Synthesis of tris(cyclopentadienyl)zirconium tetrakis(pentafluorophenyl)borate

Russian Chemical Bulletin - An efficient procedure for the synthesis of tris(cyclopentadienyl)zirconium tetrakis-(pentafluorophenyl)borate [Cp3Zr][B(C6F5)4] was suggested based on the reaction of...     

Ring-opening reactions of nonactivated aziridines catalyzed by tris(pentafluorophenyl)borane

The ring-opening reactions of nonactivated aziridines with amine nucleophiles are efficiently catalyzed by tris(pentafluorophenyl)borane leading to derivatives of trans-1,2-diamines in high yields. A mechanistic investigation of the reaction suggests that in situ formed [(C(6)F(5))(3)B(OH(2))].H(2)O catalyzes the opening through a Br?nsted acid manifold.     

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.     

Tripodal borate ligands from tris(dimethylamino)borane: the first synthesis of a chiral tris(methimazolyl)borate ligand, and the crystal structure of a single diastereomer pseudo-C3-symmetric Ru(II) complex

The activation of tris(dimethylamino)borane towards reaction with a chiral methimazole by N-methylimidazole has been used to prepare the first example of a chiral tris(methimazolyl)borate ligand. Coordination of this neutral ligand to Ru(II) has been achieved by reaction with [(p-cymene)RuCl(2)](2) to provide a single diastereomer complex in which the chirality of the methimazolyl substituents dictate the chirality of the bicyclo[3.3.3]cage formed by the ligand on coordination to the metal. The alternative approach to chiral tris(methimazolyl)borate ligands involving the introduction of a chiral group onto the boron atom has been explored by replacing N-methylimidazole in the above reaction by chiral oxazolines as activating bases in reaction with simple methimazole. However, although the B(NMe(2))(3) is activated to reaction with methimazole by these oxazolines, an intramolecular oxazoline ring-opening by a coordinated methimazolyl sulfur occurs and prevents the successful synthesis of these ligands.     

Oxo-molybdenum(VI,V,IV) complexes of the facially coordinating tris(mercaptoimidazolyl)borate ligand: synthesis, characterization, and oxygen atom transfer reactivity

A series of monooxo-Mo(IV,V) and dioxo-Mo(VI) complexes of the "soft" tripodal ligand, sodium tris(mercaptoimidazolyl)borate (NaTm(Me)), have been synthesized as potential oxygen atom transfer (OAT) models for sulfite oxidase. Complexes have been characterized by X-ray crystallography, cyclic voltammetry, and EPR, where appropriate. Oxygen atom transfer kinetics of Tm(Me)MoO(2)Cl, both stoichiometric and catalytic, have been studied by a combination of UV-vis and (31)P NMR spectroscopies under a variety of conditions. OAT rates are consistent with previously established relationships between redox potential/reactivity and mechanistic studies. The analysis of these complexes as potential structural and functional analogues of relevance to molybdoenzymes is further discussed.     

Metal and solvent‐free cyanosilylation of carbonyl compounds with tris(pentafluorophenyl)borane

A highly effective method of the cynaosilylation of aldehydes and ketones with TMSCN in the presence of catalytic amount of B(C₆F₅)₃ [tris(pentafluorophenyl)borane] has been developed. Cyano transfer from TMSCN to carbonyl group proceeds at room temperature under solvent‐free conditions. Various alehydes and ketones have been converted into the corresponding trimethylsilylether within short reaction times with excellent yield under mild conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Unusual reactivity of tris(pyrazolyl)borate zirconium benzyl complexes

The synthesis and reactivity of [Tp*Zr(CH2Ph)2][B(C6F5)4] (2, Tp* = HB(3,5-Me2pz)3, pz = pyrazolyl) have been explored to probe the possible role of Tp'MR2+ species in group 4 metal Tp'MCl3/MAO olefin polymerization catalysts (Tp' = generic tris(pyrazolyl)borate). The reaction of Tp*Zr(CH2Ph)3 (1) with [Ph3C][B(C6F5)4] in CD2Cl2 at -60 degrees C yields 2. 2 rearranges rapidly to [{(PhCH2)(H)B(mu-Me2pz)2}Zr(eta2-Me2pz)(CH2Ph)][B(C6F5)4] (3) at 0 degrees C. Both 2 and 3 are highly active for ethylene polymerization and alkyne insertion. Reaction of 2 with excess 2-butyne yields the double insertion product [Tp*Zr(CH2Ph)(CMe=CMeCMe=CMeCH2Ph)][B(C6F5)4] (4). Reaction of 3 with excess 2-butyne yields [{(PhCH2)(H)B(mu-Me2pz)2}Zr(Cp*)(eta2-Me2pz)][B(C6F5)4] (6, Cp* = C5Me5) via three successive 2-butyne insertions, intramolecular insertion, chain walking, and beta-Cp* elimination.     

Triarylamines with branched multi-pyridine groups: modulation of emission properties by structural variation,solvents, and tris(pentafluorophenyl)borane

Six triarylamine derivatives 1–6 with branched multi-pyridine substituents were prepared and characterized. These compounds are distinguished by the substituent on one of the phenyl group with NO2 for 1, CN for 2, Cl for 3, p-C6 H4 OMe for 4, OMe for 5,and NMe2 for 6, respectively. As revealed by single crystal X-ray analysis, these substituents play an important role in determining the configuration of the triarylamine framework and the crystal packing of 1–6. The emission properties of these compounds were examined in different solvents(toluene, CH2 Cl2, acetone, tetrahydrofuran(THF), and N,N-dimethylformamide(DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound 5 in CH2 Cl2. Compounds 1 and 6 show apparent aggregated enhanced emissions in acetone/H2 O.The emission properties of these compounds were further modulated by the addition of tris(pentafluorophenyl)borane. In addition, density functional theory(DFT) and time-dependent DFT(TDDFT) calculations have been performed on the ground and singlet excited states to complement the experimental findings.     

Synthesis and structural characterization of carbon-centered tris(pentafluorophenyl)silyl derivatives

A general method for the synthesis of carbon-centered tris(pentafluorophenyl)silyl derivatives (RSi(C₆F₅)₃) by reaction of trichlorosilanes (RSiCl₃) with pentafluorophenylmagnesium bromide was described. The crystal structures of obtained compounds were studied by X-ray diffraction analysis (7 structures). The peculiarities of crystal packing were analyzed by means of DFT calculations.     

Bis(allyl)gallium cation, tris(allyl)gallium, and tetrakis(allyl)gallate: synthesis, characterization, and reactivity

A series of cationic, neutral, and anionic allylgallium complexes has been isolated and fully characterized. It includes neutral [Ga(η(1)-C(3)H(5))(3)(L)] (1, L = THF; 2, L = OPPh(3)), cationic [Ga(η(1)-C(3)H(5))(2)(THF)(2)](+)[A](-) (3, [A](-) = [B(C(6)F(5))(4)](-); 4, [A](-) = [B(C(6)H(3)Cl(2))(4)](-)), as well as anionic [Cat](+)[Ga(η(1)-C(3)H(5))(4)](-) (5, [Cat](+) = K(+); 6, [Cat](+) = [K(dibenzo-18-c-6](+); 7, [Cat](+) = [PPh(4)](+)). Binding modes of the allyl ligand in solution and in the solid state have been studied comparatively. Single crystal X-ray analyses revealed a four-coordinate neutral gallium center in 2, a five-coordinate cationic gallium center in 4 and [4·THF], and a four-coordinate anionic gallium center with a bridging μ(2)-η(1):η(2) coordination mode of the allyl ligand in 6. The reactivity of this series of allylgallium complexes toward benzophenone and N-heteroaromatics has been investigated. Counterion effects have also been studied. Reactions of 1 and 5 with isoquinoline revealed the first examples of organogallium complexes reacting under 1,2-insertion with pyridine derivatives.     

Intra- and intermolecular N-H...F-C hydrogen-bonding interactions in amine adducts of tris(pentafluorophenyl)borane and -alane

The reaction between B(C(6)F(5))(3) and NH(3)(g) in light petroleum yielded the solvated adduct H(3)N.B(C(6)F(5))(3).NH(3). Treatment with a second equivalent of B(C(6)F(5))(3) afforded H(3)N.B(C(6)F(5))(3). Attempts to prepare the analogous alane adduct were unsuccessful and resulted in protolysis. Related compounds of the form R'R' 'N(H).M(C(6)F(5))(3) were synthesized from M(C(6)F(5))(3) and the corresponding primary and secondary amines (M = B, Al; R' = H, Me, CH(2)Ph; R' ' = Me, CH(2)Ph, CH(Me)(Ph); R'R' ' = cyclo-C(5)H(10)). The solid-state structures of 13 new compounds have been elucidated by single-crystal X-ray diffraction and are discussed. Each of the borane adducts has a significant bifurcated intramolecular hydrogen bond between an amino hydrogen and two o-fluorines, while N-H...F-C interactions in the alane adducts are weaker and more variable. (19)F NMR studies demonstrate that the borane adducts retain the bifurcated C-F...H...F-C hydrogen bond in solution. Compounds of the type R'R' 'N(H).M(C(6)F(5))(3) conform to Etter's rules for the prediction of hydrogen-bonding interactions.     

Synthesis and structures of tris(pentafluorophenyl)silylamines

Tris(pentafluorophenyl)silylamines were synthesized by silylation of amines and imines with (C₆F₅)₃SiCl or (C₆F₅)₃SiOTf in the presence of triethylamine. The crystal structures of the (C₆F₅)₃SiN(H)CH₂Ph and (C₆F₅)₃SiN(CH=CMe₂)CH₂Ph compounds were studied by X-ray diffraction. The crystal packings were analyzed by quantum chemical calculations in terms of the density functional theory (PBE exchange-correlation functional). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1345–1352, July, 2007.     

Syndiospecific living polymerization of 4-methylstyrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminium catalytic system

The polymerization of 4-methylstyrene with the (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe₃)/tris(pentafluorophenyl)borane (B(C₆F₅)₃)/trioctylaluminium (AlOct₃) catalytic system at –20°C was carried out. The number-average molecular weight (M_n) of the polymers increased linearly with increasing monomer conversion. The propagating chain ends were successfully reacted with tert-butyl isocyanate, and the M_n of the polymer determined by ¹H NMR was in good agreement with the M_n determined by GPC measurement. It is concluded that this catalytic system promoted the syndiospecific living polymerization of 4-methylstyrene.     

Sterically bulky tris(triazolyl)borate ligands as water-soluble analogues of tris(pyrazolyl)borate

The recently synthesized 3-tert-butyl-5-methyl-1,2,4-triazole reacted with KBH4 to give the new potassium tris(3-tert-butyl-5-methyl-1,2,4-triazolyl)borate K(Ttz(tBu,Me)) ligand. Ttz(tBu,Me) formed a four-coordinate (Ttz(tBu,Me))CoCl complex and five-coordinate (Ttz(tBu,Me))CoNO3 and (Ttz(tBu,Me))ZnOAc complexes. When these complexes were compared to their Tp(tBu,Me) analogues, it was found that Ttz(tBu,Me) resulted in negligible steric differences. K(Ttz(tBu,Me)) is more water-soluble than K(Tp(tBu,Me)), so bulky tris(triazolyl)borate ligands should lead to functional models for enzyme active sites in an aqueous environment and the creation of water-soluble analogues of Tp catalysts.     

Synthesis,characterization, antifungal,antibacterial, and antitumor activities of some tris(pentafluorophenyl)arsenic(V) derivatives

A series of tris(pentafluorophenyl) arsenic(V) derivatives of the type (C₆F₅)₃AsL₂, (C₆F₅)₃As(Cl)(L) [L =  OCOC₆H₄(o‐OH),  OCOC‐(OH)(C₆H₅)₂, and 2‐(6‐OCH₃C₁₀H₆)CH(CH₃) COO ], and cycloarsenates, (R = C₆H₅, p‐CF₃C₆H₄, and p‐OCH₃C₆H₄) have been isolated and characterized by elemental analysis and spectroscopic data (infrared; ¹H, ¹⁹F, and ¹³C NMR). These compounds were screened for their in vitro antifungal, antibacterial, and antitumor activities and were found to show moderate to significant activity. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:181–187, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20593     

Fluorotris(trifluoromethylsulfonyl)methane: synthesis, characterization and reactivity

The hitherto elusive title compound was synthesized and characterized with the aim to study its potential as a carbon-based (“CF-type”) electrophilic fluorination reagent. A detailed discussion of its structure, properties and reactivity is based on experimental studies as well as on molecular modeling.     

Networks based on hydrogen-bonds containing phosphorus anions and tris(3,5-dimethylpyrazolyl)borate nickel(II) moieties

Five structural kinds of nickel hydrogen-bonded networks containing hydrotris(3,5-dimethylpyrazolyl)borate ligands (Tp^∗) have been elucidated by X-ray diffraction, [Tp^∗Ni(OH₂)₃][(p-NO₂C₆H₄O)₂PO₂] (4), [Tp^∗Ni(OH₂)₃][Me₂PO₂]·Me₂P(O)OH (5), [Tp^∗Ni(OH₂)₃][(nBuO)₂PO₂]·0.5H₂O (6), [(Hpz)Tp^∗Ni(OH₂)₂][(Ph)PO₂OH] (7) and [Tp^∗Ni(OH₂)₂(Me₂PO₂)] (8). The most relevant supramolecular feature of complexes 4-8 is all of them form coordination networks based on hydrogen bonds between water molecules and phosphate, phosphonate or phosphinate anions. These hydrogen bonds are formed within the monomer units in addition to connect monomers along the chains. Their behaviors in solution were investigated by one- and two-dimensional ¹H NMR techniques.     

Reactivity of thallium tris[tris(pentafluorophenyl)germyl] mercurate

Metallic lithium and dibenzenechromium displace thallium from (R^f₃Ge)₃HgTl·1.5DME (R^f = C₆F₅, DME = 1,2-dimethoxyethane) to give (R^f₃Ge)₃HgLi·3DME and [(R^f₃Ge)₄Hg][Cr(C₆H₆)₂]₂, respectively. Reactions of thallium germylmercurate with halides of metals and organometallics in DME/EtOH solution produce ionic compounds of [(R^f₃Ge)₃Hg]^? M⁺ type, which (depending on “M”) (a) may be isolated as pure compounds, (b) disproportionate, (c) form covalent derivatives R^f₃Ge-m or (d) undergo alcoholysis. A general scheme for the reactions has been proposed.     

New approach to the synthesis of tris(perfluoroalkyl)borane adducts with dialkylamines

A convenient synthetic approach to the adducts (C _n F_2n+1)₃BNHR₂ (n = 2–4, 6; R = Me, Et) was developed, based on the reaction of lithium perfluoroalkyls with dichloro(dialkylamino)boranes at temperatures below ?90°C. The target products can be synthesized with preparative yields of 50–90%.