4). Octacarbonyldicobalt reacted with 8e under coordination of the C-C triple bond to the hexacarbonyldicobalt fragment, resulting in the cluster compound 12. The crystal and molecular structure of 8i, 11 a, b, and 12 were elucidated by X-ray crystallography. The alkenyl and alkynyl isocyanides CN-CCl=CF2 (13a), CN-CF=CF2 (13b), CN-CCl=CClF (13c), CN-CF=CFH (14), CN-CC-H (15), CN-CC-CN (16), and CN-CCl=CF-CN (17) were obtained by flash vacuum pyrolysis of 4a, 4b, 4c, 6, and 7a, respectively.     

Reactions of 2H-tellurochromene

2-H-Tellurochromene is characterized by reactions (halogenation, alkylation, and complex-formation) which result in an increase in the coordination number of the tellurium atom to 4 or 3, to give -telluranes, telluronium salts, and complexes with metal salts. Oxidation of 2-H-tellurochromene with trityl perchlorate affords tellurochromyllium perchlorate, and with dichromate 2-formylbenzo [b] tellurophene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1050–1054, August, 1988.     

Unexpected stabilization of the heterocyclic form of oxidized dithizone: Synthesis and molecular structures of chromium and tungsten 5-mercapto-2,3-diphenyltetrazolium pentacarbonyls

New chromium and tungsten pentacarbonyl complexes with 5-mercapto-2,3-diphenyltetrazole coordinated through the sulfur atom (Cr-S, 2.4655(7) Å; W-S, 2.5755(13) Å) were synthesized and structurally characterized.     

Übergangsmetall-Komplexe des 1,1,3,3-Tetrakis(dimethylamino)-1λ5,3λ5-diphosphets

Transition Metal Complexes of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-Diphosphete 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3aλ⁵-diphosphete, 1 , reacts with W(CO)₆ to yield the isomeric complexes {1,1,3,3-tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete}(pentacarbonyl)tungsten 4 and {1,1,3,3-tetrakis(dimethylamino)-1,4-dihydro-1λ⁵,3λ⁵-[1,3]diphosphetium}(pentacarbonyl)tungsten 5 . With Cr(CO)₆ the complex {1,1,3,3-tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete}(pentacarbonyl)chromium 6 is formed. From the reaction products of Fe₃(CO)₁₂ and Fe₂(CO)₉ with 1 the complex {1,1,3,3-tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete}(pentacarbonyl)iron 7 could be isolated. Properties, nmr, ir and mass spectra of the new compounds are reported. 6 and 7 were characterized by X-ray structure determinations.     

Tetrakis(tetrahydrofuran-O)calcium-bis[pentacarbonyl(cyano)chromat(0)], -molybdat(0)] und -wolframat(0)]

Tetrakis(tetrahydrofuran- O )calcium bis[pentacarbonyl(cyano)chromate(0)], -molybdate(0)], and -tungstate(0)] The reaction of (THF)₂Ca[N(SiMe₃)₂]₂ with hexacarbonylchromium, -molybdenum, and -tungsten yields hexamethyldisiloxane and tetrakis(tetrahydrofuran-O)calcium bis[pentacarbonyl(cyano)chromate(0)] ( 1 ), -molybdate(0)] ( 2 ), and -tungstate(0)] ( 3 ), respectively. Compound 1 crystallizes in the centrosymmetric space group P 1, whereas the other two complexes 2 and 3 are isotypic (monoclinic, P2₁/n). In all these compounds the calcium atom is bonded to the nitrogen atoms of the cyano ligands and bent Ca–N–C fragments with angles of 158,3° ( 1 ), 161,2° ( 2 ), and 161,3° ( 3 ) are observed.     

Übergangsmetall-carben-komplexe: CXXXVIII. Neue übertragungsreaktionen von carbenliganden zur darstellung von gold-carben-komplexen

Chloroauric acid reacts with pentacarbonyl[(dimethylamino)ethoxycarbene]chromium(0) (I) to give trichloro[(dimethylamino)ethoxycarbene]gold(III) (IV), and with pentacarbonyl{(dimethylamino)[methoxy(phenyl)methyleneamino]carbene} complexes of molybdenum(0) (II) and tungsten(0) (III) to give chloro{(dimethylamino)[methoxy(phenyl)methyleneamino]carbene}gold(I) (VII) and trichloro{(dimethylamino)[methoxy(phenyl)methyleneamino]carbene}gold(III) (VIII). IV and VIII react with boron tribromide to give tribromo[(dimethylamino)ethoxycarbene]gold(III) (V) and tribromo{(dimethylamino)[methoxy(phenyl)methyleneamino]carbene}gold(III) (IX), which react with boron triiodide to yield the triiodogold complexes [(dimethylamino)ethoxycarbene]triiodogold(III) (VI) and {dimethylamino[methoxy(phenyl)methyleneamino]carbene} triiodogold(III) (X).